Draft Gore 2008 PAC

Four new papers discuss the relatiosnhip between solar activity and climate: one by Judith Lean (2010) in WIREs Climate Change, a GRL paper by Calogovic et al. (2010), Kulmala et al. (2010), and an on-line preprint by Feulner and Rahmstorf (2010). They all look at different aspects of how changes in solar activity may influence our climate.

The paper by Judith Lean (2010) has the character of a review article, summarizing past studies on the relationship between solar forcing and climate. The main message from her article is that the solar forcing probably plays a modest role for the global warming over the last 100 years (10% or less). It’s a nice overview, but I miss treatment of uncertainties.

Her analysis is based on the HadCRUT3 data, and I wonder if she would get similar results if she chose the GISTEMP or NCDC instead. The choice may in particular be relevant for the discussion of the temperatures after 1998.

Personally, I regard the data on solar activity before 1900 as quite uncertain too. The reason is that there are strange things happening to the solar cycle length in the shift from the 19th to the 20th century. Hence, any analysis based on the past centuries is uncertain because of suspect data quality in the early part of the record. Lean mentions that proxy-based records are uncertain, however.

Another source of uncertainty stems from the analysis itself – a regression analysis with chaotic data can easily yield misleading results. Gavin and I showed in a recent paper that multiple regression can produce strange results when applied to the global mean temperature and a number of forcings.

In other words, I think the reader may get the wrong impression from Lean (2010) that the link between solar activity and climate is better established than the data and methods suggest. Especially when she discusses forecasts for the near future (eg. for year 2014) – I fear that such a discussion can be misinterpreted and misused. However, that’s my view, and it does not necessarily mean that her paper is incorrect – quite the opposite, I think her main conclusions are sound (Her estimate of the solar contribution to the global warming over past century – 10% or less – is in good agreement with the figure Gavin and I got in our analysis).

The positive side is that the paper is probably clearer and more accessible without all these caveats. I also think she makes an interesting point when she discusses ‘fundamental puzzles’ associated with claims of strong solar role in terms of the past warming. She puts this into the context of climate sensitivity, arguing that it would imply that Earth’s climate be insensitive to well-measured increases in GHG concentrations and simultaneously excessively sensitive to poorly known solar brightness changes. Furthermore, Lean argues that it would also require that the Sun’s brightness increased more in the past century than at any time in the past millennium – a situation not readily supported by observations.

The paper of Calogovic et al. (2010) is a follow-up of a recent paper by Svensmark et al. (2009), looking into the claim that the cloud water content drops after a Forbush event. Their work involved estimating cosmic ray fluxes for the whole planet, and comparing it to local cloud information derived from satellites. They concluded that the Forbush events had no detectable effect on the clouds.

Moreover, they also argued that the analysis of Svensmark et al. (2009) gave unreliable results since it included a Forbush event on January 20, 2005 which was accompanied by a strong solar proton event. However, they did not explain explicitly why such proton events would disturb the measurements, but referred to another study by Laken et al. (2009) in Geophysical Research Letter. Laken et. al. only discusses the proton events briefly, and refers to a study by Fluckiger et al. (2005), who state that “The cosmic ray ground level enhancement (GLE) on January 20, 2005 is ranked among the largest in years, with neutron monitor count rates increased by factors of more than 50″.

But there is no reference to proton events in Fluckiger et al. (2005), so I’m not convinced that proton events will invalidate the analysis of Svensmark et al. (2009). Perhaps I’m missing something? Anyway, this is only a minor detail, and the rest of the analysis of Calogovic et al. (2010) seems more convincing. Their conclusion is supported by Kulmala et al. (2010): “galactic cosmic rays appear to play a minor role for atmospheric aerosol formation events, and so for the connected aerosol-climate effects as well”. Kulmala’s group in Finland boasts many world-renowned aerosol physicists.

The study by Kulmala et al. (2010) was based on near-ground measurements of aerosols, magnetic field, cosmic rays, sunlight intensity (solar radiation), and ionization over a 13-year long period (~1 solar cycle). They also used airborne Neutral cluster and Air Ion Spectrometer, LIDAR and Forward Scattering Spectrometer Probe measurements. They failed to detect any correlation between cosmic ray ionization intensity and atmospheric aerosol formation.

Feulner and Rahmstorf address a speculation stated by Lean: the possibility of solar forcing countering anthropogenic global warming. Their paper examines the effect a solar grand minimum (low solar activity similar to that inferred for the Maunder Minimum) would have on the global mean temperature by 2100. By accounting for a corresponding reduction in forcing for the future in a climate model study, they conclude that the effect is negligible (less than 0.3K compared to 3.7 – 4.5K if the SRES A1b or A2 emission scenarios were assumed).

So what can we learn from these articles? What we see is how science often works – increases in knowledge by increments and independent studies re-affirming previous findings, namely that changes in the sun play a minor role in climate change on decadal to centennial scales. After all, 2009 was the second-warmest year on record, and by far the warmest in the southern hemisphere, despite the record solar minimum. The solar signal for the past 25 years is not just small but negative (i.e. cooling), but this has not noticeably slowed down global warming. But there are also many unknowns remaining, and the largest uncertainties concern clouds, cloud physics, and their impact on climate. In this sense, I find it ironic that some people still rely on the cosmic rays argument as their strongest argument against AGW – it does involve poorly known clouds physics!

The Institute of Physics (IoP) recently made a splash in the media through a statement about the implications of the e-mails stolen in the CRU hack. A couple of articles in the Guardian report how this statement was submitted to an inquiry into the CRU hack and provide some background.

The statement calls for increased transparency, and expresses concerns about the public confidence in science if the transparency is absent. The IoP statement, however, fails to note that the issue of transparency is far more general applicable than just to mainstream climate science. It should also involve the critics of climate change, as noted by New Scientist.

The statement also fails to clarify what level of transparency they expect the climate scientists to reach. Which scientific discipline should we use as a role model? I know of none that is more transparent than climate science, and in large part that s due to the IPCC. Ironically, without this transparency, the climate-change deniers would not get as much ammunition. For instance, note how the attacks on the NASA GISTEMP product have become more vehement in recent months even though the code base and data have been available for years and clearly demonstrate that the criticisms are bogus.

Another question arises is whether the IoP follows its own recommendations in its own publications?

The statement of the IoP was made on the behalf of its 36000 members, but as a member of IoP myself, this came as a surprise. According to the Guardian, there was only a small group of people behind this, and other IoP members was obviously not very impressed. The IoP did, however, make a second statement after their initial one was misrepresented by the climate-change deniers (there is some confusion about versions).

The irony of this affair is that the IoP will not disclose who were responsible for the original statement, thus not living up to the standards they set for others.

Furthermore, it’s a paradox that the IoP based the statement on stolen private e-mail exchanges, while putting disclaimers about confidentiality, especially as it asks people to delete any e-mail before they go astray:

This email (and attachments) are confidential and intended for the addressee(s) only. If you are not the intended recipient please notify the sender, delete any copies and do not take action in reliance on it…

Transparency is essential for trust and confidence in science – as in all matters – but claims about lack of transparency are easy to make. It’s another question whether the alleged lack of transparency in climate science has had any impact on anyone’s ability to verify the science.

Methane is like the radical wing of the carbon cycle, in today’s atmosphere a stronger greenhouse gas per molecule than CO2, and an atmospheric concentration that can change more quickly than CO2 can. There has been a lot of press coverage of a new paper in Science this week called “Extensive methane venting to the atmosphere from sediments of the East Siberian Arctic Shelf”, which comes on the heels of a handful of interrelated methane papers in the last year or so. Is now the time to get frightened?

No. CO2 is plenty to be frightened of, while methane is frosting on the cake. Imagine you are in a Toyota on the highway at 60 miles per hour approaching stopped traffic, and you find that the brake pedal is broken. This is CO2. Then you figure out that the accelerator has also jammed, so that by the time you hit the truck in front of you, you will be going 90 miles per hour instead of 60. This is methane. Is now the time to get worried? No, you should already have been worried by the broken brake pedal. Methane sells newspapers, but it’s not the big story, nor does it look to be a game changer to the big story, which is CO2.

[Note: Edited Toyota velocities to reflect relative radiative forcings of anthropogenic CO2 and methane. David]

For some background on methane hydrates we can refer you here. This weeks’ Science paper is by Shakhova et al, a follow on to a 2005 GRL paper. The observation in 2005 was elevated concentrations of methane in ocean waters on the Siberian shelf, presumably driven by outgassing from the sediments and driving excess methane to the atmosphere. The new paper adds observations of methane spikes in the air over the water, confirming the methane’s escape from the water column, instead of it being oxidized to CO2 in the water, for example. The new data enable the methane flux from this region to the atmosphere to be quantified, and they find that this region rivals the methane flux from the whole rest of the ocean.

What’s missing from these studies themselves is evidence that the Siberian shelf degassing is new, a climate feedback, rather than simply nature-as-usual, driven by the retreat of submerged permafrost left over from the last ice age. However, other recent papers speak to this question.

Westbrook et al 2009, published stunning sonar images of bubble plumes rising from sediments off Spitzbergen, Norway. The bubbles are rising from a line on the sea floor that corresponds to the boundary of methane hydrate stability, a boundary that would retreat in a warming water column. A modeling study by Reagan and Moridis 2009 supports the idea that the observed bubbles could be in response to observed warming of the water column driven by anthropogenic warming.

Another recent paper, from Dlugokencky et al. 2009, describes an uptick in the methane concentration in the air in 2007, and tries to figure out where it’s coming from. The atmospheric methane concentration rose from the preanthropogenic until about the year 1993, at which point it rather abruptly plateaued. Methane is a transient gas in the atmosphere, so it ought to plateau if the emission flux is steady, but the shape of the concentration curve suggested some sudden decrease in the emission rate, stemming from the collapse of economic activity in the former Soviet bloc, or by drying of wetlands, or any of several other proposed and unresolved explanations. (Maybe the legislature in South Dakota should pass a law that methane is driven by astrology!) A previous uptick in the methane concentration in 1998 could be explained in terms of the effect of el Nino on wetlands, but the uptick in 2007 is not so simple to explain. The concentration held steady in 2008, meaning at least that interannual variability is important in the methane cycle, and making it hard to say if the long-term average emission rate is rising in a way that would be consistent with a new carbon feedback.

Anyway, so far it is at most a very small feedback. The Siberian Margin might rival the whole rest of the world ocean as a methane source, but the ocean source overall is much smaller than the land source. Most of the methane in the atmosphere comes from wetlands, natural and artificial associated with rice agriculture. The ocean is small potatoes, and there is enough uncertainty in the methane budget to accommodate adjustments in the sources without too much overturning of apple carts.

Could this be the first modest sprout of what will grow into a huge carbon feedback in the future? It is possible, but two things should be kept in mind. One is that there’s no reason to fixate on methane in particular. Methane is a transient gas in the atmosphere, while CO2 essentially accumulates in the atmosphere / ocean carbon cycle, so in the end the climate forcing from the accumulating CO2 that methane oxidizes into may be as important as the transient concentration of methane itself. The other thing to remember is that there’s no reason to fixate on methane hydrates in particular, as opposed to the carbon stored in peats in Arctic permafrosts for example. Peats take time to degrade but hydrate also takes time to melt, limited by heat transport. They don’t generally explode instantaneously.

For methane to be a game-changer in the future of Earth’s climate, it would have to degas to the atmosphere catastrophically, on a time scale that is faster than the decadal lifetime of methane in the air. So far no one has seen or proposed a mechanism to make that happen.

References

Dlugokencky et al., Observational constraints on recent increases in the atmospheric CH4 burden. GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L18803, doi:10.1029/2009GL039780, 2009

Reagan, M. and G. Moridis, Large-scale simulation of methane hydrate dissociation along the West Spitsbergen Margin, GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L23612, doi:10.1029/2009GL041332, 2009

Shakhova et al., Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf, Science 237: 1246-1250, 2010

Shakhova et al., The distribution of methane on the Siberian Arctic shelves: Implications for the marine methane cycle, GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L09601, doi:10.1029/2005GL022751, 2005

Westbrook, G., et al, Escape of methane gas from the seabed along the West Spitsbergen continental margin, GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L15608, doi:10.1029/2009GL039191, 2009

There is an interesting letter in Nature Geoscience this month on what climate changes we have actually already committed ourselves to. The letter, by Mathews and Weaver (sub. reqd.), makes the valid point that there are both climatic and societal inertias to consider.

Their figure neatly demonstrates the different issues:

The upper line is often what is referred to as the ‘climate change commitment’ (for instance Wigley, 2005). This is the warming you get if we keep CO2 (and other GHG and pollutant levels) constant at today’s values. (Technically, the figure shows the case staying at year 2000 values). In such a scenario, the planet still has a radiative imbalance, and the warming will continue until the oceans have warmed sufficiently to equalise the situation – giving an additional 0.3 to 0.8ºC warming over the 21st Century. Thus the conclusion has been that because of climate inertia, further warming is inevitable.

However, constant concentrations of CO2 imply a change in emissions – specifically an immediate cut of around 60 to 70% globally and continued further cuts over time. Matthews and Weaver make the point that this is a little arbitrary and that the true impact of climate inertia would be seen only with emissions cut to zero. That is, if we define the commitment as the consequence only of past emissions, then you should set future emissions to zero before you calculate it. This is a valid point, and the consequence of that is seen in the lower lines in the figure.

CO2 concentrations would start to fall immediately since the ocean and terrestrial biosphere would continue to absorb more carbon than they release as long as the CO2 level in the atmosphere is higher than pre-industrial levels (approximately). And subsequent temperatures (depending slightly on the model you are using) would either be flat or slightly decreasing. With this definition then, there is no climate change commitment because of climate inertia. Instead, the reason for the likely continuation of the warming is that we can’t get to zero emissions any time soon because of societal, economic or technological inertia.

That is an interesting reframing of an issue that comes up all the time in discussions of adaptation and mitigation. This is because it demonstrates that adaptation (over and above what is necessary to reduce vulnerabilities to current climate conditions) is unnecessary if mitigation is dramatic enough.

However, the practical implication of this reframing is small. We are clearly not going to get to zero emissions any time soon, and even the 60-70% cuts required to stabilise concentrations initially seem a long way off. Thus as a practical matter, it doesn’t really matter whether the inertia is climatic or societal or technological or economic because the globe will continue to warm under all realistic scenarios (what we do have a possible control over is the magnitude of that warming). Thus further adaptation measures will still be needed.

Guest commentary from Ben Santer

Part 2 of a series discussing the recent Guardian articles

A recent story by Fred Pearce in the February 9th online edition of the Guardian (“Victory for openness as IPCC climate scientist opens up lab doors”) covers some of the more publicized aspects of the last 14 years of my scientific career. I am glad that Mr. Pearce’s account illuminates some of the non-scientific difficulties I have faced. However, his account also repeats unfounded allegations that I engaged in dubious professional conduct. In a number of instances, Mr Pearce provides links to these allegations, but does not provide a balanced account of the rebuttals to them. Nor does he give links to locations where these rebuttals can be found. I am taking this opportunity to correct Mr. Pearce’s omissions, to reply to the key allegations, and to supply links to more detailed responses.

Another concern relates to Mr. Pearce’s discussion of the “openness” issue mentioned in the title and sub-title of his story. A naïve reader of Mr. Pearce’s article might infer from the sub-title (“Ben Santer had a change of heart about data transparency…”) that my scientific research was not conducted in an open and transparent manner until I experienced “a change of heart”.

This inference would be completely incorrect. As I discuss below, my research into the nature and causes of climate change has always been performed in an open, transparent, and collegial manner. Virtually all of the scientific papers I have published over the course of my career involve multi-institutional teams of scientists with expertise in climate modeling, the development of observational datasets, and climate model evaluation. The model and observational data used in my research is not proprietary – it is freely available to researchers anywhere in the world.

The 1995 IPCC Report: The “scientific cleansing” allegation

Mr. Pearce begins by repeating some of the allegations of misconduct that arose after publication (in 1996) of the Second Assessment Report (SAR) of the Intergovernmental Panel on Climate Change (IPCC). These allegations targeted Chapter 8 of the SAR, which dealt with the “Detection of Climate Change, and Attribution of Causes”. The IPCC SAR reached the historic finding that “The balance of evidence suggests a discernible human influence on global climate”. Information presented in Chapter 8 provided substantial support for this finding.

I served as the Convening Lead Author (CLA) of Chapter 8. There were three principal criticisms of my conduct as CLA. All three allegations are baseless. They have been refuted on many occasions, and in many different fora. All three allegations make an appearance in Mr. Pearce’s story, but there are no links to the detailed responses to these claims.

The first allegation was that I had engaged in “scientific cleansing”. This allegation originated with the Global Climate Coalition (GCC) – a group of businesses “opposing immediate action to reduce greenhouse gas emissions”.

In May 1996, a document entitled “The IPCC: Institutionalized ‘Scientific Cleansing’?” was widely circulated to the press and politicians. In this document, the Global Climate Coalition claimed that after a key Plenary Meeting of the IPCC in Madrid in November 1995, all scientific uncertainties had been purged from Chapter 8. The GCC’s “scientific cleansing” allegation was soon repeated in an article in Energy Daily (May 22, 1996) and in an editorial in the Washington Times (May 24, 1996). It was also prominently featured in the World Climate Report, a publication edited by Professor Patrick J. Michaels (June 10, 1996).

This “scientific cleansing” claim is categorically untrue. There was no “scientific cleansing”. Roughly 20% of the published version of Chapter 8 specifically addressed uncertainties in scientific studies of the causes of climate change. In discussing the “scientific cleansing” issue, Mr. Pearce claims that many of the caveats in Chapter 8 “did not make it to the summary for policy-makers”. This is incorrect.

The Summary for Policymakers (SPM) of the IPCC SAR is four-and-a-half pages long. Roughly one page of the SPM discusses results from Chapter 8. The final paragraph of that page deals specifically with uncertainties, and notes that:

“Our ability to quantify the human influence on global climate is currently limited because the expected signal is still emerging from the noise of natural variability, and because there are uncertainties in key factors. These include the magnitude and patterns of long term natural variability and the time-evolving pattern of forcing by, and response to, changes in concentrations of greenhouse gases and aerosols, and land surface changes”.

Contrary to Mr. Pearce’s assertion, important caveats did “make it to the summary for policy-makers”. And the “discernible human influence” conclusion of both Chapter 8 and the Summary for Policymakers has been substantiated by many subsequent national and international assessments of climate science.

There were several reasons why Chapter 8 was a target for unfounded “scientific cleansing” allegations. First, the Global Climate Coalitions’s “scientific cleansing” charges were released to the media in May 1996. At that time, Cambridge University Press had not yet published the IPCC Second Assessment Report in the United States. Because of this delay in the Report’s U.S. publication, many U.S. commentators on the “scientific cleansing” claims had not even read Chapter 8 – they only had access to the GCC’s skewed account of the changes made to Chapter 8. Had the Second Assessment Report been readily available in the U.S. in May 1996, it would have been easy for interested parties to verify that Chapter 8 incorporated a fair and balanced discussion of scientific uncertainties.

Second, the “pre-Madrid” version of Chapter 8 was the only chapter in the IPCC Working Group I Second Assessment Report to have both an “Executive Summary” and a “Concluding Summary”. As discussed in the next section, this anomaly was partly due to the fact that the Lead Author team for Chapter 8 was not finalized until April 1994 – months after all other chapters had started work. Because of this delay in getting out of the starting blocks, the Chapter 8 Lead Author team was more concerned with completing the initial drafts of our chapter than with the question of whether all chapters in the Working Group I Report had exactly the same structure.

The reply of the Chapter 8 Lead Authors to the Energy Daily story of May 22, 1996 pointed out this ‘two summary’ redundancy, and noted that:

“After receiving much criticism of this redundancy in October and November 1995, the Convening Lead Author of Chapter 8 decided to remove the concluding summary. About half of the information in the concluding summary was integrated with material in Section 8.6. It did not disappear completely, as the Global Climate Coalition has implied. The lengthy Executive Summary of Chapter 8 addresses the issue of uncertainties in great detail – as does the underlying Chapter itself.”

The removal of the concluding summary made it simple for the Global Climate Coalition to advance their unjustified “scientific cleansing” allegations. They could claim ‘This statement has been deleted’, without mentioning that the scientific issue addressed in the deleted statement was covered elsewhere in the chapter.

This was my first close encounter of the absurd kind.

The 1995 IPCC Report: The “political tampering/corruption of peer-review” allegation

The second allegation is that I was responsible for “political tampering”. I like to call this “the tail wags the dog” allegation. The “tail” here is the summary of the Chapter 8 results in the IPCC Summary for Policymakers, and the “dog” is the detailed underlying text of Chapter 8.

In November 1995, 177 government delegates from 96 countries spent three days in Madrid. Their job was to “approve” each word of the four-and-a-half page Summary for Policymakers of the IPCC’s Working Group I Report. This was the report that dealt with the physical science of climate change. The delegates also had the task of “accepting” the 11 underlying science chapters on which the Summary for Policymakers was based. “Acceptance” of the 11 chapters did not require government approval of each word in each chapter.

This was not a meeting of politicians only. A number of the government delegates were climate scientists. Twenty-eight of the Lead Authors of the IPCC Working Group I Report – myself included – were also prominent participants in Madrid. We were there to ensure that the politics did not get ahead of the science, and that the tail did not wag the dog.

Non-governmental organizations – such as the Global Climate Coalition – were also active participants in the Madrid meeting. NGOs had no say in the formal process of approving the Summary for Policymakers. They were, however, allowed to make comments on the SPM and the underlying 11 science chapters during the first day of the Plenary Meeting (November 27, 1996). The Global Climate Coalition dominated the initial plenary discussions.

Most of the plenary discussions at Madrid focused on the portrayal of Chapter 8’s findings in the Summary for Policymakers. Discussions were often difficult and contentious. We wrestled with the exact wording of the “balance of evidence” statement mentioned above. The delegations from Saudi Arabia and Kuwait argued for a very weak statement, or for no statement at all. Delegates from many other countries countered that there was strong scientific evidence of pronounced a human effect on climate, and that the bottom-line statement from Chapter 8 should reflect this.

Given the intense interest in Chapter 8, Sir John Houghton (one of the two Co-Chairs of IPCC Working Group I) established an ad hoc group on November 27, 1996. I was a member of this group. Our charge was to review those parts of the draft Summary for Policymakers that dealt with climate change detection and attribution issues. The group was placed under the Chairmanship of Dr. Martin Manning of New Zealand, and included delegates from the U.S., the U.K., Canada, Kenya, the Netherlands, and New Zealand. Sir John Houghton also invited delegates from Saudi Arabia and Kuwait to participate in this ad hoc group. Unfortunately, they did not accept this invitation.

The ad hoc group considered more than just the portions of the Summary for Policymakers that were relevant to Chapter 8. The Dutch delegation asked for a detailed discussion of Chapter 8 itself, and of the full scientific evidence contained in it. This discussion took place on November 28, 1996.

On November 29, 1996, I reported back to the Plenary on the deliberations of the ad hoc group. The Saudi Arabian and Kuwaiti delegations – who had not attended any of the discussions of the ad hoc group, and had no first-hand knowledge of what had been discussed by the group – continued to express serious reservations about the scientific basis for the detection and attribution statements in the Summary for Policymakers.

On the final evening of the Madrid Plenary Meeting, debate focused on finding the right word to describe the human effect on global climate. There was broad agreement among the government delegates that – based on the scientific evidence presented in Chapter 8 – some form of qualifying word was necessary. Was the human influence “measurable”? Could it be best described as “appreciable”, “detectable”, or “substantial”? Each of these suggested words had proponents and opponents. How would each word translate into different languages? Would the meaning be the same as in English?

After hours of often rancorous debate, Bert Bolin (who was then the Chairman of the IPCC) finally found the elusive solution. Professor Bolin suggested that the human effect on climate should be described as “discernible”.

Mr. Pearce – who was not present at the Madrid Plenary Meeting – argues that the discussion of human effects on climate in the IPCC Summary for Policymakers “went beyond what was said in the chapter from which the summary was supposedly drawn”. In other words, he suggests that the tail wagged the dog. This is not true. The “pre-Madrid” bottom-line statement from Chapter 8 was “Taken together, these results point towards a human influence on climate”. As I’ve noted above, the final statement agreed upon in Madrid was “The balance of evidence suggests a discernible human influence on global climate”.

Is “suggests” stronger than “points towards”? I doubt it. Is “The balance of evidence” a more confident phrase than “Taken together”? I don’t think so.

The primary difference between the pre- and post-Madrid statements is that the latter includes the word “discernible”. In my American Heritage College Dictionary, “discernible” is defined as “perceptible, as by vision or the intellect”. In Merriam-Webster’s Online Dictionary, one of the three meanings of the verb “discern” is “to recognize or identify as separate and distinct”. Was the use of “discernible” justified?

The answer is clearly “yes”. Chapter 8 of the IPCC’s Second Assessment Report relied heavily on the evidence from a number of different “fingerprint” studies. This type of research uses rigorous statistical methods to compare observed patterns of climate change with results from climate model simulations. The basic concept of fingerprinting is that each different influence on climate – such as purely natural changes in the Sun’s energy output, or human-caused changes in atmospheric levels of greenhouse gases – has a unique signature in climate records. This uniqueness becomes more apparent if one looks beyond changes averaged over the entire globe, and instead exploits the much greater information content available in complex, time-varying patterns of climate change.

Fingerprinting has proved to be an invaluable tool for untangling the complex cause-and-effect relationships in the climate system. The IPCC’s Second Assessment Report in 1995 was able to draw on fingerprint studies from a half-dozen different research groups. Each of these groups had independently shown that they could indeed perceive a fingerprint of human influence in observed temperature records. The signal was beginning to rise out of the noise, and was (using Merriam-Webster’s definition of “discern”) “separate and distinct” from purely natural variations in climate.

Based on these fingerprint results, and based on the other scientific evidence available to us in November 1995, use of the word “discernible” was entirely justified. Its use is certainly justified based on the scientific information available to us in 2010. The “discernible human influence” phrase was approved by all of the 177 delegates from 96 countries present at the Plenary Meeting – even by the Saudi and Kuwaiti delegations. None of the 28 IPCC Lead Authors in attendance at Madrid balked at this phrase, or questioned our finding that “the balance of evidence suggests a discernible human influence on global climate”. The latter statement was cautious and responsible, and entirely consistent with the state of the science. The much more difficult job of trying to quantify the size of human influences on climate would be left to subsequent IPCC assessments.

Mr. Pearce’s remarks suggest that there is some substance to the “political tampering” allegation – that I was somehow coerced to change Chapter 8 in order to “reflect the wording of the political summary”. This is untrue. There was no political distortion of the science. If Mr. Pearce had been present at the Madrid Plenary Meeting, he would have seen how vigorously (and successfully) scientists resisted efforts on the part of a small number of delegates to skew and spin some of the information in the Summary for Policymakers.

The key point here is that the SPM was not a “political summary” – it was an accurate reflection of the science. Had it been otherwise, I would not have agreed to put my name on the Report.

A reader of Mr. Pearce’s article might also gain the mistaken impression that the changes to Chapter 8 were only made in response to comments made by government delegates during the Madrid Plenary Meeting. That is not true. As I’ve mentioned above, changes were also made to address government comments made during the meeting of the ad hoc group formed to discuss Chapter 8.

Furthermore, when I first arrived in Madrid on November 26, 1995, I was handed a stack of government and NGO comments on Chapter 8 that I had not seen previously. I had the responsibility of responding to these comments.

One reason for the delay in receiving comments was that the IPCC had encountered difficulties in finding a Convening Lead Author (CLA) for Chapter 8. To my knowledge, the CLA job had been turned down by at least two other scientists before I received the job offer. The unfortunate consequence of this delay was that, at the time of the Madrid Plenary Meeting, Chapter 8 was less mature and polished than other chapters of the IPCC Working Group I Report. Hence the belated review comments.

The bottom line in this story is that the post-Madrid revisions to Chapter 8 were made for scientific, not political reasons. They were made by me, not by IPCC officials. The changes were in full accord with IPCC rules and procedures (pdf). Mr. Pearce repeats accusations by Fred Seitz that the changes to Chapter 8 were illegal and unauthorized, and that I was guilty of “corruption of the peer-review process”. These allegations are false, as the IPCC has clearly pointed out.

The 1995 IPCC Report: The “research irregularities” allegation

The third major front in the attack on Chapter 8 focused on my personal research. It was a two-pronged attack. First, Professor S. Fred Singer claimed that the IPCC’s “discernible human influence” conclusion was entirely based on two of my own (multi-authored) research papers. Next, Professor Patrick Michaels argued that one of these two papers was seriously flawed, and that irregularities had occurred in the paper’s publication process. Both charges were untrue.

On July 25, 1996, I addressed the first of these allegations in an email to the Lead Authors of the 1995 IPCC Report:

“Chapter 8 references more than 130 scientific papers – not just two. Its bottom-line conclusion that “the balance of evidence suggests a discernible human influence on global climate” is not solely based on the two Santer et al. papers that Singer alludes to. This conclusion derives from many other published studies on the comparison of modelled and observed patterns of temperature change – for example, papers by Karoly et al. (1994), Mitchell et al. (1995), Hegerl et al. (1995), Karl et al. (1995), Hasselmann et al. (1995), Hansen et al. (1995) and Ramaswamy et al. (1996). It is supported by many studies of global-mean temperature changes, by our physical understanding of the climate system, by our knowledge of human-induced changes in the chemical composition of the atmosphere, by information from paleoclimatic studies, and by a wide range of supporting information (sea-level rise, retreat of glaciers, etc.). To allege, as Singer does, that “Chapter 8 is mainly based on two research papers” is just plain wrong”.

In the second prong of the attack, Professor Michaels claimed that a paper my colleagues and I had published in Nature in 1996 had been selective in its use of observational data, and that our finding of a human fingerprint in atmospheric temperature data was not valid if a longer observational record was used. Further, he argued that Nature had been “toyed with” (presumably by me), and coerced into publishing the 1996 Santer et al. Nature paper one week prior to a key United Nations meeting in Geneva.

My colleagues and I immediately addressed the scientific criticism of our Nature paper by Michaels and his colleague Chip Knappenberger. We demonstrated that this criticism was simply wrong. Use of a longer record of atmospheric temperature change strengthened rather than weakened the evidence for a human fingerprint. We published this work in Nature in December 1996. Unfortunately, Mr. Pearce does not provide a link to this publication.

Since 1996, studies by a number of scientists around the world have substantiated the findings of our 1996 Nature paper. Such work has consistently shown clear evidence of a human fingerprint in atmospheric temperature records.

Disappointingly, Professor Michaels persists in repeating his criticism of our paper, without mentioning our published rebuttal or the large body of subsequently published evidence refuting his claims. Michaels’ charge that Nature had been “toyed with” was complete nonsense. As described below, however, this was not the last time I would be falsely accused of having the extraordinary power to force scientific journals to do my bidding.

A Climatology Conspiracy? More “peer-review abuse” accusations

Mr. Pearce also investigates a more recent issue. He implies that I abused the normal peer-review system, and exerted pressure on the editor of the International Journal of Climatology to delay publication of the print version of a paper by Professor David Douglass and colleagues. This is not true.

The Douglass et al. paper was published in December 2007 in the online edition of the International Journal of Climatology. The “et al.” included the same Professor S. Fred Singer who had previously accused me of “scientific cleansing”. It also included Professor John Christy, the primary developer of a satellite-based temperature record which suggests that there has been minimal warming of Earth’s lower atmosphere since 1979. Three alternate versions of the satellite temperature record, produced by different teams of researchers using the same raw satellite measurements, all indicate substantially more warming of the Earth’s atmosphere.

The focus of the Douglass et al. paper was on post-1979 temperature changes in the tropics. The authors devised what they called a “robust statistical test” to compare computer model results with observations. The test was seriously flawed (see Appendix A in Open Letter to the Climate Science Community: Response to A “Climatology Conspiracy?”). When it was applied to the model and observational temperature datasets, the test showed (quite incorrectly) that the model results were significantly different from observations.

As I have noted elsewhere, the Douglass et al. paper immediately attracted considerable media and political attention. One of the paper’s authors claimed that it represented an “inconvenient truth”, and proved that “Nature, not humans, rules the climate”. These statements were absurd. No single study can overturn the very large body of scientific evidence supporting “discernible human influence” findings. Nor does any individual study provide the sole underpinning for the conclusion that human activities are influencing global climate.

Given the extraordinary claims that were being made on the basis of this incorrect paper, my colleagues and I decided that a response was necessary. Although the errors in Douglass et al. were easy to identify, it required a substantial amount of new and original work to repeat the statistical analysis properly.

Our work went far beyond what Douglass et al. had done. We looked at the sensitivity of model-versus-data comparisons to the choice of statistical test, to the test assumptions, to the number of years of record used in the tests, and to errors in the computer model estimates of year-to-year temperature variability. We also examined how the statistical test devised by Douglass et al. performed under controlled conditions, using random data with known statistical properties. From their paper, there is no evidence that Douglass et al. considered any of these important issues before making their highly-publicized claims.

Our analysis clearly showed that tropical temperature changes in observations and climate model simulations were not fundamentally inconsistent – contrary to the claim of Douglass and colleagues. Our research was published on October 10, 2008, in the online edition of the International Journal of Climatology. On November 15, 2008, the Douglass et al. and Santer et al. papers appeared in the same print version of the International Journal of Climatology.

In December 2009, shortly after the public release of the stolen emails from the University of East Anglia’s Climatic Research Unit, Professors David Douglass and John Christy accused me of leading a conspiracy to delay publication of the print version of the Douglass et al. paper. This accusation was based on a selective analysis of the stolen emails. It is false.

In Mr. Pearce’s account of this issue, he states that “There is no doubt the (sic) Santer and his colleagues sought to use the power they held to the utmost…” So what are the facts of this matter? What is the “power” Fred Pearce is referring to?

• Fact 1: The only “power” that I had was the power to choose which scientific journal to submit our paper to. I chose the International Journal of Climatology. I did this because the International Journal of Climatology had published (in their online edition) the seriously flawed Douglass et al. paper. I wanted to give the journal the opportunity to set the scientific record straight.
• Fact 2: I had never previously submitted a paper to the International Journal of Climatology. I had never met the editor of the journal (Professor Glenn McGregor). I did not have any correspondence or professional interaction with the editor prior to 2008.
• Fact 3: Prior to submitting our paper, I wrote an email to Dr. Tim Osborn on January 10, 2008. Tim Osborn was on the editorial board of the International Journal of Climatology. I told Dr. Osborn that, before deciding whether we would submit our paper to the International Journal of Climatology, I wanted to have some assurance that our paper would “be regarded as an independent contribution, not as a comment on Douglass et al.” This request was entirely reasonable in view of the substantial amount of new work that we had done. I have described this new work above.
• Fact 4: I did not want to submit our paper to the International Journal of Climatology if there was a possibility that our submission would be regarded as a mere “comment” on Douglass et al. Under this scenario, Douglass et al. would have received the last word. Given the extraordinary claims they had made, I thought it unlikely that their “last word” would have acknowledged the serious statistical error in their original paper. As subsequent events showed, I was right to be concerned – they have not admitted any error in their work.
• Fact 5: As I clearly stated in my email of January 10 to Dr. Tim Osborn, if the International Journal of Climatology agreed to classify our paper as an independent contribution, “Douglass et al. should have the opportunity to respond to our contribution, and we should be given the chance to reply. Any response and reply should be published side-by-side…”
• Fact 6: The decision to hold back the print version of the Douglass et al. paper was not mine. It was the editor’s decision. I had no “power” over the publishing decisions of the International Journal of Climatology.

This whole episode should be filed under the category “No good deed goes unpunished”. My colleagues and I were simply trying to set the scientific record straight. There was no conspiracy to subvert the peer-review process. Unfortunately, conspiracy theories are easy to disseminate. Many are willing to accept these theories at face value. The distribution of facts on complex scientific issues is a slower, more difficult process.

Climate Auditing – Close Encounters with Mr. Steven McIntyre

Ten days after the online publication of our International Journal of Climatology paper, Mr. Steven McIntyre, who runs the “ClimateAudit” blog, requested all of the climate model data we had used in our research. I replied that Mr. McIntyre was welcome to “audit” our calculations, and that all of the primary model data we had employed were archived at Lawrence Livermore National Laboratory and freely available to any researcher. Over 3,400 scientists around the world currently analyze climate model output from this open database.

My response was insufficient for Mr. McIntyre. He submitted two Freedom of Information Act (FOIA) requests for climate model data – not for the freely available raw data, but for the results from intermediate calculations I had performed with the raw data. One FOIA request also asked for two years of my email correspondence related to these climate model data sets.

I had performed these intermediate calculations in order derive weighted-average temperature changes for different layers of the atmosphere. This is standard practice. It is necessary since model temperature data are available at specific heights in the atmosphere, whereas satellite temperature measurements represent an average over a deep layer of the atmosphere. The weighted averages calculated from the climate model data can be directly compared with actual satellite data. The method used for making such intermediate calculations is not a secret. It is published in several different scientific journals.

Unlike Mr. McIntyre, David Douglass and his colleagues (in their International Journal of Climatology paper) had used the freely available raw model data. With these raw datasets, Douglass et al. made intermediate calculations similar to the calculations we had performed. The results of their intermediate calculations were similar to our own intermediate results. The differences between what Douglass and colleagues had done and what my colleagues and I had done was not in the intermediate calculations – it was in the statistical tests each group had used to compare climate models with observations.

The punch-line of this story is that Mr. McIntyre’s Freedom of Information Act requests were completely unnecessary. In my opinion, they were frivolous. Mr. McIntyre already had access to all of the information necessary to check our calculations and our findings.

When I invited Mr. McIntyre to “audit” our entire study, including the intermediate calculations, and told him that all the data necessary to perform such an “audit” were freely available, he expressed moral outrage on his blog. I began to receive threatening emails. Complaints about my “stonewalling” behavior were sent to my superiors at Lawrence Livermore National Laboratory and at the U.S. Department of Energy.

A little over a month after receiving Mr. McIntyre’s Freedom of Information Act requests, I decided to release all of the intermediate calculations I had performed for our International Journal of Climatology paper. I made these datasets available to the entire scientific community. I did this because I wanted to continue with my scientific research. I did not want to spend all of my available time and energy responding to harassment incited by Mr. McIntyre’s blog.

Mr. Pearce does not mention that Mr. McIntyre had no need to file Freedom of Information Act requests, since Mr. McIntyre already had access to all of the raw climate model data we had used in our study (and to the methods we had used for performing intermediate calculations). Nor does Mr. Pearce mention the curious asymmetry in Mr. McIntyre’s “auditing”. To my knowledge, Mr. McIntyre – who purports to have considerable statistical expertise – has failed to “audit” the Douglass et al. paper, which contained serious statistical errors.

As the “Climategate” emails clearly show, there is a pattern of behavior here. My encounter with Mr. McIntyre’s use of FOIA requests for “audit” purposes is not an isolated event. In my opinion, Mr. McIntyre’s FOIA requests serve the purpose of initiating fishing expeditions, and are not being used for true scientific discovery.

Mr. McIntyre’s own words do not present a picture of a man engaged in purely dispassionate and objective scientific inquiry:

“But if Santer wants to try this kind of stunt, as I’ve said above, I’ve submitted FOI requests and we’ll see what they turn up. We’ll see what the journal policies require. I’ll also see what DOE and PCDMI administrators have to say. We’ll see if any of Santer’s buddies are obligated to produce the data. We’ll see if Santer ever sent any of the data to his buddies”

(Steven McIntyre; posting on his ClimateAudit blog; Nov. 21, 2008).

My research is subject to rigorous scrutiny. Mr. McIntyre’s blogging is not. He can issue FOIA requests at will. He is the master of his domain – the supreme, unchallenged ruler of the “ClimateAudit” universe. He is not a climate scientist, but he has the power to single-handedly destroy the reputations of exceptional men and women who have devoted their entire careers to the pursuit of climate science. Mr. McIntyre’s unchecked, extraordinary power is the real story of “Climategate”. I hope that someone has the courage to tell this story.

Benjamin D. Santer

John D. and Catherine T. MacArthur Fellow
San Ramon, California
February 22, 2010*

*These remarks reflect the personal opinions of Benjamin D. Santer. They do not reflect the official views of Lawrence Livermore National Laboratory or the U.S. Department of Energy. In preparing this document, I would like to acknowledge the assistance of Tom Wigley, Myles Allen, Kristin Aydt, Graham Cogley, Peter Gleckler, Leo Haimberger, Gabi Hegerl, John Lanzante, Mike MacCracken, Gavin Schmidt, Steve Sherwood, Susan Solomon, Karl Taylor, Simon Tett, and Peter Thorne.

Over the last few weeks or so the UK Guardian (who occasionally reprint our posts) has published a 12-part series about the stolen CRU emails by Fred Pearce that are well below the normal Guardian standards of reporting. We delineate some of the errors and misrepresentations below. While this has to be seen on a backdrop of an almost complete collapse in reporting standards across the UK media on the issue of climate change, it can’t be excused on the basis that the Mail or the Times is just as bad. As a long-time Guardian reader and avid Guardian crossword puzzle solver, I’m extremely unhappy writing this post, but the pathologies of media reporting on this issue have become too big to ignore.

We highlight issues with three of the articles below, which revisit a number of zombie arguments that have been doing the rounds of the sceptic blogs for years. Two follow-up pieces will deal with two further parts of the series. Hopefully some of the more egregious factual errors can be fixed as part of a ‘group experiment‘ in improving the stories, though the larger misconceptions probably can’t be (and readers should feel free to use this information to comment on the articles directly). Why the Guardian is asking for group input after the stories were published instead of before is however a puzzle. Some of the other pieces in this series are fine, which makes the ones that get it so wrong all the more puzzling. The errors consist of mistakes in the basic science, misunderstandings of scientific practice, more out of context quotes and some specific issues that are relatively new. (In the text below, quotes from the articles are in italics).

Part 3: Hockey Sticks

Some of the more egregious confusions and errors were in the third part of the series. In this part, a number of issues that were being discussed among the paleo-community in 1999 were horribly mixed up. For instance, there was a claim that arguments on the zeroth-order draft of the 2001 IPCC report were based on Briffa’s reconstruction showed the 11th century as being almost as warm as the 20th century, while Mann’s graph found little sign of the earlier warming. But this is simply untrue since at the time Briffa’s curve only went back to 1400 AD (not the 11th Century) and the discussions had nothing to do with the medieval warm period, but rather the amount of multi-decadal variability in the three different reconstructions then available. This was corrected in the online edition, but the description of the dispute in the article is still very confused.

That discussion was conflated with a completely separate April 1999 issue based on a disagreement about a perspectives piece in Science (which appeared as Briffa and Osborn, 1999) and which was in any case amicably resolved.

That discussion is then further confused with the discussions about the framing of the SPM text which despite Pearce claiming that ‘the emails reveal how deeply controversial it was at the time, did not get discussed in the emails at all. And while the article claimed that the uncertainty was not discussed in the IPCC report, the discussion in Chapter 2 was actually quite extensive.

Part 5: Chinese weather stations

This piece concerns the response of Phil Jones at CRU to a FOI request for data that had been used in a 1990 paper on the urban heat island (UHI). This now-20 year old paper was an early attempt to try and assess the possible magnitude of the UHI impact on the global temperature records. (Note that this is not the same as thinking that UHI does not exist).

Starting from the headline “Leaked climate change emails scientist ‘hid’ data flaws” on down, the article is full of misrepresentations. To start with, the data in question (and presumably it’s flaws) were not hidden by anyone, but rather had been put on the CRU server in 2007 response to a FOI request. Hardly ‘hidden’. Exactly contrary to the truth of the matter, the article incorrectly asserted that ‘Jones withheld the information requested under freedom of information laws’.

These data assumed a much greater importance later in 2007 when they were used for a completely unsubstantiated claim of ‘fabrication’ and ‘fraud’ against Wei-Chyung Wang (a co-author on the paper) at SUNY Albany by a certain Douglas Keenan. These charges were found by the university to be baseless in 2009 and the matter was dropped. However, the Guardian noted that a couple of the emails mentioned the issue, and that one in particular had Tom Wigley asking Phil Jones about the situation. Curiously enough, Phil Jones’ response was not part of the archive, and Wigley’s current thoughts on the subject (presumably that have been informed by Jones’ answers) were not reported.

Pearce describes this conversation saying that ‘new information brought to light today indicates at least one senior colleague had serious concerns about the affair‘. However, Tom Wigley has subsequently passed on later conversations to me showing very clearly that he did not support Keenan’s allegations of ‘fabrication’ and the implication that he does here are very misleading. Indeed, the statement that ‘Tom Wigley, harboured grave doubts about the cover-up‘ is completely false. There was no ‘cover-up’; the email was written two years after the data had been posted online.

The line in the 1990 paper that has apparently caused the furore is the following:

“The stations were selected on the basis of station history: we chose those with few, if any, changes in instrumentation, location or observation times.”

For fraud to have been proven, it would have been necessary to show that Wang – at the time of the 1990 paper – deliberately misled in the line as it was written. It would not be enough to show that the statement was mistaken because of incomplete histories available to him at that time, nor that some stations had in fact moved. The statement is a declaration of a good faith effort to pick suitable stations. Instead, you would have to demonstrate that Wang was aware of substantial and important moves that
made a material difference and deliberately concealed this fact. And for this there is absolutely no evidence. Keenan’s assumption of fabrication is merely that, an assumption.

Wigley’s ‘grave doubts’ were a suggestion that the key line be rewritten as

“Where possible, stations were chosen on the basis of station histories and/or local knowledge: selected stations have relatively few, if any, changes in instrumentation, location, or observation times”

A change that doesn’t undermine the paper in the slightest, and would hardly be likely to set the blogosphere aflame.

Quite frankly this whole allegation is absurd – why would anyone do this? All the authors involved have written many papers on the problems in the temperature record and on Urban Heat Islands in general, and even in China. Indeed the story here is that information was provided under FOI rules, and that it was not used to constructively examine the science, but rather to provide ammunition for baseless accusations that led to pointless university inquiries into alleged misconduct. That might be a good reason for why FOI requests are now being viewed with suspicion.

Other claims that this ‘may yet result in a significant revision of a scientific paper that is still cited by the UN’s top climate science body‘ . and that ‘what data is available suggests that the findings are fundamentally flawed‘ are simply made up. The findings of the 1990 paper was that UHI was unlikely to be contaminating the global temperature records in any significant way has been upheld by any number of additional studies in the 20 years since it was published. Oceans are not warming because of UHI, spring is not coming earlier because of UHI, and indeed, glaciers are not melting because of UHI (they are of course melting, recent news reports notwithstanding). No evidence of significant UHI contamination was found by Parker (2004, 2006), the record from GISTEMP which applies a different UHI correction than HadCRUT does not differ substantially at the global or regional scale. Other studies by Peterson, Jones, and others all show similar results. Even the more recent analyses of the Chinese stations themselves and even in an environment where urbanisation is happening faster than ever, UHI effects are still small (Jones et al, 2008).

As an aside, Keenan has made a cottage industry of accusing people of fraud whenever someone writes a paper of which he disapproves. He has attempted to get the FBI to investigate Mike Mann, pursued a vendetta against a Queen’s University Belfast researcher, and has harassed a French graduate student with fraud accusations based on completely legitimate choices in data handling. More recently Keenan, who contacted Wigley after having seen the email mentioned in the Pearce story, came to realise that Wigley was not in agreement with his unjustified allegations of ‘fraud’. In response, Keenan replied (in an email dated Jan 10, 2010) that:

.. this has encouraged me to check a few of your publications: some are so incompetent that they seem to be criminally negligent.


Sincerely, Doug

This kind of knee-jerk presumption of misconduct (and criminal misconduct at that) when people disagree with you has no place in the scientific discourse, and serves only to poison scientific debate. Indeed, Jones adds in one of the emails: “I’d be far happier if they would write some papers and act in the normal way. I’d know how to respond to that”. For the Guardian to dignify this kind of behaviour – especially after the charges had been investigated and dismissed – is unconscionable and a public apology should be forthcoming to Jones, Wigley and Wang.

Part 6: Peer review

The discussion of peer review is the most replete with basic misconceptions about the scientific process. Pearce appears to conflate any rejection of a paper or even a negative review for any reason as a prima facie case of mainstream climate scientists … censoring their critics. But in none of the cases highlighted were anyone’s view ‘censored’. To have your opinion published in peer-reviewed literature is not some fundamental right – it is a privilege that depends on your ability to do the analysis and the marshal the logical arguments and data to support your point.

Pearce, surprisingly for someone who has been on a science beat for a long time, states that peer review is the supposed gold standard of scientific merit. This is not the case at all. As we’ve outlined in many articles, peer review is just a first (necessary) step towards scientific acceptance and as the number of badly flawed papers that do appear in the literature attest, it is no guarantee of merit. For it to work of course there need to be some standards that should ideally be met, and this will lead to the rejection of some submissions. Thus automatically equating rejections of bad submissions with squashing of ‘dissent’ is like assuming that anyone who gets an F on a test is being unfairly discriminated against.

Pearce also declares that the mere act of reviewing a paper that is critical of your own work is mired in ‘conflicts of interest that would not be allowed in most professions‘. This is wrong on multiple levels. First of all, peer review of the literature is hardly unique to climate science, and so his claim about improper conflicts of interest is an accusation against the whole of science, not just climatology. Secondly, he confuses the role of the reviewer with that of the editor. Editors often solicit reviews of a critical comment directly from those being criticised, since that is often the easiest way to judge whether the critique is substantive. That is not the same as giving the right of veto to the criticised authors since, of course, it’s the editor’s job to weigh the different reviews from different sources, and use their own judgment as to the merits of the critique. Not asking the original authors for comment can certainly be (and has been) problematic and unfair to them. The problems most often arise – such as in Soon and Baliunas (2003) or McIntyre and McKitrick (2003;2005) when the criticised authors are not involved at all.

In the cases mentioned in this article, there is absolutely no evidence of unfair discrimination. Indeed, in one case of a submission by Lars Kamel, the reasons for rejection are obvious and Pearce appears not to know what the criteria for acceptance even are. He states that “the finding sounded important, but his paper was rejected by Geophysical Research Letters (GRL) that year“. But papers are not accepted or rejected because a finding ’sounds important’, but because that finding is backed up by analysis and logic while acknowledging the prior work on the topic. In this case, the author did not “however, justify that conclusion with any data or analysis“, and so a rejected manuscript would have been very likely, regardless of who the reviewers were. Similarly, the assumption that “some would have recommended publication” purely because it called into question previous work is unsupportable as a general rule. Filling the literature with papers ‘just asking questions’ that ’sound important’ but not demonstrating any actual results is a recipe for wasting everyone’s time with poorly thought out, and even mendacious, critiques of mainstream science from HIV-denial to perpetual motion machines. Papers in the technical literature are not just opinion.

Pearce also assumes (without evidence) that Kamel was discriminated against because Jones “would certainly have been aware of Kamel’s [negative] views about mainstream climate research“. But why should this be assumed? Most scientists (luckily) go through their whole career without wasting their time investigating and cataloguing the cranks in their field. Some climate sceptics get addressed here on RC a fair bit, but it would be a big mistake to think that these people, particularly the more obscure ones, are the subject of water cooler conversations at climate research labs across the world. Indeed, I can find no reference to Kamel on RC at all and I was unaware of his peculiar views until this story emerged. Why Jones should be assumed to omniscient on this topic is unclear.

Pearce quotes McIntyre discussing “CRU’s policies of obstructing critical articles in the peer-reviewed literature” slowing the resolution of unspecified “issues”. This is simply disingenuous – what papers have been obstructed that would have resolved what issues? We are unaware of any such papers, and certainly none from McIntyre. Prior therefore to declaring that “evidence, flawed though it might be, is actively being kept out of the journals” it behoves Pearce to actually find such evidence. Otherwise, the simple non-appearance of these mythical critiques is apparently proof of the corruption of the peer review process.

As an additional example of problematic practice, Pearce highlights a June 2003 email from Keith Briffa, who as an editor ‘emailed fellow tree-ring researcher Edward Cook, a researcher at Lamont-Doherty Earth Observatory in New York, saying: “Confidentially I now need a hard and if required extensive case for rejecting [an unnamed paper] to ­support Dave Stahle’s and really as soon as you can.”‘. However, without context this is meaningless. People often sign reviews and this could well have been a second go around on a particular paper whose first round reviews would have been seen by everyone concerned. Briffa (like many editors) can have a feeling that a paper should be rejected for multiple reasons but would like to have the reasons gone into in some detail, mostly for the benefit of the authors. This is one reason why reviewing bad papers is so much more work than good ones. Quoting this as if it absolutely demonstrated bad faith or misconduct is simply a smear.

Pearce then accuses Cook of some unjustified quid-pro-quo because he wanted to use some of Briffa’s data to assess the practical implications of a new analysis technique, that Pearce interprets as “attacking his own tree-ring work“. However, this too is a misreading. The work in question has subsequently been revised and the authors themselves have said that the current submission is improved over the initial submission. It goes along with the overall point made above, that pure criticism is not particularly useful – it is much better to demonstrate that some technical point actually matters. This is what Cook appears to be asking for help to demonstrate.

The article then moves on to the issue of the 2003 Soon and Baliunas paper in Climate Research. Pearce nowhere acknowledges that it is (and was) widely regarded as a complete failure of the peer review system. Six (very independent minded) editors resigned from the journal because of the publisher’s inaction on tightening up peer review standards and even the publisher himself declared that the paper’s conclusions were not supported by the data or analysis of the authors. Is this not germane?

Pearce suggests that the reaction to the demonstrably low standards at Climate Research involved “improper pressure“. This has no validity whatsoever. The suggestion was made that maybe people should not submit work to the journal or cite work that appeared there. But how can a suggestion made among colleagues and not transmitted more widely be ‘pressure’ of any sort? People have their impressions about journals determined by many factors, and if they are seen to be publishing bad papers, that will be noted. Compare the reputations of Science and E&E for instance. Which would you rather be published in if you had a good paper?

The one email that Pearce declares “means what it seems to mean” refers to the declaration (along with exclamation point) that Jones would “redefine peer-review!” rather than include two flawed papers in the AR4 report. But it should be obvious that no-one gets to redefine what ‘peer reviewed’ means, and the exclamation point underlines the fact that this was hyperbole. The two papers referred to (McKitrick and Michaels, 2004; Kalnay and Cai, 2003)) were indeed discussed in Chapter 2 of AR4 as the contributing lead author of that chapter Trenberth rightly pointed out. As an aside neither have stood the test the time.

The problem with lapses in peer review (which will inevitably occur) is that they are sometimes systematic, indicating a more institutional problem instead of simply an unfortunate combination of poor reviewers and a busy editor. This appeared to occur at Geophysical Research Letters over the period 2005-2006. There was a string of bad papers published – ones that did not properly support their conclusions and made basic errors in the science. For instance, Douglass and Knox (2005), Douglass, Patel and Knox (2005), Douglass, Pearson and Singer (2004), Douglass, Pearson, Singer, Knappenberger, and Michaels (2004), and Loáiciga (2006).

Science is indeed a ’self-correcting’ process, but someone has to do that correcting, and scientists do get frustrated when they have to spend weeks dealing with the aftermath of bad papers in the media and putting together the comments that almost every single one of these papers generated. (For amusement and for an example of the lack of standards being talked about, look at the response of Bjornsson et al to the Douglass, Patel and Knox paper).

Are scientists supposed not to notice these patterns? Or never discuss them among colleagues? The implication that the mere discussion of the situation is somehow a corruption of the peer review process is completely unjustified. Peer review only holds the status it does because scientists are on guard against failures in the system and try to correct them when they occur.

Update: Coincidentally, David Adams on the Guardian makes many of the same points as we do.

In two follow-up pieces we will host a letter from Ben Santer on Part 7 and on the skewed reporting of the ‘Yamal‘ issue in Part 9.

Who says that the climate debate is not evolving? According to the daily newspaper the Guardian, a new application (‘app‘) has been written for iPhones that provides a list of climate dissidents’ arguments, and counter arguments based on more legitimate scientific substance. The app is developed by John Cook from ‘Skeptical Science‘. It’s apparently enough to have the climate dissidents up in arms – meaning that it’s likely to have some effect? Some dissidents are now thinking of writing their own app.

Here on RC, we have developed a wiki, to which I also would like to bring the reader’s attention. Furthermore, I want to remind the readers about other useful web sites, listed at our blog roll.

It won’t have escaped many of our readers’ notice that there has been what can only be described as a media frenzy (mostly in the UK) with regards to climate change in recent weeks. The coverage has contained more bad reporting, misrepresentation and confusion on the subject than we have seen in such a short time anywhere. While the UK newspaper scene is uniquely competitive (especially compared to the US with over half a dozen national dailies selling in the same market), and historically there have been equally frenzied bouts of mis-reporting in the past on topics as diverse as pit bulls, vaccines and child abductions, there is something new in this mess that is worth discussing. And that has been a huge shift in the Overton window for climate change.

In any public discussion there are bounds which people who want to be thought of as having respectable ideas tend to stay between. This is most easily seen in health care debates. In the US, promotion of a National Health Service as in the UK or a single-payer system as in Canada is so far outside the bounds of normal health care politics, that these options are only ever brought up by ‘cranks’ (sigh). Meanwhile in the UK, discussions of health care delivery solutions outside of the NHS framework are never heard in the mainstream media. This limit on scope of the public debate has been called the Overton window.

The window does not have to remain static. Pressure groups and politicians can try and shift the bounds deliberately, or sometimes they are shifted by events. That seems to have been the case in the climate discussion. Prior to the email hack at CRU there had long been a pretty widespread avoidance of ‘global warming is a hoax’ proponents in serious discussions on the subject. The sceptics that were interviewed tended to be the slightly more sensible kind – people who did actually realise that CO2 was a greenhouse gas for instance. But the GW hoaxers were generally derided, or used as punchlines for jokes. This is not because they didn’t exist and weren’t continually making baseless accusations against scientists (they did and they were), but rather that their claims were self-evidently ridiculous and therefore not worth airing.

However, since the emails were released, and despite the fact that there is no evidence within them to support any of these claims of fraud and fabrication, the UK media has opened itself so wide to the spectrum of thought on climate that the GW hoaxers have now suddenly find themselves well within the mainstream. Nothing has changed the self-evidently ridiculousness of their arguments, but their presence at the media table has meant that the more reasonable critics seem far more centrist than they did a few months ago.

A few examples: Monckton being quoted as a ‘prominent climate sceptic’ on the front page of the New York Times this week (Wow!); The Guardian digging up baseless fraud accusations against a scientist at SUNY that had already been investigated and dismissed; The Sunday Times ignoring experts telling them the IPCC was right in favor of the anti-IPCC meme of the day; The Daily Mail making up quotes that fit their GW hoaxer narrative; The Daily Express breathlessly proclaiming the whole thing a ‘climate con’; The Sunday Times (again) dredging up unfounded accusations of corruption in the surface temperature data sets. All of these stories are based on the worst kind of oft-rebunked nonsense and they serve to make the more subtle kind of scepticism pushed by Lomborg et al seem almost erudite.

Perhaps this is driven by editors demanding that reporters come up with something new (to them) that fits into an anti-climate science theme that they are attempting to stoke. Or perhaps it is driven by the journalists desperate to maintain their scoop by pretending to their editors that this nonsense hasn’t been debunked a hundred times already? Who knows? All of these bad decisions made easier when all of the actually sensible people, or people who know anything about the subject at all, are being assailed on all sides, and aren’t necessarily keen to find the time to explain, once again, that yes, the world is warming.

So far, so stupid. But even more concerning is the reaction from outside the UK media bubble. Two relatively prominent and respected US commentators – Curtis Brainard at CJR and Tom Yulsman in Colorado – have both bemoaned the fact that the US media (unusually perhaps) has not followed pell-mell into the fact-free abyss of their UK counterparts. Their point apparently seems to be that since much news print is being devoted to a story somewhere, then that story must be worth following. Indeed, since the substance to any particularly story is apparently proportional to the coverage, by not following the UK bandwagon, US journalists are missing a big story. Yulsman blames the lack of environmental beat reporters for lack of coverage in the US, but since most of the damage and bad reporting on this is from clueless and partisan news desk reporters in the UK, I actually expect that it is the environmental beat reporters prior experience with the forces of disinformation that prevents the contagion crossing the pond. To be sure, reporters should be able and willing (and encouraged) to write stories about anything to do with climate science and its institutions – but that kind of reporting is something very different from regurgitating disinformation, or repeating baseless accusations as fact.

So what is likely to happen now? As the various panels and reports on the CRU affair conclude, it is highly likely (almost certain in fact) that no-one will conclude that there has been any fraud, fabrication or scientific misconduct (since there hasn’t been). Eventually, people will realise (again) that the GW hoaxers are indeed cranks, and the mainstream window on their rants will close. In the meantime, huge amounts of misinformation, sprinkled liberally with plenty of disinformation, will be spread and public understanding on the issue will likely decline. As the history of the topic has shown, public attention to climate change comes and goes and this is likely to be seen as the latest bump on that ride.

Eppure si riscalda.

Yesterday, the Daily Mail of the UK published a predictably inaccurate article entitled “Climategate U-turn as scientist at centre of row admits: There has been no global warming since 1995″.

The title itself is a distortion of what Jones actually said in an interview with the BBC. What Jones actually said is that, while the globe has nominally warmed since 1995, it is difficult to establish the statistical significance of that warming given the short nature of the time interval (1995-present) involved. The warming trend consequently doesn’t quite achieve statistical significance. But it is extremely difficult to establish a statistically significant trend over a time interval as short as 15 years–a point we have made countless times at RealClimate. It is also worth noting that the CRU record indicates slightly less warming than other global temperature estimates such as the GISS record.

The article also incorrectly equates instrumental surface temperature data that Jones and CRU have assembled to estimate the modern surface temperature trends with paleoclimate data used to estimate temperatures in past centuries, falsely asserting that the former “has been used to produce the ‘hockey stick graph’”.

Finally, the article intentionally distorts comments that Jones made about the so-called “Medieval Warm Period”. Jones stated in his BBC interview that “There is much debate over whether the Medieval Warm Period was global in extent or not. The MWP is most clearly expressed in parts of North America, the North Atlantic and Europe and parts of Asia” and that “For it to be global in extent, the MWP would need to be seen clearly in more records from the tropical regions and the Southern hemisphere. There are very few palaeoclimatic records for these latter two regions.”

These are statements with which we entirely agree, and they are moreover fully consistent with the conclusions of the most recent IPCC report, and the numerous peer-reviewed publications on this issue since. Those conclusions are that recent Northern Hemisphere warming is likely unprecedented in at least a millennium (at least 1300 years, in fact), and that evidence in the Southern Hemisphere is currently too sparse for confident conclusions. Mann et al in fact drew those same conclusions in their most recent work on this problem (PNAS, 2008).

Unfortunately, these kinds of distortions are all too common in the press nowadays and so we must all be prepared to respond to those journalists and editors who confuse the public with such inaccuracies.

Update 2/16/10. Phil Jones has confirmed to us that our interpretations of his comments in the BBC interview are indeed the correct ones, and that he agrees with the statements in our piece above. He and his CRU colleagues have also put up an response to some of the false allegations in a previous piece in the UK Guardian. We’ll report further such developments as they happen.

Currently, a few errors –and supposed errors– in the last IPCC report (“AR4″) are making the media rounds – together with a lot of distortion and professional spin by parties interested in discrediting climate science.  Time for us to sort the wheat from the chaff: which of these putative errors are real, and which not? And what does it all mean, for the IPCC in particular, and for climate science more broadly?

Let’s start with a few basic facts about the IPCC.  The IPCC is not, as many people seem to think, a large organization. In fact, it has only 10 full-time staff in its secretariat at the World Meteorological Organization in Geneva, plus a few staff in four technical support units that help the chairs of the three IPCC working groups and the national greenhouse gas inventories group. The actual work of the IPCC is done by unpaid volunteers – thousands of scientists at universities and research institutes around the world who contribute as authors or reviewers to the completion of the IPCC reports. A large fraction of the relevant scientific community is thus involved in the effort.  The three working groups are:

Working Group 1 (WG1), which deals with the physical climate science basis, as assessed by the climatologists, including several of the Realclimate authors.

Working Group 2 (WG2), which deals with impacts of climate change on society and ecosystems, as assessed by social scientists, ecologists, etc.

Working Group 3 (WG3) , which deals with mitigation options for limiting global warming, as assessed by energy experts, economists, etc.

Assessment reports are published every six or seven years and writing them takes about three years. Each working group publishes one of the three volumes of each assessment. The focus of the recent allegations is the Fourth Assessment Report (AR4), which was published in 2007.  Its three volumes are almost a thousand pages each, in small print. They were written by over 450 lead authors and 800 contributing authors; most were not previous IPCC authors. There are three stages of review involving more than 2,500 expert reviewers who collectively submitted 90,000 review comments on the drafts. These, together with the authors’ responses to them, are all in the public record (see here and here for WG1 and WG2 respectively).

Errors in the IPCC Fourth Assessment Report (AR4)

As far as we’re aware, so far only one–or at most two–legitimate errors have been found in the AR4:

Himalayan glaciers: In a regional chapter on Asia in Volume 2, written by authors from the region, it was erroneously stated that 80% of Himalayan glacier area would very likely be gone by 2035. This is of course not the proper IPCC projection of future glacier decline, which is found in Volume 1 of the report. There we find a 45-page, perfectly valid chapter on glaciers, snow and ice (Chapter 4), with the authors including leading glacier experts (such as our colleague Georg Kaser from Austria, who first discovered the Himalaya error in the WG2 report).  There are also several pages on future glacier decline in Chapter 10 (“Global Climate Projections”), where the proper projections are used e.g. to estimate future sea level rise. So the problem here is not that the IPCC’s glacier experts made an incorrect prediction. The problem is that a WG2 chapter, instead of relying on the proper IPCC projections from their WG1 colleagues, cited an unreliable outside source in one place. Fixing this error involves deleting two sentences on page 493 of the WG2 report.

Sea level in the Netherlands: The WG2 report states that “The Netherlands is an example of a country highly susceptible to both sea-level rise and river flooding because 55% of its territory is below sea level”. This sentence was provided by a Dutch government agency – the Netherlands Environmental Assessment Agency, which has now published a correction stating that the sentence should have read “55 per cent of the Netherlands is at risk of flooding; 26 per cent of the country is below sea level, and 29 per cent is susceptible to river flooding”. It surely will go down as one of the more ironic episodes in its history when the Dutch parliament last Monday derided the IPCC, in a heated debate, for printing information provided by … the Dutch government. In addition, the IPCC notes that there are several definitions of the area below sea level. The Dutch Ministry of Transport uses the figure 60% (below high water level during storms), while others use 30% (below mean sea level). Needless to say, the actual number mentioned in the report has no bearing on any IPCC conclusions and has nothing to do with climate science, and it is questionable whether it should even be counted as an IPCC error.

Some other issues

African crop yields: The IPCC Synthesis Report states: “By 2020, in some countries, yields from rain-fed agriculture could be reduced by up to 50%.” This is properly referenced back to chapter 9.4 of WG2, which says: “In other countries, additional risks that could be exacerbated by climate change include greater erosion, deficiencies in yields from rain-fed agriculture of up to 50% during the 2000-2020 period, and reductions in crop growth period (Agoumi, 2003).”  The Agoumi reference is correct and reported correctly. The Sunday Times, in an article by Jonathan Leake, labels this issue “Africagate” – the main criticism being that Agoumi (2003) is not a peer-reviewed study (see below for our comments on “gray” literature), but a report from the International Institute for Sustainable Development and the Climate Change Knowledge Network, funded by the US Agency for International Development. The report, written by Morroccan climate expert Professor Ali Agoumi, is a summary of technical studies and research conducted to inform Initial National Communications from three countries (Morocco, Algeria and Tunisia) to the United Nations Framework Convention on Climate Change, and is a perfectly legitimate IPCC reference.

It is noteworthy that chapter 9.4 continues with “However, there is the possibility that adaptation could reduce these negative effects (Benhin, 2006).”  Some examples thereof follow, and then it states: “However, not all changes in climate and climate variability will be negative, as agriculture and the growing seasons in certain areas (for example, parts of the Ethiopian highlands and parts of southern Africa such as Mozambique), may lengthen under climate change, due to a combination of increased temperature and rainfall changes (Thornton et al., 2006). Mild climate scenarios project further benefits across African croplands for irrigated and, especially, dryland farms.” (Incidentally, the Benhin and Thornton references are also “gray”, but nobody has complained about them. Could there be double standards amongst the IPCC’s critics?)

Chapter 9.4 to us sounds like a balanced discussion of potential risks and benefits, based on the evidence available at the time–hardly the stuff for shrill “Africagate!” cries. If the IPCC can be criticized here, it is that in condensing these results for its Synthesis Report, important nuance and qualification were lost – especially the point that the risk of drought (defined as a 50% downturn in rainfall) “could be exacerbated by climate change”, as chapter 9.4 wrote – rather than being outright caused by climate change.

Trends in disaster losses: Jonathan Leake (again) in The Sunday Times accused the IPCC of wrongly linking global warming to natural disasters. The IPCC in a statement points out errors in Leake’s “misleading and baseless story”, and maintains that the IPCC provided “a balanced treatment of a complicated and important issue”. While we agree with the IPCC here, WG2 did include a debatable graph provided by Robert Muir-Wood (although not in the main report but only as Supplementary Material). It cited a paper by Muir-Wood as its source although that paper doesn’t include the graph, only the analysis that it is based on. Muir-Wood himself has gone on record to say that the IPCC has fairly represented his research findings and that it was appropriate to include them in the report. In our view there is no IPCC error here; at best there is a difference of opinion. Obviously, not every scientist will always agree with assessments made by the IPCC author teams.

Amazon forest dieback: Leake (yet again), with “research” by skeptic Richard North, has also promoted “Amazongate” with a story regarding a WG2 statement on the future of Amazonian forests under a drying climate.  The contested IPCC statement reads: “Up to 40% of the Amazonian forests could react drastically to even a slight reduction in precipitation; this means that the tropical vegetation, hydrology and climate system in South America could change very rapidly to another steady state, not necessarily producing gradual changes between the current and the future situation (Rowell and Moore, 2000).”  Leake’s problem is with the Rowell and Moore reference, a WWF report.

The roots of the story are in two blog pieces by North, in which he first claims that the IPCC assertions attributed to the WWF report are not actually in that report. Since this claim was immediately shown to be false,  North then argued that the WWF report’s basis for their statement (a 1999 Nature article by Nepstad et al.) dealt only with the effects of logging and fire –not drought– on Amazonian forests. To these various claims Nepstad has now responded, noting that the IPCC statement is in fact correct. The only issue is that the IPCC cited the WWF report rather than the underlying peer-reviewed papers by Nepstad et al. These studies actually provide the  basis for the IPCC’s estimate on Amazonian sensitivity to drought. Investigations of the correspondence between Leake, scientists, and a BBC reporter (see here and here and here) show that Leake ignored or misrepresented explanatory information given to him by Nepstad and another expert, Simon Lewis, and published his incorrect story anyway. This “issue” is thus completely without merit.

Gray literature: The IPCC cites 18,000 references in the AR4; the vast majority of these are peer-reviewed scientific journal papers. The IPCC maintains a clear guideline on the responsible use of so-called “gray” literature, which are typically reports by other organizations or governments. Especially for Working Groups 2 and 3 (but in some cases also for 1) it is indispensable to use gray sources, since many valuable data are published in them: reports by government statistics offices, the International Energy Agency, World Bank, UNEP and so on. This is particularly true when it comes to regional impacts in the least developed countries, where knowledgeable local experts exist who have little chance, or impetus, to publish in international science journals.

Reports by non-governmental organizations like the WWF can be used (as in the Himalaya glacier and Amazon forest cases) but any information from them needs to be carefully checked (this guideline was not followed in the former case). After all, the role of the IPCC is to assess information, not just compile anything it finds.  Assessment involves a level of critical judgment, double-checking, weighing supporting and conflicting pieces of evidence, and a critical appreciation of the methodology used to obtain the results. That is why leading researchers need to write the assessment reports – rather than say, hiring graduate students to compile a comprehensive literature review.

Media distortions

To those familiar with the science and the IPCC’s work, the current media discussion is in large part simply absurd and surreal. Journalists who have never even peeked into the IPCC report are now outraged that one wrong number appears on page 493 of Volume 2. We’ve met TV teams coming to film a report on the IPCC reports’ errors, who were astonished when they held one of the heavy volumes in hand, having never even seen it. They told us frankly that they had no way to make their own judgment; they could only report what they were being told about it. And there are well-organized lobby forces with proper PR skills that make sure these journalists are being told the “right” story. That explains why some media stories about what is supposedly said in the IPCC reports can easily be falsified simply by opening the report and reading. Unfortunately, as a broad-based volunteer effort with only minimal organizational structure the IPCC is not in a good position to rapidly counter misinformation.

One near-universal meme of the media stories on the Himalaya mistake was that this was “one of the most central predictions of the IPCC” – apparently in order to make the error look more serious than it was.  However, this prediction does not appear in any of the IPCC Summaries for Policy Makers, nor in the Synthesis Report (which at least partly explains why it went unnoticed for years). None of the media reports that we saw properly explained that Volume 1 (which is where projections of physical climate changes belong) has an extensive and entirely valid discussion of glacier loss.

What apparently has happened is that interested quarters, after the Himalyan glacier story broke, have sifted through the IPCC volumes with a fine-toothed comb, hoping to find more embarrassing errors. They have actually found precious little, but the little they did find was promptly hyped into Seagate, Africagate, Amazongate and so on. This has some similarity to the CRU email theft, where precious little was discovered from among thousands of emails, but a few sentences were plucked out of context, deliberately misinterpreted (like “hide the decline”) and then hyped into “Climategate”.

As lucidly analysed by Tim Holmes, there appear to be a few active leaders of this misinformation parade in the media. Jonathan Leake is carrying the ball on this, but his stories contain multiple errors, misrepresentations and misquotes. There also is a sizeable contingent of me-too journalism that is simply repeating the stories but not taking the time to form a well-founded view on the topics. Typically they report on various “allegations”, such as these  against the IPCC, similar to reporting that the CRU email hack lead to “allegations of data manipulation”. Technically it isn’t even wrong that there were such allegations. But isn’t it the responsibility of the media to actually investigate whether allegations have any merit before they decide to repeat them?

Leake incidentally attacked the scientific work of one of us (Stefan) in a Sunday Times article in January. This article was rather biased and contained some factual errors that Stefan asked to be corrected. He has received no response, nor was any correction made. Two British scientists quoted by Leake – Jonathan Gregory and Simon Holgate – independently wrote to Stefan after the article appeared to say they had been badly misquoted. One of them wrote that the experience with Leake had made him “reluctant to speak to any journalist about any subject at all”.

Does the IPCC need to change?

The IPCC has done a very good job so far, but certainly there is room for improvement. The review procedures could be organized better, for example. Until now, anyone has been allowed to review any part of the IPCC drafts they liked, but there was no coordination in the sense that say, a glacier expert was specifically assigned to double-check parts of the WG2 chapter on Asia. Such a practice would likely have caught the Himalayan glacier mistake. Another problem has been that reports of all three working groups had to be completed nearly at the same time, making it hard for WG2 to properly base their discussions on the conclusions and projections from WG1. This has already been improved on for the AR5, for which the WG2 report can be completed six months after the WG1 report.

Also, these errors revealed that the IPCC had no mechanism to publish errata. Since a few errors will inevitably turn up in a 2800-page report, obviously an avenue is needed to publish errata as soon as errors are identified.

Is climate science sound?

In some media reports the impression has been given that even the fundamental results of climate change science are now in question, such as whether humans are in fact changing the climate, causing glacier melt, sea level rise and so on. The IPCC does not carry out primary research, and hence any mistakes in the IPCC reports do not imply that any climate research itself is wrong. A reference to a poor report or an editorial lapse by IPCC authors obviously does not undermine climate science. Doubting basic results of climate science based on the recent claims against the IPCC is particularly ironic since none of the real or supposed errors being discussed are even in the Working Group 1 report, where the climate science basis is laid out.

To be fair to our colleagues from WG2 and WG3, climate scientists do have a much simpler task. The system we study is ruled by the well-known laws of physics, there is plenty of hard data and peer-reviewed studies, and the science is relatively mature. The greenhouse effect was discovered in 1824 by Fourier, the heat trapping properties of CO2 and other gases were first measured by Tyndall in 1859, the climate sensitivity to CO2 was first computed in 1896 by Arrhenius, and by the 1950s the scientific foundations were pretty much understood.

Do the above issues suggest “politicized science”, deliberate deceptions or a tendency towards alarmism on the part of IPCC? We do not think there is any factual basis for such allegations. To the contrary, large groups of (inherently cautious) scientists attempting to reach a consensus in a societally important collaborative document is a prescription for reaching generally “conservative” conclusions. And indeed, before the recent media flash broke out, the real discussion amongst experts was about the AR4 having underestimated, not exaggerated, certain aspects of climate change. These include such important topics as sea level rise and sea ice decline (see the sea ice and sea level chapters of the Copenhagen Diagnosis), where the data show that things are changing faster than the IPCC expected.

Overall then, the IPCC assessment reports reflect the state of scientific knowledge very well. There have been a few isolated errors, and these have been acknowledged and corrected. What is seriously amiss is something else: the public perception of the IPCC, and of climate science in general, has been massively distorted by the recent media storm. All of these various “gates” – Climategate, Amazongate, Seagate, Africagate, etc., do not represent scandals of the IPCC or of climate science. Rather, they are the embarrassing battle-cries of a media scandal, in which a few journalists have misled the public with grossly overblown or entirely fabricated pseudogates, and many others have naively and willingly followed along without seeing through the scam. It is not up to us as climate scientists to clear up this mess – it is up to the media world itself to put this right again, e.g. by publishing proper analysis pieces like the one of Tim Holmes and by issuing formal corrections of their mistaken reporting. We will follow with great interest whether the media world has the professional and moral integrity to correct its own errors.

PS. A new book by Realclimate-authors David Archer and Stefan Rahmstorf critically discussing the main findings of the AR4 (all three volumes) is just out: The Climate Crisis. None of the real or alleged errors are in this book, since none of those contentious statements plucked from the thousands of pages appeared to be “main findings” that needed to be discussed in a 250-page summary.

PPS. Same thing for Mike’s book Dire Predictions: Understanding Global Warming, which bills itself as “The illustrated guide to the findings of the IPCC”. Or Gavin’s “Climate Change: Picturing the Science” – which does include a few pictures of disappearing glaciers though!

Guest Commentary by Jim Bouldin (UC Davis)

How much additional carbon dioxide will be released to, or removed from, the atmosphere, by the oceans and the biosphere in response to global warming over the next century? That is an important question, and David Frank and his Swiss coworkers at WSL have just published an interesting new approach to answering it. They empirically estimate the distribution of gamma, the temperature-induced carbon dioxide feedback to the climate system, given the current state of the knowledge of reconstructed temperature, and carbon dioxide concentration, over the last millennium. It is a macro-scale approach to constraining this parameter; it does not attempt to refine our knowledge about carbon dioxide flux pathways, rates or mechanisms. Regardless of general approach or specific results, I like studies like this. They bring together results from actually or potentially disparate data inputs and methods, which can be hard to keep track of, into a systematic framework. By organizing, they help to clarify, and for that there is much to be said.

Gamma has units in ppmv per ºC. It is thus the inverse of climate sensitivity, where CO2 is the forcing and T is the response. Carbon dioxide can, of course, act as both a forcing and a (relatively slow) feedback; slow at least when compared to faster feedbacks like water vapor and cloud changes. Estimates of the traditional climate sensitivity, e.g. Charney et al., (1979) are thus not affected by the study. Estimates of more broadly defined sensitivities that include slower feedbacks, (e.g. Lunt et al. (2010), Pagani et al. (2010)), could be however.

Existing estimates of gamma come primarily from analyses of coupled climate-carbon cycle (C4) models (analyzed in Friedlingstein et al., 2006), and a small number of empirical studies. The latter are based on a limited set of assumptions regarding historic temperatures and appropriate methods, while the models display a wide range of sensitivities depending on assumptions inherent to each. Values of gamma are typically positive in these studies (i.e. increased T => increased CO2).

To estimate gamma, the authors use an experimental (“ensemble”) calibration approach, by analyzing the time courses of reconstructed Northern Hemisphere T estimates, and ice core CO2 levels, from 1050 to 1800, AD. This period represents a time when both high resolution T and CO2 estimates exist, and in which the confounding effects of other possible causes of CO2 fluxes are minimized, especially the massive anthropogenic input since 1800. That input could completely swamp the temperature signal; the authors’ choice is thus designed to maximize the likelihood of detecting the T signal on CO2. The T estimates are taken from the recalibration of nine proxy-based studies from the last decade, and the CO2 from 3 Antarctic ice cores. Northern Hemisphere T estimates are used because their proxy sample sizes (largely dendro-based) are far higher than in the Southern Hemisphere. However, the results are considered globally applicable, due to the very strong correlation between hemispheric and global T values in the instrumental record (their Figure S3, r = 0.96, HadCRUT basis), and also of ice core and global mean atmospheric CO2.

The authors systematically varied both the proxy T data sources and methodologicalvariables that influence gamma, and then examined the distribution of the nearly 230,000 resulting values. The varying data sources include the nine T reconstructions (Fig 1), while the varying methods include things like the statistical smoothing method, and the time intervals used to both calibrate the proxy T record against the instrumental record, and to estimate gamma.

Figure 1. The nine temperature reconstructions (a), and 3 ice core CO2 records (b), used in the study.

Some other variables were fixed, most notably the calibration method relating the proxy and instrumental temperatures (via equalization of the mean and variance for each, over the chosen calibration interval). The authors note that this approach is not only among the mathematically simplest, but also among the best at retaining the full variance (Lee et al, 2008), and hence the amplitude, of the historic T record. This is important, given the inherent uncertainty in obtaining a T signal, even with the above-mentioned considerations regarding the analysis period chosen. They chose the time lag, ranging up to +/- 80 years, which maximized the correlation between T and CO2. This was to account for the inherent uncertainty in the time scale, and even the direction of causation, of the various physical processes involved. They also estimated the results that would be produced from 10 C4 models analyzed by Friedlingstein (2006), over the same range of temperatures (but shorter time periods).

So what did they find?

In the highlighted result of the work, the authors estimate the mean and median of gamma to be 10.2 and 7.7 ppm/ºC respectively, but, as indicated by the difference in the two, with a long tail to the right (Fig. 2). The previous empirical estimates, by contrast, come in much higher–about 40 ppm/degree. The choice of the proxy reconstruction used, and the target time period analyzed, had the largest effect on the estimates. The estimates from the ten C4 models, were higher on average; it is about twice as likely that the empirical estimates fall in the model estimates? lower quartile as in the upper. Still, six of the ten models evaluated produced results very close to the empirical estimates, and the models’ range of estimates does not exclude those from the empirical methods.

Figure 2. Distribution of gamma. Red values are from 1050-1550, blue from 1550-1800.

Are these results cause for optimism regarding the future? Well the problem with knowing the future, to flip the famous Niels Bohr quote, is that it involves prediction.

The question is hard to answer. Empirically oriented studies are inherently limited in applicability to the range of conditions they evaluate. As most of the source reconstructions used in the study show, there is no time period between 1050 and 1800, including the medieval times, which equals the global temperature state we are now in; most of it is not even close. We are in a no-analogue state with respect to mechanistic, global-scale understanding of the inter-relationship of the carbon cycle and temperature, at least for the last two or three million years. And no-analogue states are generally not a real comfortable place to be, either scientifically or societally.

Still, based on these low estimates of gamma, the authors suggest that surprises over the next century may be unlikely. The estimates are supported by the fact that more than half of the C4-based (model) results were quite close (within a couple of ppm) to the median values obtained from the empirical analysis, although the authors clearly state that the shorter time periods that the models were originally run over makes apples to apples comparisons with the empirical results tenuous. Still, this result may be evidence that the carbon cycle component of these models have, individually or collectively, captured the essential physics and biology needed to make them useful for predictions into the multi-decadal future. Also, some pre-1800, temperature independent CO2 fluxes could have contributed to the observed CO2 variation in the ice cores, which would tend to exaggerate the empirically-estimated values. The authors did attempt to control for the effects of land use change, but noted that modeled land use estimates going back 1000 years are inherently uncertain. Choosing the time lag that maximizes the T to CO2 correlation could also bias the estimates high.

On the other hand, arguments could also be made that the estimates are low. Figure 2 shows that the authors also performed their empirical analyses within two sub-intervals (1050-1550, and 1550-1800). Not only did the mean and variance differ significantly between the two (mean/s.d. of 4.3/3.5 versus 16.1/12.5 respectively), but the R squared values of the many regressions were generally much higher in the late period than in the early (their Figure S6). Given that the proxy sample size for all temperature reconstructions generally drops fairly drastically over the past millennium, especially before their 1550 dividing line, it seems at least reasonably plausible that the estimates from the later interval are more realistic. The long tail–the possibility of much higher values of gamma–also comes mainly from the later time interval, so values of gamma from say 20 to 60 ppm/ºC (e.g. Cox and Jones, 2008) certainly cannot be excluded.

But this wrangling over likely values may well be somewhat moot, given the real world situation. Even if the mean estimates as high as say 20 ppm/ºC are more realistic, this feedback rate still does not compare to the rate of increase in CO2 resulting from fossil fuel burning, which at recent rates would exceed that amount in between one and two decades.

I found some other results of this study interesting. One such involved the analysis of time lags. The authors found that in 98.5% of their regressions, CO2 lagged temperature. There will undoubtedly be those who interpret this as evidence that CO2 cannot be a driver of temperature, a common misinterpretation of the ice core record. Rather, these results from the past millennium support the usual interpretation of the ice core record over the later Pleistocene, in which CO2 acts as a feedback to temperature changes initiated by orbital forcings (see e.g. the recent paper by Ganopolski and Roche (2009)).

The study also points up the need, once again, to further constrain the carbon cycle budget. The fact that a pre-1800 time period had to be used to try to detect a signal indicates that this type of analysis is not likely to be sensitive enough to figure out how, or even if, gamma is changing in the future. The only way around that problem is via tighter constraints on the various pools and fluxes of the carbon cycle, especially those related to the terrestrial component. There is much work to be done there.

References

Charney, J.G., et al. Carbon Dioxide and Climate: A Scientific Assessment. National Academy of Sciences, Washington, DC (1979).

Cox, P. & Jones, C. Climate change – illuminating the modern dance of climate and CO2. Science 321, 1642-1644 (2008).

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A quick post for commentary on the new Solomon et al paper in Science express. We’ll try and get around to discussing this over the weekend, but in the meantime I’ve moved some comments over. There is some commentary on this at DotEarth, and some media reports on the story – some good, some not so good. It seems like a topic that is ripe for confusion, and so here are a few quick clarifications that are worth making.

First of all, this is a paper about internal variability of the climate system in the last decade, not on additional factors that drive climate. Second, this is a discussion about stratospheric water vapour (10 to 15 km above the surface), not water vapour in general. Stratospheric water vapour comes from two sources – the uplift of tropospheric water through the very cold tropical tropopause (both as vapour and as condensate), and the oxidation of methane in the upper stratosphere (CH4+2O2 –> CO2 + 2H2O NB: this is just a schematic, the actual chemical pathways are more complicated). There isn’t very much of it (between 3 and 6 ppmv), and so small changes (~0.5 ppmv) are noticeable.

The decreases seen in this study are in the lower stratosphere and are likely dominated by a change in the flux of water through the tropopause. A change in stratospheric water vapour because of the increase in methane over the industrial period would be a forcing of the climate (and is one of the indirect effects of methane we discussed last year), but a change in the tropopause flux is a response to other factors in the climate system. These might include El Nino/La Nina events, increases in Asian aerosols, or solar impacts on near-tropopause ozone – but this is not addressed in the paper and will take a little more work to figure out.

Update: This last paragraph was probably not as clear as it should be. If the lower stratospheric water vapour (LSWV) is relaxing back to some norm after the 1997/1998 El Nino, then what we are seeing would be internal variability in the system which might have some implications for feedbacks to increasing GHGs, and my estimate of that would be that this would be an amplifying feedback (warmer SSTs leading to more LSWV). If we are seeing changes to the tropopause temperatures as an indirect impact from increased Asian aerosol emissions or solar-driven ozone changes, then this might be better thought of as impacting the efficacy of those forcings rather than implying some sensitivity change.

The study includes an estimate of the effect of the observed stratospheric water decadal decrease by calculating the radiation flux with and without the change, and comparing this to the increase in CO2 forcing over the same period. This implicitly assumes that the change can be regarded as a forcing. However, whether that is an appropriate calculation or not needs some careful consideration. Finally, no-one has yet looked at whether climate models (which have plenty of decadal variability too) have phenomena that resemble these observations that might provide some insight into the causes.

Like all human endeavours, the IPCC is not perfect. Despite the enormous efforts devoted to producing its reports with the multiple levels of peer review, some errors will sneak through. Most of these will be minor and inconsequential, but sometimes they might be more substantive. As many people are aware (and as John Nieslen-Gammon outlined in a post last month and Rick Piltz goes over today), there is a statement in the second volume of the IPCC (WG2), concerning the rate at which Himalayan glaciers are receding that is not correct and not properly referenced.

The statement, in a chapter on climate impacts in Asia, was that the likelihood of the Himalayan glaciers “disappearing by the year 2035″ was “very high” if the Earth keeps warming at the current rate (WG 2, Ch. 10, p493), and was referenced to a World Wildlife Fund 2005 report. Examining the drafts and comments (available here), indicates that the statement was barely commented in the reviews, and that the WWF (2005) reference seems to have been a last minute addition (it does not appear in the First- or Second- Order Drafts). This claim did not make it into the summary for policy makers, nor the overall synthesis report, and so cannot be described as a ‘central claim’ of the IPCC. However, the statement has had some press attention since the report particularly in the Indian press, at least according to Google News, even though it was not familiar to us before last month.

It is therefore obvious that this error should be corrected (via some kind of corrigendum to the WG2 report perhaps), but it is important to realise that this doesn’t mean that Himalayan glaciers are doing just fine. They aren’t, and there may be serious consequences for water resources as the retreat continues. See also this review paper (Ren et al, 2006) on a subset of these glaciers.

East Rongbuk glacier just below Mt. Everest has lost 3-400 ft of ice in this area since 1921.

More generally, peer-review works to make the IPCC reports credible because many different eyes with different perspectives and knowledge look over the same text. This tends to make the resulting product reflect more than just the opinion of a single author. In this case, it appears that not enough people with relevant experience saw this text, or if they saw it, did not comment publicly. This might be related to the fact that this text was in the Working Group 2 report on impacts, which does not get the same amount of attention from the physical science community than does the higher profile WG 1 report (which is what people associated with RC generally look at). In WG1, the statements about continued glacier retreat are much more general and the rules on citation of non-peer reviewed literature was much more closely adhered to. However, in general, the science of climate impacts is less clear than the physical basis for climate change, and the literature is thinner, so there is necessarily more ambiguity in WG 2 statements.

In future reports (and the organisation for AR5 in 2013 is now underway), extra efforts will be needed to make sure that the links between WG1 and the other two reports are stronger, and that the physical science community should be encouraged to be more active in the other groups.

In summary, the measure of an organisation is not determined by the mere existence of errors, but in how it deals with them when they crop up. The current discussion about Himalayan glaciers is therefore a good opportunity for the IPCC to further improve their procedures and think more about what the IPCC should be doing in the times between the main reports.

Update: This backgrounder presented by Kargel et al AGU this December is the best summary of the current state of the Himalayas and the various sources of misinformation that are floating around. It covers this issue, the Raina report and the recent Lau et al paper.

This is Hansen et al’s end of year summary for 2009 (with a couple of minor edits). Update: A final version of this text is available here.

If It’s That Warm, How Come It’s So Damned Cold? 

 
by James Hansen, Reto Ruedy, Makiko Sato, and Ken Lo
 
The past year, 2009, tied as the second warmest year in the 130 years of global instrumental temperature records, in the surface temperature analysis of the NASA Goddard Institute for Space Studies (GISS). The Southern Hemisphere set a record as the warmest year for that half of the world. Global mean temperature, as shown in Figure 1a, was 0.57°C (1.0°F) warmer than climatology (the 1951-1980 base period). Southern Hemisphere mean temperature, as shown in Figure 1b, was 0.49°C (0.88°F) warmer than in the period of climatology.

Figure 1. (a) GISS analysis of global surface temperature change. Green vertical bar is estimated 95 percent confidence range (two standard deviations) for annual temperature change. (b) Hemispheric temperature change in GISS analysis. (Base period is 1951-1980. This base period is fixed consistently in GISS temperature analysis papers – see References. Base period 1961-1990 is used for comparison with published HadCRUT analyses in Figures 3 and 4.)

The global record warm year, in the period of near-global instrumental measurements (since the late 1800s), was 2005. Sometimes it is asserted that 1998 was the warmest year. The origin of this confusion is discussed below. There is a high degree of interannual (year‐to‐year) and decadal variability in both global and hemispheric temperatures. Underlying this variability, however, is a long‐term warming trend that has become strong and persistent over the past three decades. The long‐term trends are more apparent when temperature is averaged over several years. The 60‐month (5‐year) and 132 month (11‐year) running mean temperatures are shown in Figure 2 for the globe and the hemispheres. The 5‐year mean is sufficient to reduce the effect of the El Niño – La Niña cycles of tropical climate. The 11‐year mean minimizes the effect of solar variability – the brightness of the sun varies by a measurable amount over the sunspot cycle, which is typically of 10‐12 year duration.

Figure 2. 60‐month (5‐year) and 132 month (11‐year) running mean temperatures in the GISS analysis of (a) global and (b) hemispheric surface temperature change. (Base period is 1951‐1980.)

There is a contradiction between the observed continued warming trend and popular perceptions about climate trends. Frequent statements include: “There has been global cooling over the past decade.” “Global warming stopped in 1998.” “1998 is the warmest year in the record.” Such statements have been repeated so often that most of the public seems to accept them as being true. However, based on our data, such statements are not correct. The origin of this contradiction probably lies in part in differences between the GISS and HadCRUT temperature analyses (HadCRUT is the joint Hadley Centre/University of East Anglia Climatic Research Unit temperature analysis). Indeed, HadCRUT finds 1998 to be the warmest year in their record. In addition, popular belief that the world is cooling is reinforced by cold weather anomalies in the United States in the summer of 2009 and cold anomalies in much of the Northern Hemisphere in December 2009. Here we first show the main reason for the difference between the GISS and HadCRUT analyses. Then we examine the 2009 regional temperature anomalies in the context of global temperatures.

Figure 3. Temperature anomalies in 1998 (left column) and 2005 (right column). Top row is GISS analysis, middle row is HadCRUT analysis, and bottom row is the GISS analysis masked to the same area and resolution as the HadCRUT analysis. [Base period is 1961‐1990.]

Figure 3 shows maps of GISS and HadCRUT 1998 and 2005 temperature anomalies relative to base period 1961‐1990 (the base period used by HadCRUT). The temperature anomalies are at a 5 degree‐by‐5 degree resolution for the GISS data to match that in the HadCRUT analysis. In the lower two maps we display the GISS data masked to the same area and resolution as the HadCRUT analysis. The “masked” GISS data let us quantify the extent to which the difference between the GISS and HadCRUT analyses is due to the data interpolation and extrapolation that occurs in the GISS analysis. The GISS analysis assigns a temperature anomaly to many gridboxes that do not contain measurement data, specifically all gridboxes located within 1200 km of one or more stations that do have defined temperature anomalies.

The rationale for this aspect of the GISS analysis is based on the fact that temperature anomaly patterns tend to be large scale. For example, if it is an unusually cold winter in New York, it is probably unusually cold in Philadelphia too. This fact suggests that it may be better to assign a temperature anomaly based on the nearest stations for a gridbox that contains no observing stations, rather than excluding that gridbox from the global analysis. Tests of this assumption are described in our papers referenced below.

Figure 4. Global surface temperature anomalies relative to 1961‐1990 base period for three cases: HadCRUT, GISS, and GISS anomalies limited to the HadCRUT area. [To obtain consistent time series for the HadCRUT and GISS global means, monthly results were averaged over regions with defined temperature anomalies within four latitude zones (90N‐25N, 25N‐Equator, Equator‐25S, 25S‐90S); the global average then weights these zones by the true area of the full zones, and the annual means are based on those monthly global means.]

Figure 4 shows time series of global temperature for the GISS and HadCRUT analyses, as well as for the GISS analysis masked to the HadCRUT data region. This figure reveals that the differences that have developed between the GISS and HadCRUT global temperatures during the past few decades are due primarily to the extension of the GISS analysis into regions that are excluded from the HadCRUT analysis. The GISS and HadCRUT results are similar during this period, when the analyses are limited to exactly the same area. The GISS analysis also finds 1998 as the warmest year, if analysis is limited to the masked area. The question then becomes: how valid are the extrapolations and interpolation in the GISS analysis? If the temperature anomaly scale is adjusted such that the global mean anomaly is zero, the patterns of warm and cool regions have realistic‐looking meteorological patterns, providing qualitative support for the data extensions. However, we would like a quantitative measure of the uncertainty in our estimate of the global temperature anomaly caused by the fact that the spatial distribution of measurements is incomplete. One way to estimate that uncertainty, or possible error, can be obtained via use of the complete time series of global surface temperature data generated by a global climate model that has been demonstrated to have realistic spatial and temporal variability of surface temperature. We can sample this data set at only the locations where measurement stations exist, use this sub‐sample of data to estimate global temperature change with the GISS analysis method, and compare the result with the “perfect” knowledge of global temperature provided by the data at all gridpoints.

1880‐1900 1900‐1950 1960‐2008 Meteorological Stations 0.2 0.15 0.08 Land‐Ocean Index 0.08 0.05 0.05

Table 1. Two‐sigma error estimate versus period for meteorological stations and land‐ocean index.

Table 1 shows the derived error due to incomplete coverage of stations. As expected, the error was larger at early dates when station coverage was poorer. Also the error is much larger when data are available only from meteorological stations, without ship or satellite measurements for ocean areas. In recent decades the 2‐sigma uncertainty (95 percent confidence of being within that range, ~2‐3 percent chance of being outside that range in a specific direction) has been about 0.05°C. The incomplete coverage of stations is the primary cause of uncertainty in comparing nearby years, for which the effect of more systematic errors such as urban warming is small.

Additional sources of error become important when comparing temperature anomalies separated by longer periods. The most well‐known source of long‐term error is “urban warming”, human‐made local warming caused by energy use and alterations of the natural environment. Various other errors affecting the estimates of long‐term temperature change are described comprehensively in a large number of papers by Tom Karl and his associates at the NOAA National Climate Data Center. The GISS temperature analysis corrects for urban effects by adjusting the long‐term trends of urban stations to be consistent with the trends at nearby rural stations, with urban locations identified either by population or satellite‐observed night lights. In a paper in preparation we demonstrate that the population and night light approaches yield similar results on global average. The additional error caused by factors other than incomplete spatial coverage is estimated to be of the order of 0.1°C on time scales of several decades to a century, this estimate necessarily being partly subjective. The estimated total uncertainty in global mean temperature anomaly with land and ocean data included thus is similar to the error estimate in the first line of Table 1, i.e., the error due to limited spatial coverage when only meteorological stations are included.

Now let’s consider whether we can specify a rank among the recent global annual temperatures, i.e., which year is warmest, second warmest, etc. Figure 1a shows 2009 as the second warmest year, but it is so close to 1998, 2002, 2003, 2006, and 2007 that we must declare these years as being in a virtual tie as the second warmest year. The maximum difference among these in the GISS analysis is ~0.03°C (2009 being the warmest among those years and 2006 the coolest). This range is approximately equal to our 1‐sigma uncertainty of ~0.025°C, which is the reason for stating that these five years are tied for second warmest.

The year 2005 is 0.061°C warmer than 1998 in our analysis. So how certain are we that 2005 was warmer than 1998? Given the standard deviation of ~0.025°C for the estimated error, we can estimate the probability that 1998 was warmer than 2005 as follows. The chance that 1998 is 0.025°C warmer than our estimated value is about (1 – 0.68)/2 = 0.16. The chance that 2005 is 0.025°C cooler than our estimate is also 0.16. The probability of both of these is ~0.03 (3 percent). Integrating over the tail of the distribution and accounting for the 2005‐1998 temperature difference being 0.61°C alters the estimate in opposite directions. For the moment let us just say that the chance that 1998 is warmer than 2005, given our temperature analysis, is at most no more than about 10 percent. Therefore, we can say with a reasonable degree of confidence that 2005 is the warmest year in the period of instrumental data.

Figure 5. (a) global map of December 2009 anomaly, (b) global map of Jun‐Jul‐Aug 2009 anomaly. #4 and #2 indicate that December 2009 and JJA are the 4th and 2nd warmest globally for those periods.

What about the claim that the Earth’s surface has been cooling over the past decade? That issue can be addressed with a far higher degree of confidence, because the error due to incomplete spatial coverage of measurements becomes much smaller when averaged over several years. The 2‐sigma error in the 5‐year running‐mean temperature anomaly shown in Figure 2, is about a factor of two smaller than the annual mean uncertainty, thus 0.02‐0.03°C. Given that the change of 5‐year‐mean global temperature anomaly is about 0.2°C over the past decade, we can conclude that the world has become warmer over the past decade, not cooler.

Why are some people so readily convinced of a false conclusion, that the world is really experiencing a cooling trend? That gullibility probably has a lot to do with regional short‐term temperature fluctuations, which are an order of magnitude larger than global average annual anomalies. Yet many lay people do understand the distinction between regional short‐term anomalies and global trends. For example, here is comment posted by “frogbandit” at 8:38p.m. 1/6/2010 on City Bright blog:

“I wonder about the people who use cold weather to say that the globe is cooling. It forgets that global warming has a global component and that its a trend, not an everyday thing. I hear people down in the lower 48 say its really cold this winter. That ain’t true so far up here in Alaska. Bethel, Alaska, had a brown Christmas. Here in Anchorage, the temperature today is 31[ºF]. I can’t say based on the fact Anchorage and Bethel are warm so far this winter that we have global warming. That would be a really dumb argument to think my weather pattern is being experienced even in the rest of the United States, much less globally.”

What frogbandit is saying is illustrated by the global map of temperature anomalies in December 2009 (Figure 5a). There were strong negative temperature anomalies at middle latitudes in the Northern Hemisphere, as great as ‐8°C in Siberia, averaged over the month. But the temperature anomaly in the Arctic was as great as +7°C. The cold December perhaps reaffirmed an impression gained by Americans from the unusually cool 2009 summer. There was a large region in the United States and Canada in June‐July‐August with a negative temperature anomaly greater than 1°C, the largest negative anomaly on the planet.

Figure 6. Arctic Oscillation (AO) Index. Positive values of the AO index indicate high low pressure in the polar region and thus a tendency for strong zonal winds that minimize cold air outbreaks to middle latitudes. Blue dots are monthly means and the red curve is the 60‐month (5‐year) running mean.

How do these large regional temperature anomalies stack up against an expectation of, and the reality of, global warming? How unusual are these regional negative fluctuations? Do they have any relationship to global warming? Do they contradict global warming?

It is obvious that in December 2009 there was an unusual exchange of polar and mid‐latitude air in the Northern Hemisphere. Arctic air rushed into both North America and Eurasia, and, of course, it was replaced in the polar region by air from middle latitudes. The degree to which Arctic air penetrates into middle latitudes is related to the Arctic Oscillation (AO) index, which is defined by surface atmospheric pressure patterns and is plotted in Figure 6. When the AO index is positive surface pressure is high low in the polar region. This helps the middle latitude jet stream to blow strongly and consistently from west to east, thus keeping cold Arctic air locked in the polar region. When the AO index is negative there tends to be low high pressure in the polar region, weaker zonal winds, and greater movement of frigid polar air into middle latitudes.

Figure 6 shows that December 2009 was the most extreme negative Arctic Oscillation since the 1970s. Although there were ten cases between the early 1960s and mid 1980s with an AO index more extreme than ‐2.5, there were no such extreme cases since then until last month. It is no wonder that the public has become accustomed to the absence of extreme blasts of cold air.

Figure 7. Temperature anomaly from GISS analysis and AO index from NOAA National Weather Service Climate Prediction Center. United States mean refers to the 48 contiguous states.

Figure 7 shows the AO index with greater temporal resolution for two 5‐year periods. It is obvious that there is a high degree of correlation of the AO index with temperature in the United States, with any possible lag between index and temperature anomaly less than the monthly temporal resolution. Large negative anomalies, when they occur, are usually in a winter month. Note that the January 1977 temperature anomaly, mainly located in the Eastern United States, was considerably stronger than the December 2009 anomaly. [There is nothing magic about a 31 day window that coincides with a calendar month, and it could be misleading. It may be more informative to look at a 30‐day running mean and at the Dec‐Jan‐Feb means for the AO index and temperature anomalies.]

The AO index is not so much an explanation for climate anomaly patterns as it is a simple statement of the situation. However, John (Mike) Wallace and colleagues have been able to use the AO description to aid consideration of how the patterns may change as greenhouse gases increase. A number of papers, by Wallace, David Thompson, and others, as well as by Drew Shindell and others at GISS, have pointed out that increasing carbon dioxide causes the stratosphere to cool, in turn causing on average a stronger jet stream and thus a tendency for a more positive Arctic Oscillation. Overall, Figure 6 shows a tendency in the expected sense. The AO is not the only factor that might alter the frequency of Arctic cold air outbreaks. For example, what is the effect of reduced Arctic sea ice on weather patterns? There is not enough empirical evidence since the rapid ice melt of 2007. We conclude only that December 2009 was a highly anomalous month and that its unusual AO can be described as the “cause” of the extreme December weather.

We do not find a basis for expecting frequent repeat occurrences. On the contrary. Figure 6 does show that month‐to‐month fluctuations of the AO are much larger than its long term trend. But temperature change can be caused by greenhouse gases and global warming independent of Arctic Oscillation dynamical effects.

Figure 8. Global maps 4 season temperature anomalies for ~2009. (Note that Dec is December 2008. Base period is 1951‐1980.)

Figure 9. Global maps 4 season temperature anomaly trends for period 1950‐2009.

So let’s look at recent regional temperature anomalies and temperature trends. Figure 8 shows seasonal temperature anomalies for the past year and Figure 9 shows seasonal temperature change since 1950 based on local linear trends. The temperature scales are identical in Figures 8 and 9. The outstanding characteristic in comparing these two figures is that the magnitude of the 60 year change is similar to the magnitude of seasonal anomalies. What this is telling us is that the climate dice are already strongly loaded. The perceptive person who has been around since the 1950s should be able to notice that seasonal mean temperatures are usually greater than they were in the 1950s, although there are still occasional cold seasons.

The magnitude of monthly temperature anomalies is typically 1.5 to 2 times greater than the magnitude of seasonal anomalies. So it is not yet quite so easy to see global warming if one’s figure of merit is monthly mean temperature. And, of course, daily weather fluctuations are much larger than the impact of the global warming trend. The bottom line is this: there is no global cooling trend. For the time being, until humanity brings its greenhouse gas emissions under control, we can expect each decade to be warmer than the preceding one. Weather fluctuations certainly exceed local temperature changes over the past half century. But the perceptive person should be able to see that climate is warming on decadal time scales.

This information needs to be combined with the conclusion that global warming of 1‐2°C has enormous implications for humanity. But that discussion is beyond the scope of this note.

References:
Hansen, J.E., and S. Lebedeff, 1987: Global trends of measured surface air temperature. J. Geophys. Res., 92, 13345‐13372.
Hansen, J., R. Ruedy, J. Glascoe, and Mki. Sato, 1999: GISS analysis of surface temperature change. J. Geophys. Res., 104, 30997‐31022.
Hansen, J.E., R. Ruedy, Mki. Sato, M. Imhoff, W. Lawrence, D. Easterling, T. Peterson, and T. Karl, 2001: A closer look at United States and global surface temperature change. J. Geophys. Res., 106, 23947‐23963.
Hansen, J., Mki. Sato, R. Ruedy, K. Lo, D.W. Lea, and M. Medina‐Elizade, 2006: Global temperature change. Proc. Natl. Acad. Sci., 103, 14288‐14293.

RealClimate is run by a rather loosely organized volunteer consortium of people with day jobs that in and of themselves can be quite consuming of attention. And so it came to pass that the first I learned about Gavin’s interest in the work of Plass was — by reading RealClimate! In fact, David Archer and I have a book due to appear this year from Wiley/Blackwell (The Warming Papers), which is a collection of historic papers on global warming, together with interpretive essays by David and myself. Needless to say, we pay a lot of attention to the seminal work by Plass in this book. His 1956 QJRMS technical paper on radiative transfer, which is largely the basis of his more popular writings on global warming, was one of the papers we chose to reprint in our collection. In reading historic papers, it is easy to fall into the trap of assuming that investigators of the past are working on the basis of the same underlying set of assumptions in common use today. Through a very close reading of the paper, David and I noticed something about the way Plass estimated surface temperature increase, that Gavin and all previous commentators on Plass — including Kaplan himself — seem to have overlooked.

These days, it is fairly common knowledge that determination of surface temperature change requires simultaneous satisfaction of the top-of-atmosphere energy budget and surface energy budget, and that in most circumstances it is the top-of-atmosphere budget that plays by far the leading role. This is one of the many things that Arrhenius got spot-on right in his conceptual framework for computing surface temperature. His computation explicitly takes both balance requirements into account, though substantial inaccuracies were introduced because the onerous computations involved in solving the model pretty much restricted him to a one-layer representation of the atmosphere. Later workers improved on Arrhenius by introducing multiple layers and more accurate spectroscopy, but did not always note the importance of satisfying the top-of-atmosphere balance. I think it seems natural to most people to assume that if one is interested in surface temperature, the surface budget must be the most important thing to look at. Plass, for all his brilliance in computing the radiative effects of CO2, was one of the ones who was led astray by this fallacy.

Since discussions of radiative forcing today are almost invariably based on top-of-atmosphere budgets (or at least top-of- troposphere budgets, which are almost the same thing), it is natural for the modern reader to assume that when a paper quotes a radiative forcing, it must be a top-of-atmosphere forcing. This is what Gavin assumed, but a close reading of the 1956 QJRMS paper shows that this is not, in fact, what Plass was talking about. In that paper, Plass does not get around to turning his voluminous radiative calculations into a surface temperature change until nearly the last page of the paper, and when he does, he spends barely a page explaining the reasoning.

The radiative forcing Plass quotes is actually the increase in downward infrared radiation to the surface, which you get if you double CO2 while holding the atmospheric temperature fixed . This back-radiation increases because increasing the concentration of a greenhouse gas makes the atmosphere a more efficient emitter of infrared radiation, at least up to the point where the lowest bits of the atmosphere emit so well that they essentially have become a blackbody, whereafter the emission to the ground can no longer increase unless the air temperature changes. For Earthlike conditions, the emission from CO2 is nowhere near saturated in this sense (see this post ) , so Plass was entirely correct in inferring an increase in the back-radiation, at least for a relatively dry atmosphere. Adding CO2 to the atmosphere is a bit like turning up the dial on a heat lamp you are lying underneath.

It is in the final stages of the calculation that Plass went wrong. He assumed that the surface would get rid of the extra infrared radiation it was receiving by heating up until it was able to radiate away the excess. This reasoning ignores the fact that radiation is not the only means of exchanging heat between the atmosphere and the surface. There are also turbulent exchanges, including evaporation, and these would tend to limit the surface warming to values far less than the values Plass estimated. Further, when the lower atmosphere is warm and moist, such as in the tropics, the great infrared opacity of the large quantity of water vapor tends to limit the direct effect of CO2 on back-radiation into the surface, which further limits the surface warming if the air temperature is held fixed as Plass did. To be fair, Plass does include a sentence implying that he was concerned about the portion of the retained flux that exited through the top of the atmosphere, but even if one gives the most generous interpretation to what might have been meant by this statement, there is no way to make a consistent calculation out of it, given the use of the surface back-radiation as radiative forcing.

The way the greenhouse effect really works is that adding CO2 reduces the infrared out the top of the atmosphere, which means the planet receives more solar energy than it is getting rid of as infrared out the top. The only way to bring the system back into balance is for the whole troposphere to warm up. It is the corresponding warming of the low level air that drags the surface temperature along with it — an effect left entirely out of Plass’ calculation.

A more quantitative discussion of the way all this works can be found in The Warming Papers, and a yet more advanced discussion of such things can be found in Chapter 6 of my book Principles of Planetary Climate (which at long last has been shipped off to Cambridge University press, animula vagula blandula)

In point of fact, Plass did compute the top-of-atmosphere radiative forcing due to doubling or halving the concentration of CO2. The result is plainly shown in the rightmost graph of his Figure 7, where he shows the vertical profile of upward and downward flux for three different CO2 concentrations. Reading the values from the top of the graph, I get that Plass computes a 3.2 Watt per square meter reduction in the outgoing radiation for a doubling of CO2. This is really quite close to the modern value. Plass does not mention this number, or its importance, anywhere in the text, however. Still, it would be fair to give Plass the credit for the first calculation of top-of-atmosphere radiative forcing using correct modern radiative physics. Though he did not make good use of the calculation himself, the methods he introduced are largely the same as those used by Manabe and Wetherald in 1967, who were the first to put together correct spectroscopy with a correct framework for computing surface temperature, adding in accurate water vapor spectroscopy and the effects of convection along the way.

Thus, while Plass made seminal contributions to radiative transfer, his actual estimate of surface temperature increase cannot be regarded as an improvement over Arrhenius. Plass had better spectroscopy than Arrhenius, but a framework that would not give the right answer no matter how good the radiative transfer was. The point of all this historical deconstruction is not to poke fun at Plass or detract from his contributions. Theories do not spring from scientists full-formed like Athena from the head of Zeuss. Science often proceeds through a series of errors and corrections, and those who move the ball forward are in the thick of this process even if they have made some mistakes. The point is that our current understanding of global warming rests on the shoulders of some of the greatest giants of physics of the past century or more, and myriad lesser but still substantial intellects as well.

So, when push comes to shove, was Plass a Hedgehog or a Fox? The answer is: a bit of both. With regard to computing the radiative fluxes due to CO2, Plass was a true hedgehog — he knew that one thing really, really well, and that had a lasting impact on our science. But in his Tellus article, he also showed himself to be quite a fox, in that by knowing (and explaining) many independent lines of thinking, he helped to revive attention to the wide-ranging importance of CO2 in climate. You could say he was not enough of a fox to have also absorbed the lesson of the importance of top-of-atmosphere balance, known already to Arrhenius. But also, you could say that if you’re going to be a hedgehog and pick one thing to be the central organizing principle of your world view, it had better be a pretty darn universally important thing to know. If you’re going to be a climate hedgehog, the constraint imposed by top-of-atmosphere radiation balance would be a pretty good place to hang your hat.

I said on Friday that I didn’t think that Lindzen and Choi (2009) was obviously nonsense. Well, a number of people have disagreed with me, and in doing so, have presented some of the back story on the how the response was handled. I think this deserves to be more widely known in the hope that it will generate some discussion in the community for how such situations might be dealt with in the future.

From Chris O’Dell:

Given the large number of comments on the peer-review process in general and in the LC09 case in particular, it is probably worthwhile to give a bit more backstory to our Trenberth et al. paper. On my first reading of LC09, I was quite amazed and thought if the results were true, it would be incredible (and, in fact, a good thing!) and hence warranted independent checking. Very simple attempts to reproduce the LC09 numbers simply didn’t work out and revealed some flaws in their process. To find out more, I contacted Dr. Takmeng Wong at NASA Langley, a member of the CERES and ERBE science teams (and major player in the ERBE data set) and found out to my surprise that no one on these teams was a reviewer of LC09. Dr. Wong was doing his own verification of LC09 and so we decided to team up.

After some further checking, I came across a paper very similar to LC09 but written 3 years earlier – Forster & Gregory (2006) , hereafter FG06. FG06, however, came to essentially opposite conclusions from LC09, namely that the data implied an overall positive feedback to the earth’s climate system, though the results were somewhat uncertain for various reasons as described in the paper (they attempted a proper error analysis). The big question of course was, how is it that LC09 did not even bother to reference FG06, let alone explain the major differences in their results? Maybe Lindzen & Choi didn’t know about the existence of FG06, but certainly at least one reviewer should have. And if they also didn’t, well then, a very poor choice of reviewers was made.

This became clear when Dr. Wong presented a joint analysis he & I made at the CERES science team meeting held in Fort Collins, Colorado in November. At this meeting, Drs. Trenberth and Fasullo approached us and said they had done much the same thing as we had, and had already submitted a paper to GRL, specifically a comment paper on LC09. This comment was rejected out of hand by GRL, with essentially no reason given. With some more inquiry, it was discovered that:

1. The reviews of LC09 were “extremely favorable”
2. GRL doesn’t like comments and is thinking of doing away with them altogether.
3. GRL wouldn’t accept comments on LC09 (and certainly not multiple comments), and instead it was recommended that the four of us submit a stand-alone paper rather than a comment on LC09.

We all felt strongly that we simply wanted to publish a comment directly on LC09, but gave in to GRL and submitted a stand-alone paper. This is why, for instance, LC09 is not directly referenced in our paper abstract. The implication of statement (1) above is that LC09 basically skated through the peer-review process unchanged, and the selected reviewers had no problems with the paper. This, and for GRL to summarily reject all comments on LC09 appears extremely sketchy.

In my opinion, there is a case to be made on the peer-review process being flawed, at least for certain papers. Many commenters say the system isn’t perfect, but it in general works. I would counter that it certainly could be better. For AGU journals, authors are invited to give a list of proposed reviewers for their paper. When the editor is lazy or tight on time or whatever, they may just use the suggested reviewers, whether or not those reviewers are appropriate for the paper in question. Also, when a comment on a paper is submitted, the comment goes to the editor that accepted the original paper – a clear conflict of interest.

So yes, the system may work most of the time, but LC09 is a clear example that it doesn’t work all of the time. I’m not saying LC09 should have been rejected or wasn’t ultimately worthy of publication, but reviewers should have required major modifications before it was accepted for publication.

To me this raises a number of questions. Why are the editors at GRL apparently not following the published editorial policy on comments? The current policy might not be ideal, and perhaps should be changed, but surely not by fiat, and surely not without announcing that policy change? This particular example has ended up divorcing the response from the original paper and clearly makes it harder to follow the development of this analysis in the literature. Additionally, in cases where there appears to have been lapses in peer-review (for whatever reason), is there not an argument for having a different editor deal with the comment/response? Perhaps a new online journal which independently publishes peer-reviewed comments and responses is called for?

Everyone involved in the peer-review process knows full well the difficulty in finding suitable reviewers who have the time and inclination to do a good review. The pressures on editors both to be seen to be fair, and to actually be fair to the authors (and the readers!) are strong, and occasionally things will go wrong. The measure of such a system is not whether it is perfect, but whether it deals appropriately and quickly with problems when they (inevitably) arise.

NB. Comments on how to improve the situation are welcome, but please avoid simply criticising papers that you personally think shouldn’t have been published in the form they were.

The first published response to Lindzen and Choi (2009) (LC09) has just appeared “in press” (subscription) at GRL. LC09 purported to determine climate sensitivity by examining the response of radiative fluxes at the Top-of-the-Atmosphere (TOA) to ocean temperature changes in the tropics. Their conclusion was that sensitivity was very small, in obvious contradiction to the models.

In their commentary, Trenberth, Fasullo, O’Dell and Wong examine some of the assumptions that were used in LC09’s analysis. In their guest commentary, they go over some of the technical details, and conclude, somewhat forcefully, that the LC09 results were not robust and do not provide any insight into the magnitudes of climate feedbacks.

Coincidentally, there is a related paper (Chung, Yeomans and Soden) also in press (sub. req.) at GRL which also compares the feedbacks in the models to the satellite radiative flux measurements and also comes to the conclusion that the models aren’t doing that badly. They conclude that

In spite of well-known biases of tropospheric temperature and humidity in climate models, comparisons indicate that the intermodel range in the rate of clear-sky radiative damping are small despite large intermodel variability in the mean clear-sky OLR. Moreover, the model-simulated rates of radiative damping are consistent with those obtained from satellite observations and are indicative of a strong positive correlation between temperature and water vapor variations over a broad range of spatiotemporal scales.

It will take a little time to assess the issues that have been raised (and these papers are unlikely to be the last word), but it is worth making a couple of points about the process. First off, LC09 was not a nonsense paper – that is, it didn’t have completely obvious flaws that should have been caught by peer review (unlike say, McLean et al, 2009 or Douglass et al, 2008). Even if it now turns out that the analysis was not robust, it was not that the analysis was not worth trying, and the work being done to re-examine these questions is a useful contributions to the literature – even if the conclusion is that this approach to the analysis is flawed.

More generally, this episode underlines the danger in reading too much into single papers. For papers that appear to go against the mainstream (in either direction), the likelihood is that the conclusions will not stand up for long, but sometimes it takes a while for this to be clear. Research at the cutting edge – where you are pushing the limits of the data or the theory – is like that. If the answers were obvious, we wouldn’t need to do research.

Update: More commentary at DotEarth including a response from Lindzen.

Guest Commentary by John Fasullo, Kevin Trenberth and Chris O’Dell

A recent paper by Lindzen and Choi in GRL (2009) (LC09) purported to demonstrate that climate had a strong negative feedback and that climate models are quite wrong in their relationships between changes in surface temperature and corresponding changes in outgoing radiation escaping to space. This publication has been subject to a considerable amount of hype, for instance apparently “[LC09] has absolutely, convincingly, and irrefutably proven the theory of Anthropogenic Global Warming to be completely false.” and “we now know that the effect of CO2 on temperature is small, we know why it is small, and we know that it is having very little effect on the climate”. Not surprisingly, LC09 has also been highly publicized in various contrarian circles.

Our initial reading of their article had us independently asking, how we could have missed such explicit evidence of the cloud feedback as shown in LC09? Why would such a significant finding have gone undiscovered when these feedbacks are widely studied and recognised as central to the projections of climate change? We discovered these common concerns at a meeting last year and then teamed up to address these questions.

With the hype surrounding the manuscript, one would think that the article provides a sound, rock solid basis for a reduced climate sensitivity. However, our examination of the study’s methods demonstrates that this is not the case. In an article in press (Trenberth et al. 2010 (sub. requ.), hereafter TFOW), we show that LC09 is gravely flawed and its results are wrong on multiple fronts. These are the major issues we found:

• The LC09 results are not robust.

  A goal of LC09 was to quantify the cloud feedback by examining variability in top-of-atmosphere (TOA) radiative fluxes in the tropics as it relates to variability in mean sea surface temperature (SST). To do this they examine only tropical data. In general, they find that during periods of higher-than-normal SST, the radiation emitted and reflected to space by the earth goes up as well, cooling the Earth and amounting to an overall negative climate feedback. To show this, they select intervals of warming and cooling (in a time series of monthly averaged values) and compare fluxes at their endpoints (see Figure). They didn’t provide an objective criterion for selecting these endpoints and in some instances (see their Fig. 1), the selection of these intervals actually appears to be quite odd.

  
  Fig. 1: Warming (red) and cooling (blue) intervals of tropical SST (20°N – 20°S) used by LC09 (solid circles) and an alternative selection proposed derived from an objective approach (open circles) (TFOW, 2010).
  

  The result one obtains in estimating the feedback by this method turns out to be heavily dependent on the endpoints chosen. [edit] In TFOW we show that the apparent relationship is reduced to zero if one chooses to displace the endpoints selected in LC09 by a month or less. So with this method the perceived feedback can be whatever one wishes it to be, and the result obtained by LC09 is actually very unlikely. This is not then really indicative of a robust cloud feedback.

• LC09 misinterpret air-sea interactions in the tropics

  The main changes in tropical SST and radiative fluxes at TOA are associated with El Niño-Southern Oscillation (ENSO) and are not necessarily indicative of forced variability in a closed system. ENSO events cause strong and robust exchanges of energy between the ocean and atmosphere, and tropics and subtropics. Yet LC09 treat the tropical atmosphere as a closed and deterministic system in which variations in clouds are driven solely by SST. In fact, the system is known to be considerably more complex and changes in the flow of energy arise from ocean heat exchange through evaporation, latent heat release in precipitation, and redistribution of that heat through atmospheric winds. These changes can be an order of magnitude larger than variability in TOA fluxes, and their effects are teleconnected globally. It is therefore not possible to quantify the cloud feedback with a purely local analysis.

• More robust methods show no discrepancies between models and observations

  In TFOW, we compute correlations and regressions between tropical SSTs and top-of-atmosphere (TOA) longwave, shortwave and net radiation using a variety of methods. LC09 found the observed behavior to be opposite from that of 11 atmospheric models forced by the same SSTs and conclude that the models display much higher climate sensitivity than is inferred from ERBE. However, in our analysis comparing these relationships with models, we are unable to find any systematic model bias. More importantly, the nature of these relationships in models bears no relationship to simulated sensitivity. That is, the metric developed by LC09 is entirely ineffective as a proxy for simulated sensitivity.

• LC09 have compared observations to models prescribed with incomplete forcings

  The AMIP configuration in the model simulations used by LC09 have incomplete forcings. The AMIP protocol started off a test only of how an atmospheric model reacts to changes in ocean temperatures, and so models often only use the ocean temperature change when doing these kinds of experiments. However, over the period of this comparison, many elements – greenhouse gases, aerosols, the sun and specifically, volcanoes changed the radiative fluxes, and this needs to be taken into account. Some models did this in these experiments, but not all of them.

  For instance, the dominant source of variability in the reflected solar flux arises from aerosols associated with the eruption of Mount Pinatubo in June of 1991 yet all but 2 model simulations examined by LC09 omit such forcings entirely. Other radiative species are absent from the models altogether. It is thus obviously inappropriate to expect such model simulations to replicate observed variability in TOA fluxes.

• LC09 incorrectly compute the climate sensitivity

  By not allowing for the black body radiation (the Planck function) in their feedback parameter, LC09 underestimate climate sensitivity. Using the correct equations, LC09 should obtain a feedback parameter and climate sensitivity of -0.125 and 0.82 K, respectively, rather than their values of -1.1 and 0.5 K.  In contrast, TFOW results yield a positive feedback parameter and greater sensitivity estimate, though we also caution that this approach is not a valid technique for estimating sensitivity, as a closed and therefore global domain is essential (though not by itself sufficient). Lastly, LC09 fail to account for variability in forcings in estimating sensitivity.

While climate models are known to struggle with many aspects of tropical climate, especially in regards to its coupled variability, the problems claimed by LC09 are not among them. Forster and Gregory [2006] and Murphy et al. [2009] address changes in the energy budget with surface temperatures for a much larger domain and present a much more complete and defensible analysis and discussion of issues. They demonstrate that recent observed variability indeed supports a positive shortwave cloud feedback. So the feedbacks from processes other than the Planck function response are clearly positive in both observations and models, in contrast to LC09’s conclusions. Moreover, it is not appropriate to use only tropical SSTs and TOA radiation for feedback analysis as the transports into the extratropics are substantial. Any feedback analysis must also recognize changes in ocean heat storage and atmospheric energy transport into and out of the tropics which are especially large during ENSO events. While the tropics play an important role in determining climate sensitivity, simplistic and arbitrary analyses of tropical variability can be grossly misleading.

References

Forster, P. M. F., and J. M. Gregory (2006), The climate sensitivity and its components diagnosed from Earth Radiation Budget Data, J. Clim., 19, 39–52
Lindzen, R. S., and Y.-S. Choi (2009), On the determination of climate feedbacks from ERBE data, Geophys. Res. Lett., 36, L16705, doi:10.1029/2009GL039628.
Murphy, D. M., S. Solomon, R. W. Portmann, K. H. Rosenlof, P. M. Forster , and T. Wong (2009), An observationally based energy balance for the Earth since 1950, J. Geophys. Res., 114, D17107, doi:10.1029/2009JD012105.
Trenberth, K. E., J. T. Fasullo, Chris O’Dell, and T. Wong, (2010): Relationships between tropical sea surface temperature and top-of-atmosphere radiation. Geophys. Res. Lett., 37, doi:10.1029/2009GL042314, in press.

Gilbert Plass was one of the pioneers of the calculation of how solar and infrared radiation affects climate and climate change. In 1956 he published a series of papers on radiative transfer and the role of CO2, including a relatively ‘pop’ piece in American Scientist. This has just been reprinted (as an abridged version) along with commentaries from James Fleming, a historian of science, and me. Some of the intriguing things about this article are that Plass (writing in 1956 remember) estimates that a doubling of CO2 would cause the planet to warm 3.6ºC, that CO2 levels would rise 30% over the 20th Century and it would warm by about 1ºC over the same period. The relevant numbers from the IPCC AR4 are a climate sensitivity of 2 to 4.5ºC, a CO2 rise of 37% since the pre-industrial and a 1900-2000 trend of around 0.7ºC. He makes a lot of other predictions (about the decrease in CO2 during ice ages, the limits of nuclear power and the like), but it’s worth examining his apparent prescience on these three quantitative issues. Was he prophetic, or lucky, or both?

To understand if Plass should get full credit, we need to see his workings. These are mainly outlined in two more technical papers in Tellus and QJRMS earlier that year. In today’s parlance, Plass calculated the change in top-of-the-atmosphere (TOA) radiative fluxes given a doubling (or a halving) of CO2 while everything else stayed the same. He then took that number and using someone else’s estimate of the sensitivity of the TOA radiation to the surface temperature, he calculated the temperature change that would be necessary to compensate. Converting from the units he used, the radiative flux values for a doubling of CO2 were 8.3 W/m2 and 5.8 W/m2 for clear-sky (no clouds) and averagely cloudy conditions (all-sky) respectively (and slightly larger and of opposite sign for a halving). The sensitivity of the TOA flux to surface temperature he used was around 2.3 W/m2 per ºC (equivalent to a temperature sensitivity of 0.4 ºC/(W/m2)). However, this is a ‘no-feedback’ estimate (allowing only the surface temperature to change with a constant lapse rate, but with no changes to water vapour, albedo or clouds).

Today, our current best guess for the forcing due to 2xCO2 is around 4 W/m2, and the ‘no-feedback’ sensitivity is around 0.3 ºC/(W/m2), giving an expected no-feedback temperature change of about 1.2 ºC, a factor of 3 smaller than the number Plass quoted, though since our number is for ‘all sky’ conditions, it would be a little better to compare it to his averagely cloudy number 2.5 ºC (so a factor of two higher). Note that Plass was a little casual in how he described his numbers and the ‘clear sky’ designation for the 3.6ºC number was not always made clear. However, Plass was well aware that the ‘no-feedback’ case was unrealistic and estimated that the water vapour, cloud and ice-albedo feedbacks would be amplifying, although he was not able to quantify them.

Moving now to the rate of change of CO2 in the atmosphere, Plass made a very good estimate as to how much human emissions of CO2 were increasing. His estimate was (again, in modern units) that then-current emissions were 1.5 GtC based on earlier estimates from Callendar, which actually was an underestimate. Our current best estimate for the anthropogenic emissions in 1956 is about 2.2 GtC. Given the increasing nature of the emissions, Plass then estimated that concentrations would rise about 30% by the end of the 20th Century. This however needs an estimate of how much of the emissions would be absorbed by the oceans and biosphere. Here, Plass has another impressive insight that the ocean chemistry would prevent quick uptake of the human CO2, a concept that wasn’t fully worked out until Revelle and Suess’s paper in 1957 (though possibly he may have been aware of some informal communications earlier). Plass actually assumed that none of the CO2 would be taken up in the short term. So his 30% growth estimate (the actual rise was 36%) was derived from an underestimate in emissions (and emissions growth) combined with an overestimate of the ‘airborne fraction’ (which is roughly 40% of total emissions).

Finally, his estimate of temperature rise of about 1ºC by the end of century follows from the two previous numbers, along with two further assumptions – that the climate is always close to equilibrium with the forcings and that of course, there aren’t any other factors changing. The first assumption affected by the substantial lag in the system because of the thermal inertia of the oceans, and of course, there are many more factors driving climate change over the 20th C. Plass can of course be forgiven for not knowing about the greenhouse impact of rises in CH4, N2O and CFCs (not realised until 1974), or the role of aerosol emissions (1970s), and indeed, he was fortunate that the net effect of all non-CO2 drivers is close to zero (though with significant uncertainties).

So Plass was correct about all of the big issues, but lucky that, in his quantitative estimates, the errors went both ways and end up pretty much cancelling out.

Eli has described this using Isaiah Berlin’s Hedgehog and the Fox metaphor – Plass being the Hedgehog who knows one big thing, and for whom the details are more incidental. I think this is a reasonable take, as long as it is realised that Hedgehogs are not always right, even though in this case he was.

The Fox in this case was another big name in atmospheric physics, Lewis Kaplan. He published a counter to Plass’s 1956 work in Tellus in 1960 (vol. 12, p204-208), and there was a “spirited” exchange of letters in 1961 (vol. 13, p296-302) (references for those of you with libraries – for some reason, none of the old Tellus volumes are online). His calculation used a different methodology, more up-to-date spectra but was different enough in approach and specifics to make a fair apples-to-apples comparison between the results hard to do. Nonetheless, Kaplan declared that “Plass’ estimate of a temperature drop of 3.8ºC due to a halving of [CO2] appears to be too high by a factor of two or three” and that “it would seem, then, that CO2 variations could not play a role in the ice-age cycle unless the changes were by an order of magnitude”.

The subsequent comment and reply are actually very reminiscent of recent disputes in climate science. Plass complains that not enough information was provided to replicate the analysis, that Kaplan used unjustified precision, that he wasn’t comparing like-with-like (all-sky with clear-sky), that he made unjustified technical assumptions, and that his overall conclusion was ‘misleading’ because of the neglected feedbacks (that neither of them had quantified). Kaplan responds that of course there is enough information to check his workings (in another paper), that it was Plass’ fault he compared the all-sky and clear-sky numbers, and that he has exaggerated the impact of the technical criticisms. Notably, Kaplan did not respond on the issue of feedbacks.

Looking over the exchange with a 50 year perspective, a number of things stand out. First, Kaplan does seem to have been closer to modern values in his calculation – Plass was out by a factor of two for the all-sky no-feedback case. I’m not really familiar enough with the details to be be able to tell why (perhaps someone can enlighten us in the comments). However, Kaplan was wrong about everything that has ended up mattering – CO2 does play a big role in ice age cycles (with a magnitude of change close to what Plass anticipated) and its growth today is climatically significant. Significantly, I can find no trace in the literature of any resolution of the technical issues raised in the letters. Resolution in Plass’ favour of the big questions came with further independent efforts as computers got fast enough to do the more complicated feedback problem, better observations, better spectral data and better paleo-climate information (particularly from the ice cores). In some sense, resolution of their technical differences would have been moot because that wasn’t the real issue. Of course, that would have been difficult to see at the time.

So, to summarize, Plass did have some key insights and in many respects was well ahead of his time. But he was also lucky.

Update: Stay tuned, it looks like there is another little wrinkle to this story…

Continuation of the open thread. Please use these threads to bring up things that are creating ‘buzz’ rather than having news items get buried in comment threads on more specific topics. We’ll promote the best responses to the head post.

Knorr (2009): Case in point, Knorr (GRL, 2009) is a study about how much of the human emissions are staying the atmosphere (around 40%) and whether that is detectably changing over time. It does not undermine the fact that CO2 is rising. The confusion in the denialosphere is based on a misunderstanding between ‘airborne fraction of CO2 emissions’ (not changing very much) and ‘CO2 fraction in the air’ (changing very rapidly), led in no small part by a misleading headline (subsequently fixed) on the ScienceDaily news item Update: MT/AH point out the headline came from an AGU press release (Sigh…). SkepticalScience has a good discussion of the details including some other recent work by Le Quéré and colleagues.

Update: Some comments on the John Coleman/KUSI/Joe D’Aleo/E. M. Smith accusations about the temperature records. Their claim is apparently that coastal station absolute temperatures are being used to estimate the current absolute temperatures in mountain regions and that the anomalies there are warm because the coast is warmer than the mountain. This is simply wrong. What is actually done is that temperature anomalies are calculated locally from local baselines, and these anomalies can be interpolated over quite large distances. This is perfectly fine and checkable by looking at the pairwise correlations at the monthly stations between different stations (London-Paris or New York-Cleveland or LA-San Francisco). The second thread in their ‘accusation’ is that the agencies are deleting records, but this just underscores their lack of understanding of where the GHCN data set actually comes from. This is thoroughly discussed in Peterson and Vose (1997) which indicates where the data came from and which data streams give real time updates. The principle one is the CLIMAT updates of monthly mean temperature via the WMO network of reports. These are distributed by the Nat. Met. Services who have decided which stations they choose to produce monthly mean data for (and how it is calculated) and is absolutely nothing to do with NCDC or NASA.

Further Update: NCDC has a good description of their procedures now available, and Zeke Hausfather has a very good explanation of the real issues on the Yale Forum.