The first (of three) inquiries on the CRU email affair has reported, and this thread is for discussions of the UK Parliamentary Select Committee report. The conclusions are not un-expected, but there is bound to something for everyone to chew on. Get gnawing!

p.s. there is a useful summary at DeSmogBlog.

We recently ran two articles that were quite critical of aspects of the Guardian’s coverage of the stolen emails. This is a response from Dr. James Randerson, the editor of the Guardian’s environmental website.

I edit the Guardian’s environment website and was part of the editorial team that produced the 12-part investigation by veteran science journalist Fred Pearce into the hacked East Anglia climate emails. I’m very grateful to RealClimate for giving us the opportunity to respond to the recent posts on the investigation: “The Guardian Disappoints” and “Close Encounters of the Absurd Kind”.

I should say first that we hold RealClimate in very high regard. The site is part of the Guardian Environment Network, a collection of more than 20 hand-picked websites including Grist and Nature’s Climate Feedback blog with whom we have a mutual content sharing agreement. Under the arrangement, the Guardian website republishes RealClimate blogs regularly. We take seriously your criticisms and are considering them carefully. The Guardian has a commitment to accuracy and correcting factual errors.

Such is the public interest in this story that ever since the emails were released in November, there has been a strong demand for an in-depth journalistic account of what they tell us about how climate scientists operate. As RealClimate rightly pointed out, the response from much of the media has been lazy to the point of “pathology”.

No other media organisation has come close to producing such a comprehensive and carefully researched attempt to get to the bottom of the emails affair. The investigation tries to reflect the complexity and historical context of the story, and runs to some 28,000 words – of which around half appeared in the printed newspaper.

Dr. Schmidt did not mince his words though when he said that Fred’s investigation falls, “well below the normal Guardian standards of reporting”, while Dr Ben Santer wrote, “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.” Both have also criticised our experimental online exercise to harness the expertise of people with a special knowledge of the emails in order to create a “peer reviewed” account of what they tell us.

More on that later, but it is wrong to suggest that this is a lazy substitute for traditional journalistic standards and that key protagonists were not invited to respond prior to publication. On the contrary, the investigation was subject to rigorous editorial checking and Fred contacted numerous individuals in the course of his research. Many (particularly those at UEA) declined to comment.

The other side of the story

The RealClimate commentary reads like a distorted fairground mirror of the Guardian investigation – one that highlights the uncomfortable bits but blurs the rest. The posts did point out that “Some of the other pieces in this series are fine” but do not reflect the large amount of analysis in the investigation of the way the emails have been misused by those with a political agenda and the extensive context we included to indicate the pressure scientists writing those emails were under from time-consuming requests for data.

In part 2 (How the ‘climategate’ scandal is bogus and based on climate sceptics’ lies), for example, we detail how the “hide the decline” email has been misused by Sarah Palin, Senator James Inhofe and others to create, apparently deliberately, the impression that climate scientists had fiddled the figures.

Almost all the media and political discussion about the hacked climate emails has been based on soundbites publicised by professional sceptics and their blogs. In many cases, these have been taken out of context and twisted to mean something they were never intended to.

In part 1 (Battle over climate data turned into war between scientists and sceptics) and in a separate piece that appeared in the newspaper (Climate scientists have long been targets for sceptics) Fred outlines the tactics and motivations of some on the “sceptic” side of the debate.

All this happened against the backdrop of a long-term assault by politically motivated, and commercially funded, climate-change deniers against the activities of many of the key scientists featuring in the emails.

Similarly in Part 7 (Victory for openness as IPCC climate scientist opens up lab doors) Fred explains how the emails give a special insight into what being on the end of that assault was like.

In the leaked emails, [Ben Santer] is seen sharing those experiences with other victims of hectoring and abuse by the more rabid climate sceptics. Others had their own horror stories, including Mike Mann over his hockey stick graph, Kevin Trenberth over his analysis of hurricanes and warming in the aftermath of Katrina, and later Jones over his escalating data wars. In each case, they argue, legitimate debates about scientific analysis and access to researchers’ data have been turned into vindictive character assassination.

And in the concluding part of the investigation (Part 12: Climate science emails cannot destroy argument that world is warming, and humans are responsible), Fred lays out unequivocally that nothing in the emails casts doubt on the case for climate change being attributable to human actions.

Is the science of climate change fatally flawed by the climategate revelations? Absolutely not. Nothing uncovered in the emails destroys the argument that humans are warming the planet. None of the 1,073 emails plus 3,587 files containing documents, raw data and computer code upsets the 200-year-old science behind the “greenhouse effect” of gases such as carbon dioxide, which traps solar heat and warms the atmosphere. Nothing changes the fact that carbon dioxide is accumulating in the atmosphere thanks to human emissions from burning carbon-based fuels such as coal and oil. Nor the calculations by physicists that for every square metre of the Earth’s surface, 1.6 watts more energy enters the atmosphere than leaves it.

And we know the world is warming as a result. Thousands of thermometers in areas remote from any conceivable local urban influences tell us that. The oceans are warming too. The great majority of the world’s glaciers are retreating, Arctic sea ice is disappearing, sea levels are rising ever faster, trees are climbing up hillsides and permafrost is melting.

These are not statistical artefacts or the result of scientists cherry-picking data.

Looking under every rock

There are few, if any newspapers in the world with a stronger commitment to action on climate change than the Guardian and our sister paper the Observer. We have a team of 6 full-time environment correspondents as well as three editors and a collection of bloggers and columnists.

It was the Guardian that orchestrated a global editorial carried by 56 newspapers in 45 countries on 7th December 2009 to call for action from world leaders at Copenhagen. [RC: Also at RealClimate]

And we have been instrumental in supporting the 10:10 climate change campaign which aims to inspire individuals, organisations and businesses to cut their carbon emissions by 10% in 2010. The UK branch of 10:10 has signed up nearly 60,000 people and over 4000 businesses and organisations.

But only by looking thoroughly under every rock can those of us pressing for action on climate change maintain with confidence that the scientific case remains sound. Fred’s investigation shows that confidence is indeed well placed, but to claim that the emails do not throw up some troubling issues looks like the inward-looking mentality that is sometimes (perhaps understandably) expressed in the emails themselves.

The two posts published so far on RealClimate come to over 8500 words and it has been suggested that a line by line response to each of the points made would not be productive. I say again that we are totally unembarrassed about correcting genuine errors, but many of the points raised at RealClimate are differences of interpretation. There were implications that the investigation omitted some key information which in fact appeared in Fred’s pieces – for example that the data on Chinese weather station locations from the Phil Jones et al 1990 Nature data were eventually released publicly and that the two studies Jones had threatened to keep out of the IPCC AR4 report were in fact cited there.

However, I would like to make four points:

• Dr Phil Jones, the head of the Climatic Research Unit at UEA has said in an interview with Nature that the handling of the records of the Chinese weather station data from his 1990 Nature paper (which Fred wrote about in part 5 of the investigation) was “not acceptable… [it's] not best practice,” and he acknowledged that that stations “probably did move”. He added that he was considering a correction to Nature. To our knowledge, no other media organisation or blogger had used the emails to shed light on the controversy over the 1990 paper so a correction would not be on the table without the Pearce investigation.
• Dr. Schmidt states that we imply Dr Tom Wigley supported allegations of “fabrication” from climate sceptic Douglas Keenan. We do not make that assertion in the piece. Also, Dr Schmidt does not reproduce the most eye-catching quotes from a May 2009 email from Wigley to Jones in which he raises serious doubts about the quality of Jones’s scientific team and his handling of the Chinese weather station data.The hacked emails do not include a response from Jones if there was one.
• As Dr. Schmidt pointed out, we have made three small corrections to the piece “Controversy behind climate science’s ‘hockey stick’ graph” at the request of Dr Michael Mann, but none changed the main point the article was making, which was that in 1999, Mann’s hockey-stick reconstruction was the subject of intense academic debate amongst climate scientists.
• Neither of the RealClimate blogs dealt with Fred’s piece on FOI requests, but a statement from the UK’s deputy information commissioner Graham Smith has made clear that he believes that FOI legislation was not followed correctly. He wrote, “The emails which are now public reveal that [climate sceptic David] Holland’s requests under the Freedom of Information Act were not dealt with as they should have been under the legislation. Section 77 of the Freedom of Information Act makes it an offence for public authorities to act so as to prevent intentionally the disclosure of requested information.” This is a serious issue worthy of discussion and debate.

Peer-reviewed journalism

I mentioned above our attempt to create a definitive account of the emails by leveraging the expertise of people involved or with a special knowledge of the messages and the issues they discuss. This account will eventually be expanded into a book. In practice, this means us adding annotations from people to the online versions of the articles so that readers can watch a form of living peer-review in progress. Click on the yellow highlights in the pieces themselves to read the annotations.

This represents an extraordinary commitment to transparency that we believe is unique in journalism. What other news organisation would open itself to direct criticism in this way including, for example, annotations that read “this is absolutely false” and “this is really bad”? The respected Columbia Journalism Review has praised the approach. “Regardless of whether you agree with Pearce or Schmidt, the Guardian’s approach appropriately acknowledges that evidence leaves room for some degree of interpretation. It is this kind of detailed, intellectually honest (even technologically innovative) reporting that news outlets like The New York Times should be striving for,” it wrote.

In the same spirit we have showcased diverse critical opinions on the issues and our own coverage of them, including from Dr Myles Allen, Dr Vicky Pope, Dr Mike Hulme and the Guardian’s environment correspondent Dr David Adam. Again few newspapers would have reflected such diverse viewpoints.

The reaction from some to our online annotation exercise has been hostile though. On our letters pages Dr Myles Allen and Dr Ben Santer wrote last week:

Claiming to produce “the definitive” analysis now is a brazen attempt to pre-empt the inquiries’ conclusions…What is wrong with the old-fashioned approach of checking facts before publication? When the final version is published, you will no doubt make much of the fact that “everyone had a chance to comment”, implying that any statement that was not challenged must therefore be true.

Our intention is not to undermine or pre-empt the ongoing inquiries into the CRU emails. Each of those has a very specific remit and none is attempting to produce a detailed account that uses the emails to shed light on recent climate controversies. Nor is this an exercise in blackmailing scientists into fact-checking on the cheap – if it were then it would be a monumental false-economy.

In truth, this is a serious-minded attempt to make sense of a large volume of new information about a complex and highly charged issue. No other newspaper has ever offered its journalism up for very public and exacting scrutiny in this way. We sincerely invite those involved who know the issues most thoroughly to contribute.

In a recent post here at RealClimate, Simon Lewis wrote regarding a 2010 paper by Samanta et al. on the effect of single-year drought conditions on the Amazon. Samanta et al. claimed to have contradicted a 2007 paper by Scott Saleska et al., and to have thereby overturned some IPCC conclusions.

Here is Saleska’s commentary in full
——-
Guest Commentary by Scott Saleska, University of Arizona

The title of the Lewis post (“Up is Down, Brown is Green”) is perhaps even more true than the insightful commentary by my colleague Simon Lewis indicates! The Samanta et al paper says brown, but in fact their own data (when you dig it out of the supplement) shows green, consistent with (and indeed virtually indistinguishable from) our original findings published in Science (Saleska et al., 2007).

Samanta et al. misrepresents our work on many levels (one of which is to assert, falsely, that we did not filter out atmosphere-corrupted observations when in fact we did), and we intend, of course, to present an appropriate response in the peer reviewed literature, where the technical details of our differences may be evaluated by anyone who wishes. But for the moment we will, for the sake of argument, accept their analysis at face value and ask: even if Samanta et al. are 100% correct in their critique of our methods (which we of course dispute), what are the implications? Does the alternative to our method which Samanta et al. advocate, or the recent update in the MODIS satellite data (to version 5 from version 4), make any difference for the main conclusion of our paper? With due respect to our friends and colleagues at Boston University, the answer is no, it does not.

First: the actual relevant Samanta et al data (which comes from their Supplement, Table S3) is this:

Note that the green area in the drought region increases to its maximum (10.8% of the total area = 10.8/33.68 = 32% of the valid area) in 2005. In other words, the Samanta et al data contradict the Samanta et al text and title (which states that Amazon forests did not green up): not only do forests in the drought region green up, they green up alot, more than any other year since the MODIS satellite sensor was launched.

Second, how does this compare to Saleska et al. (2007), which Samanta et al claim to rebut? Here are the numbers (again, taken directly from Samanta et al, Table S3 and Saleska et al., 2007):

Fraction of valid pixels in the 2005 drought region that are “green” (> + 1 Standard deviation)
Saleska et al. (2007): 34% (p<0.000001)
Samanta et al. (2010): 32% (p<0.004)

The bottom line is that their observed 2005 result (32% greenness) is indistinguishable from ours (34%). I.e. Samanta et al effectively reproduce the results of Saleska et al.

This summary response, of course, begs some very interesting questions about tropical forest function under climatic variability and change (indeed the most interesting questions of all!): what caused the anomalously disproportionate green-up in the drought region? And, even if satellite “green up” does in fact represent an increase in photosynthesis (as we think), could this in fact be a symptom of the trees compensating for the increased stress of the drought? The bottom line “carbon balance” of a tree depends on both photosynthetic uptake and respiratory losses, and it is almost certainly the case that those losses (which were not seen by the satellite) increased under the hotter and drier conditions of the drought as well.

Thus, the most intriguing idea to me is that the short-term satellite-detected green-up, and the longer term increase in net carbon loss reported in the Phillips et al paper (discussed by Simon Lewis) are not in conflict at all. It might well be that they represent different parts of a coherent forest response to drought, in which the longer term losses are larger than the satellite-detected attempt to compensate for them by increasing photosynthesis, and in the end, increased tree mortality is the result.

In conclusion I would like to reinforce Simon’s point about Samanta et al and the IPCC. More important than whatever they say about our one short paper, Samanta et al. truly and egregiously misrepresent the implications, of both their work and ours, when they claim that a single paper on short term vegetation response somehow rebuts the IPCC’s review of the large scientific literature on how Amazonia might respond to long-term shifts in the mean climate state. It is an illogical and misguided claim on many levels, one that is already and deservedly attracting the opprobrium of many of my colleagues, talented scientists who study Amazon forests and climate (see Scientists speak: Amazon “myths” are not debunked).

In sum:

– Samanta et al data show a drought region green up that is on average indistinguishable from Saleska et al (but they call it NO green up).
– Samanta et al data almost exactly reproduce Saleska et al’s most salient bottom-line result (but they say what we did was not reproducible).
– the Samanta et al paper, based on a three-month drought response, says not one word about long-term climate change scenarios reviewed in IPCC (but they advertise their analysis as “reject[ing] claims” put forward by the IPCC).

Another open thread. OT comments from the Amazon drying thread have been moved over. As usual, substantive comments only please and no abuse.

In the alternate universe of Fox News, Anthony Watts, and many others, up is down. Now, it appears, brown is green. Following the total confusion over the retraction of a paper on sea level, claims of another “mistake” by the IPCC are making the rounds of the blogosphere. This time, the issue is the impact of rainfall changes on the Amazon rainforest.

A study in 2007 showed that the forest gets greener when it rains less. A new study, by Samanta et al. in Geophysical Research Letters shows that the earlier work was flawed. Aided by an apparently rather careless press release, this is being used as evidence that the Amazon is less sensitive to rainfall changes than the IPCC claimed. But the Samanta et al. paper actually does not address the central questions at all. It only addresses whether a single anomalous rainfall year had an impact that is measureable and interpretable from a satellite sensor. The conclusion is that they could not detect a change. As noted in a commentary from Simon Lewis, University of Leeds, “the critical question is how these forests respond to repeated droughts, not merely single-year droughts.”

Lewis – a broadly published expert on tropical forests – makes a number of additional important points in his commentary below. Bottom line: IPCC gets it right as usual.

—————
Guest Commentary by Simon Lewis, University of Leeds, UK

The new Samanta et al. study uses sensors on satellites to assess the colour of the rainforest canopy in the dry season of the year 2005, compared to the dry seasons of the years 2003 and 2004. More detected green colour in 2005 may suggest that the forest is being more productive (more green leaves photosynthesising), or more brown colours may suggest leaves dying and less productivity, than the previous years. The results show that 2005 was little different to the previous years, despite the strong drought.

This is important new information, as in 2007, a paper using broadly the same satellite-based method showed a strong ‘greening-up’ of the Amazon in 2005, suggesting tolerance to drought (Saleska et al. 2007, Science). The new study shows that those results were not reproducible, but also highlight the extreme caution that should be attached to satellite studies generally in this field, with instruments in space collecting data which is then used to infer subtle changes in the ecology of tropical forests.

In contrast to the 2007 paper, Oliver Phillips, myself, and others, published a paper in Science last year, using ground observations from across the Amazon, showing that while the 2005 drought did not dramatically change the growth of the trees compared to a normal year, as Samanta et al. also show, the deaths of trees did increase considerably. The new study of Samanta et al. does not contradict the Phillips et al. study, which itself shows the Amazon is vulnerable to drought via impacts on tree mortality. The Phillips et al. paper showed that remaining Amazon forest trees changed from absorbing nearly 2 billion tonnes of CO₂ from the atmosphere annually over recent decades, as tree growth has been exceeding mortality, to being a large, but temporary, source of over 3 billion tonnes, from the elevated tree mortality associated with the 2005 drought event.

The evidence for the possibility of a major die-back of the Amazon rainforest is due to two factors,

1. That climate change induced decreases in rainfall in the dry season occur, and

2. The trees cannot tolerate these reductions in rainfall.

The Samanta paper does not directly address the first point; this is addressed using global circulation models (of which some, but not all, show a strong drying trend for the east of the Amazon over the 21st century). The second point is only addressed in a limited way. The critical question is how these forests respond to repeated droughts, not merely single-year droughts. The forests are of course able to withstand these single droughts (otherwise there would be no rainforest!) — it is their ability to survive an increased frequency of the most severe droughts that is critical to answer. Drought experiments, where a roof is built under the forest canopy to reduce rainfall, show that most forest trees survive a single year’s intense drought, in agreement with the ground observations in the 2005 drought, but can’t persist with repeated years of drought. The Samanta study does not address this point at all.

In conclusion, the new Samanta et al. study lends further weight to the emerging picture of the impact of the 2005 drought: that tree growth was relatively unaffected, but tree mortality increased, contributing temporarily to accelerating the rate of climate change, rather than as usual reducing it, via additions of carbon to the atmosphere from the dead trees. The mortality was far from catastrophic, but the impact on the carbon cycle was globally significant. This is hardly the ‘no impact’ of the 2005-drought on the forest suggested in various news reports.

I should add that there is considerable uncertainty associated with the models suggesting decreases in rainfall, and uncertainty as to how Amazon forests may react (especially when one considers the impacts of deforestation, logging, and fire combined with climate change impacts). But this uncertainty is being chipped away at by scientists, a task in which the Samanta et al. paper assists.

Oddly, the Boston University press release to accompany the paper was titled, “New study debunks myths about Amazon rain forests”. The opening line runs: “A new NASA-funded study has concluded that Amazon rain forests were remarkably unaffected in the face of once-in-a-century drought in 2005, neither dying nor thriving, contrary to a previously published report and claims by the Intergovernmental Panel on Climate Change.” So, have scientists, myself included, been peddling myths? Have respected journals being publishing them? Have the IPCC? The answer is no, no and no.

The reality is that the IPCC have largely ignored the papers on the model results of decreasing rainfall in the east of the Amazon, and the diverse evidence used to assess the sensitivity of these forests to such rainfall reductions. There are a couple of lines in IPCC Working Group I (“New coupled climate-carbon models (Betts et al., 2004; Huntingford et al., 2004) demonstrate the possibility of large feedbacks between future climate change and vegetation change, discussed further in Section 7.3.5 (i.e., a die back of Amazon vegetation and reductions in Amazon precipitation).”). And in Working Group II there is a now infamous single sentence:

“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).”

The statement is not as carefully worded as it should be, and incorrectly referenced, but basically scientifically correct and defensible with recourse to the peer-reviewed literature available at the time. Rainforest persists above a threshold of rainfall, below which one finds savanna. If this threshold is crossed a landscape dominated by rainforest can ‘flip’ to savanna. Therefore a ’slight’ reduction can lead to a ‘dramatic’ reaction. Of course, evidence of a shift to a new lower rainfall climate regime is needed, and evidence of large areas of forest close to that rainfall threshold would be required for the IPCC statement to be reasonable; there is ample published evidence for both.

Overall the conclusions in the IPCC 2007 Fourth Assessment Report are strengthened (because the anomalous result of the Saleska et al. 2007 paper appear to be at fault), not weakened, by the new Samanta et al. study as their press release implies.

Update: Saleska responds, pointing out that a) their 2007 paper is not contradicted by Samanta et al. (2010); b) nor is the IPCC report weakened by either paper. Confused? Then read what he has to say: here.

Another Perspective (pdf), by Shuo Zhang.

Inequality, development, and obesity: just a few reasons why the global public-health message is so
important for the change to a low carbon future.

A letter from a reader (reproduced with permission):

Dear RealClimate team:

I have a background in biology and studied at post-grad level in the area of philosophy of science. For the last few years, I have been working on a book about the logic of argument used in debates between creationists and evolutionists.

About a year ago I decided it was time to properly educate myself about climate science. Being perhaps a little too influenced by Harry M Collins’ “The Golem” (and probably too much modern French philosophy!), I was definitely predisposed to see group-think, political and cultural bias in the work of climatologists.

On the whole, though, I tried hard to follow the principles of genuine skepticism, as I understood them.

Obviously, there are plenty of ill-considered opinions to be found either side of any issue, but only the most ignorant person could fail to see the terrible intellectual gulf between the quality of so-called skeptic sites and those defending the science behind the AGW thesis.

What convinced me, though, is that the arguments made by a few sites like yours are explicit and testable. In particular, it is useful that RealClimate sticks to the science as much as possible. It has been a lot of hard work to get here, but I am now at a point where I understand the fundamentals of climate science well enough to articulate them to others.

For my part, I am grateful to you guys. I hope it gives you some small amount of satisfaction to know that your work can convert readers who really were skeptics in the beginning. I use the word ’skeptic’ carefully – the one thing most commonly absent from the so-called ’skeptics’ is authentic skepticism.

By the way, my book is an attempt to categorise the various logical errors people fall into when they search for arguments to support a conclusion to which they have arrived at a priori. It will now have a few chapters on global warming.

All the best,

Imagine this. In its latest report, the IPCC has predicted up to 3 meters of sea level rise by the end of this century. But “climate sceptics” websites were quick to reveal a few problems (or “tricks”, as they called it).

First, although the temperature scenarios of IPCC project a maximum warming of 6.4 ºC (Table SPM3), the upper limit of sea level rise has been computed assuming a warming of 7.6 ºC. Second, the IPCC chose to compute sea level rise up to the year 2105 rather than 2100 – just to add that extra bit of alarmism. Worse, the IPCC report shows that over the past 40 years, sea level has in fact risen 50% less than predicted by its models – yet these same models are used uncorrected to predict the future! And finally, the future projections assume a massive ice sheet decay which is rather at odds with past ice sheet behaviour.

Some scientists within IPCC warned early that all this could lead to a credibility problem, but the IPCC decided to go ahead anyway.

Now, the blogosphere and their great media amplifiers are up in arms. Heads must roll!

Unthinkable? Indeed. I am convinced that IPCC would never have done this.

The North Sea (see Stefan’s photostream on Flickr)

But here is what actually did happen.

In its latest report, the IPCC has predicted up to 59 cm of sea level rise by the end of this century. But realclimate soon revealed a few problems.

First, although the temperature scenarios of IPCC project a maximum warming of 6.4 ºC (Table SPM3), the upper limit of sea level rise has been computed for a warming of only 5.2 ºC – which reduced the estimate by about 15 cm. Second, the IPCC chose to compute sea level rise up to the year 2095 rather than 2100 – just to cut off another 5 cm. Worse, the IPCC report shows that over the past 40 years, sea level has in fact risen 50% more than predicted by its models – yet these same models are used uncorrected to predict the future! And finally, the future projections assume that the Antarctic ice sheet gains mass, thus lowering sea level, rather at odds with past ice sheet behaviour.**

Some scientists within IPCC warned early that all this could lead to a credibility problem, but the IPCC decided to go ahead anyway.

Nobody cared about this.

I mention this because there is a lesson in it. IPCC would never have published an implausibly high 3 meter upper limit like this, but it did not hesitate with the implausibly low 59 cm. That is because within the IPCC culture, being “alarmist” is bad and being “conservative” (i.e. underestimating the potential severity of things) is good.

Note that this culture is the opposite of “erring on the safe side” (assuming it is better to have overestimated the problem and made the transition to a low-carbon society a little earlier than needed, rather than to have underestimated it and sunk coastal cities and entire island nations). Just to avoid any misunderstandings here: I am squarely against exaggerating climate change to “err on the safe side”. I am deeply convinced that scientists must avoid erring on any side, they must always give the most balanced assessment they are capable of (and that is why I have often spoken up against “alarmist” exaggeration of climate science, see e.g. here and here).

Why do I find this IPCC problem far worse than the Himalaya error? Because it is not a slip-up by a Working Group 2 author who failed to properly follow procedures and cited an unreliable source. Rather, this is the result of intensive deliberations by Working Group 1 climate experts. Unlike the Himalaya mistake, this is one of the central predictions of IPCC, prominently discussed in the Summary for Policy Makers. What went wrong in this case needs to be carefully looked at when considering future improvements to the IPCC process.

And let’s see whether we learn another lesson here, this time about society and the media. Will this evidence for an underestimation of the climate problem by IPCC, presented by an IPCC lead author who studies sea level, be just as widely reported and discussed as, say, faulty claims by a blogger about “Amazongate”?

p.s. Recent sea level results. A number of broadly based assessments have appeared since the last IPCC report, which all conclude that global sea level rise by the year 2100 could exceed one meter: The assessment of the Dutch Delta Commission, the Synthesis Report of the Copenhagen Climate Congress, the Copenhagen Diagnosis report as well as the SCAR report on Antarctic Climate Change. This is also the conclusion of a number of recent peer-reviewed papers: Rahmstorf 2007, Horton et al. 2008, Pfeffer et al. 2008, Grinsted et al. 2009, Vermeer and Rahmstorf 2009, Jevrejeva et al. 2010 (in press with GRL). The notable exception – Siddall et al. 2009 – was withdrawn by its authors after we revealed numerical errors on Realclimate. This is a good example of self-correction in science (in stark contrast with the climate sceptics’ practice of endlessly perpetuating false information). Rather bizarrely, Fox News managed to turn this into the headline “More Questions About Validity of Global Warming Theory“.

** About the numbers stated above. Regarding the actual IPCC AR4 numbers, adjust the IPCC upper estimate of 59 cm by adding 15 cm to make it apply to 6.4 ºC warming (not just 5.2 ºC) and 5 cm to make it go up to 2100 (not just 2095). That gives you 79 cm. Add 50% to adjust for the underestimation of past sea level rise and you get 119 cm.
For the hypothetical case at the start of this post, just introduce similar errors in the other direction. Let’s add 31 cm by going up to 7.6 ºC and the year 2105 (in fact that is “conservative” but it gives a nice round number, 150 cm). Now assume you have a model compared to which actual sea level is rising 50% slower (rather 50% faster): now you’re at the 3 meters mentioned above. For details, see The IPCC sea level numbers.

Here are the Cambridge Zero Carbon Society Accounts for 2008/9

Here are the final, summary  Cambridge Climate Summit 2008 Accounts and the cancelled Cambridge Climate Conference 2009 Accounts

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!