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Expert Credibility in Climate Change – Responses to Comments

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Guest commentary by William R. L. Anderegg, Jim Prall, Jacob Harold, Stephen H. Schneider

Note: Before Stephen Schneider’s untimely passing, he and his co-authors were working on a response to the conversation sparked by their recent paper in the Proceedings of the National Academy of Sciences on climate change expertise. One of Dr. Schneider’s final interviews also addresses and discusses many of the issues covered here.

We accept and rely upon the judgment and opinions of experts in many areas of our lives. We seek out lawyers with specific expertise relevant to the situation; we trust the pronouncement of well-trained airplane mechanics that the plane is fit to fly. Indeed, the more technical the subject area, the more we rely on experts. Very few of us have the technical ability or time to read all of the primary literature on each cancer treatment’s biology, outcome probabilities, side-effects, interactions with other treatments, and thus we follow the advice of oncologists. We trust the aggregate knowledge of experts – what do 97% of oncologists think about this cancer treatment – more than that of any single expert. And we recognize the importance of relevant expertise – the opinion of vocal cardiologists matters much less in picking a cancer treatment than does that of oncologists.

Our paper Expert Credibility in Climate Change is predicated on this idea. It presents a broad picture of the landscape of expertise in climate science as a way to synthesize expert opinion for the broader discourse. It is, of course, only a first contribution and, as such, we hope motivates discussion and future research. We encourage follow-up peer-reviewed research, as this is the mark of scientific progress. Nonetheless, some researchers have offered thoughtful critiques about our study and others have grossly mischaracterized the work. Thus, here we provide responses to salient comments raised.
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The Montford Delusion

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Guest commentary by Tamino

Update: Another review of the book has been published by Alistair McIntosh in the Scottish Review of Books (scroll down about 25% through the page to find McIintosh’s review)

Update #2 (8/19/10): The Guardian has now weighed in as well.

If you don’t know much about climate science, or about the details of the controversy over the “hockey stick,” then A. W. Montford’s book The Hockey Stick Illusion: Climategate and the Corruption of Science might persuade you that not only the hockey stick, but all of modern climate science, is a fraud perpetrated by a massive conspiracy of climate scientists and politicians, in order to guarantee an unending supply of research funding and political power. That idea gets planted early, in the 6th paragraph of chapter 1.

The chief focus is the original hockey stick, a reconstruction of past temperature for the northern hemisphere covering the last 600 years by Mike Mann, Ray Bradley, and Malcolm Hughes (1998, Nature, 392, 779, doi:10.1038/33859, available here), hereafter called “MBH98” (the reconstruction was later extended back to a thousand years by Mann et al, 1999, or “MBH99” ). The reconstruction was based on proxy data, most of which are not direct temperature measurements but may be indicative of temperature. To piece together past temperature, MBH98 estimated the relationships between the proxies and observed temperatures in the 20th century, checked the validity of the relationships using observed temperatures in the latter half of the 19th century, then used the relationships to estimate temperatures as far back as 1400. The reconstruction all the way back to the year 1400 used 22 proxy data series, although some of the 22 were combinations of larger numbers of proxy series by a method known as “principal components analysis” (hereafter called “PCA”–see here). For later centuries, even more proxy series were used. The result was that temperatures had risen rapidly in the 20th century compared to the preceding 5 centuries. The sharp “blade” of 20th-century rise compared to the flat “handle” of the 15-19th centuries was reminiscent of a “hockey stick” — giving rise to the name describing temperature history.
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A Eulogy to Stephen Schneider

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We were greatly saddened to learn that our revered colleague Stephen Schneider passed away this morning.

We are posting a personal account by Ben Santer of Steve’s amazing accomplishments and contributions. Ben’s account provides a glimpse into what made Steve so special, and why he will be so deeply missed:

Today the world lost a great man. Professor Stephen Schneider – a climate scientist at Stanford University – passed away while on travel in the United Kingdom.

Stephen Schneider did more than any other individual on the planet to help us realize that human actions have led to global-scale changes in Earth’s climate. Steve was instrumental in focusing scientific, political, and public attention on one of the major challenges facing humanity – the problem of human-caused climate change.

Some climate scientists have exceptional talents in pure research. They love to figure out the inner workings of the climate system. Others have strengths in communicating complex scientific issues to non-specialists. It is rare to find scientists who combine these talents.

Steve Schneider was just such a man.

Steve had the rare gift of being able to explain the complexities of climate science in plain English. He could always find the right story, the right metaphor, the right way of distilling difficult ideas and concepts down to their essence. Through his books, his extensive public speaking, and his many interactions with the media, Steve did for climate science what Carl Sagan did for astronomy.

But Steve was not only the world’s pre-eminent popularizer of climate science. He also made remarkable contributions to our scientific understanding of the nature and causes of climate change. He performed pioneering research on the effects of aerosol particles on climate. This work eventually led to investigation of how planetary cooling might be caused by the aerosol particles arising from large-scale fires generated by a nuclear war. This clear scientific warning of the possible climatic consequences of nuclear war may have nudged our species onto a different – and hopefully more sustainable – pathway.

Steve was also a pioneer in the development and application of the numerical models we now use to study climate change. He and his collaborators employed both simple and complex computer models in early studies of the role of clouds in climate change, and in research on the climatic effects of massive volcanic eruptions. He was one of the first scientists to address what we now call the “signal detection problem” – the problem of determining where we might expect to see the first clear evidence of a human effect on global climate.

After spending many years at the National Center for Atmospheric Research in Boulder, Steve moved to Stanford in 1996. At Stanford, Steve and his wife Terry Root led ground-breaking research on the impacts of human-caused climate change on the distribution and abundance of plant and animal species. More recently, Steve kept intellectual company with some of the world’s leading experts on the economics of climate change, and attempted to estimate the cost of stabilizing our planet’s climate. Until his untimely death, he continued to produce cutting-edge scientific research on such diverse topics as abrupt climate change, policy options for mitigating and adapting to climate change, and whether we can usefully identify levels of planetary temperature increase beyond which we risk “dangerous anthropogenic interference” with the climate system.

Steve Schneider helped the world understand that the burning of fossil fuels had altered the chemistry of Earth’s atmosphere, and that this change in atmospheric composition had led to a discernible human influence on our planet’s climate. He worked tirelessly to bring this message to the attention of fellow scientists, policymakers, and the general public. His voice was clear and consistent, despite serious illness, and despite encountering vocal opposition by powerful forces – individuals who seek to make policy on the basis of wishful thinking and disinformation rather than sound science.

Steve Schneider epitomized scientific courage. He was fearless. The pathway he chose – to be a scientific leader, to be a leader in science communication, and to fully embrace the interdisciplinary nature of the climate change problem – was not an easy pathway. Yet without the courage of leaders like Stephen Schneider, the world would not be on the threshold of agreeing to radically change the way we use energy. We would not be on the verge of a global treaty to limit the emissions of greenhouse gases.

It was a rare privilege to call Steve Schneider my colleague and friend. It was a privilege to listen to Steve jamming on his beloved 12-string guitar; to sing Bob Dylan songs with him. It was a privilege to share laughter, and good food, and a good glass of red wine. It was a privilege to hear his love of science, and his deep passion for it.

We honor the memory of Steve Schneider by continuing to fight for the things he fought for – by continuing to seek clear understanding of the causes and impacts of climate change. We honor Steve by recognizing that communication is a vital part of our job. We honor Steve by taking the time to explain our research findings in plain English. By telling others what we do, why we do it, and why they should care about it. We honor Steve by raising our voices, and by speaking out when powerful “forces of unreason” seek to misrepresent our science. We honor Steve Schneider by caring about the strange and beautiful planet on which we live, by protecting its climate, and by ensuring that our policymakers do not fall asleep at the wheel.

Ben Santer

Revisiting the Younger Dryas

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Guest Commentary by Chris Colose

One of the most intriguing and well-studied climatic events in the past is the Younger Dryas (YD), a rather abrupt climate change between ~12.9 and 11.6 thousand years ago. As the world was slowly warming and ice was retreating from the last glaciation, the YD effectively halted the transition to today’s relatively warm, interglacial conditions in many parts of the world. This event is associated with cold and dry conditions increasing with latitude in the North, temperature and precipitation influences on tropical and boreal wetlands, Siberian-like winters in much of the North Atlantic, weakening of monsoon intensity, and southward displacement of tropical rainfall patterns. RealClimate has previously discussed the YD (here and here) however there have been a number of developments in recent years which deserve further attention, particularly with respect to the spatial characteristics and causes of the YD.
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Information levels

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Rasmus’ recent post on the greenhouse effect raised some interesting points concerning the technical level at which posts or other public communications should be written. This was a relatively technical article as these things go, eschewing the very basic ‘the greenhouse effect is like a blanket’ but not really approaching the level of a technical paper on the subject (no line-by-line calculations for instance). Nonetheless, there were complaints that was too much to be absorbed by the lay public, counter-arguments that making it too simple was patronising, as well as complaints that the discussions were not technical enough (for instance in explaining stratospheric cooling). In these discussions there are clearly the outlines of a common debate, and perhaps a way forward in the future.

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The Muir Russell report

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by Gavin and Mike

The long-awaited and surprisingly thorough Muir Russell report (readable online version) was released this morning. We’ve had a brief read through of the report, but a thorough analysis of this and the supplemental information on the web site will have to wait for a day or so.

The main issue is that they conclude that the rigour and honesty of the CRU scientists is not in doubt. For anyone who knows Phil Jones and his colleagues this comes as no surprise, and we are very pleased to have this proclaimed so vigorously. Secondly, they conclude that none of the emails cast doubt on the integrity and conclusions of the IPCC, again, something we have been saying since the beginning. They also conclude as we did that there was no ‘corruption’ of the peer-review process. Interestingly, they independently analysed the public domain temperature data themselves to ascertain whether the could validate the CRU record. They managed this in two days, somewhat undermining claims that the CRU temperature data was somehow manipulated inappropriately. (Note that this exercise has been undertaken by a number of people since November – all of which show that the CRU results are robust).

All in all, none of the various accusations and insinuations that have been floating around the blogosphere have been sustained. (See some of the early media coverage of the report).

However, there are two issues that have come up that deserve some comment. The first are the evolving practices of data presentation and access, and the second is the issue of how to handle Freedom of Information (FOI) requests.

As climate science has moved away from single researcher/single study/single site analyses towards synthesis across multiple studies, across the globe and involving more and more researchers, practices that were appropriate at one time don’t necessarily scale up to the new environment. Data requests dealt with on an ad-hoc and informal basis work fine if only a couple of people are interested, but more formal and automated procedures are needed when the data sets grow and many more people are involved (see the PCMDI/CMIP3 archive of model results for instance). Given too, the obsession in certain quarters with irrelevant details of smoothing techniques and end-point padding in decade-old papers, it is clear that the more information that is put out as supplementary material to the creation of high-profile figures, the better off we will be. Examples of this for figures in IPCC AR4 already exist, but it will be helpful for IPCC to adopt this practice more generally. Historically, this hasn’t been done – mainly because no-one thought it particularly interesting (most smoothing methods produce very similar results for instance), particularly for figures that weren’t for publication in the technical literature.

One example of this was the cover art on a WMO 1999 report which, until last November, was completely obscure (we are not aware of any mention of this report or this figure before November in any blogospheric discussion, ever). Nonetheless, in the way of these things, this figure is now described as ‘an icon’ in the Muir Russell report (one of their very few mistakes, how can something be an icon if no-one has ever seen it?). In retrospect (and as we stated last year) we agree with the Muir Russell report that the caption and description of the figure could indeed have been clearer, particularly with regard to the way proxy and instrumental data sources were spliced into a single curve, without indicating which was which. The WMO cover figure appears (at least to our knowledge) to be the only instance where that was done. Moving forward, nonetheless, it is advisable that scientists be as clear as possible about what sorts of procedures have gone into the preparation of a figure. But retrospective applications of evolving standards are neither fair nor useful.

With respect to the continuing barrage of FOI requests (which are predominantly for personal communications rather than for data), we can attest from personal experience how disconcerting these can be at first. Since there are no limits on what can be asked for (though there are many limits on what will be delivered), scientists presented with these requests often find them personally invasive and inappropriate. Institutions that do not have much experience with these kinds of requests, and who are not aware of what their employees do that is, and is not, covered by the legislation, are often not much help in sorting out how to respond. This can certainly be improved, as can the awareness of the community of what is recoverable using these procedures. While it is not relevant to the legislation, nor to what can be released, the obvious bad faith of many of the requesters indicates that actual information about the functioning of public bodies is not the primary goal in making these requests. However, it would be a terrible mistake for scientists to retreat from the public discussion on climate science because of these attempts at intimidation.

We will post on more specific aspects of the report, and perhaps the legacy of the whole affair over the next few days…

A simple recipe for GHE

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According to some recent reports (e.g. PlanetArk; The Guardian), the public concern about global warming may be declining. It’s not clear whether this is actually true: a poll conducted by researchers at Stanford suggests otherwise. In any case, the science behind climate change has not changed (also see America’s Climate Choices), but there certainly remains a problem in communicating the science to the public.

This makes me think that perhaps a new simple mental picture of the situation is needed. We can look at climate models, and they tell us what we can expect, but it is also useful to have an idea of why increased greenhouse gas concentrations result in higher surface temperatures. The saying “Everything should be made as simple as possible, but not simpler” has been attributed to Albert Einstein, which also makes me wonder if we – the scientists – need to reiterate the story of climate change in a different way.

Gavin has already discussed this (also see here and here), but it may be necessary to tell story over again, with a slightly different slant. So how can we explain how the greenhouse effect (GHE) work in both simple terms and with a new angle? I also want to explain why the middle atmosphere cools with increasing greenhouse gas concentrations associated with an increased GHE. Here I will try to present a conceptual and comprehensive picture of GHE, explaining both the warming in the lower part of the atmosphere as well as the cooling aloft, and where only the most central features are included. Also, it is important to provide a good background, and we need to start with some very fundamental facts.

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Penn State reports

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The last part of the Penn State inquiry has now reported unanimously that Mike Mann did not engage in any activity that violated scientific norms. Quoting from the report conclusions,

Conclusion of the Investigatory Committee as to whether research misconduct occurred:

The Investigatory Committee, after careful review of all available evidence, determined that there is no substance to the allegation against Dr. Michael E. Mann, Professor, Department of Meteorology, The Pennsylvania State University.

More specifically, the Investigatory Committee determined that Dr. Michael E. Mann did not engage in, nor did he participate in, directly or indirectly, any actions that seriously deviated from accepted practices within the academic community for proposing, conducting, or reporting research, or other scholarly activities.

The decision of the Investigatory Committee was unanimous.

What we said last time….