Cold comfort for ‘sceptics’ in Antarctic research

The front cover of the 19 February 2011 edition of The Spectator magazine trumpeted an article with two headlines ‘The truth about the Antarctic: What global warming activists don’t want you to know’ and ‘The ice storm: Nicholas Lewis and Matt Ridley expose the bias and bluster behind the latest shaky global warming data’.

Over two pages inside the magazine, the authors laid out their case to justify the front page splash. But as we have come to expect from The Spectator when it comes to climate change, the article was simply an exercise in biased rhetoric.

At the heart of the magazine’s tale is a row between the authors of two academic journal papers which use different statistical techniques to interpret temperature trends for Antarctica over the past 50 years.

One paper is ‘Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year‘ by Eric Steig and co-authors, which was published by Nature in January 2009.

The other paper is ‘Improved methods for PCA-based reconstructions: case study using the Steig et al. 2009 Antarctic temperature reconstruction‘, by Ryan O’Donnell and co-authors, which was published in the Journal of Climate in December 2010.

The paper by Steig and co-authors concluded that there had been an overall warming of the continent of Antarctica over the past 50 years. This was considered to be a significant finding because most previous studies have shown strong warming on the Antarctic Peninsula but mixed trends elsewhere, particularly for the past 30 years. Warming has been detected across every other continent, and the mixed trends for Antarctica, which are thought to result from changes in atmospheric circulation, have been seized on by ‘sceptics ‘. But previous research has highlighted the shortage of long-term temperature data for much of Antarctica.

Essentially, Steig and co-authors applied a new statistical method to combine the few long-term temperature records from weather stations on Antarctica with the shorter recent records from satellite measurements (which themselves have some serious limitations). The paper concluded that there had been “significant warming” over most of West Antarctica, and that “the continent-wide average near-surface temperature trend is positive”.

The paper by O’Donnell and co-authors was prepared by a number of self-proclaimed climate change ‘sceptics’ who use blogs to comment on journal papers and other information. One of the co-authors is Steve McIntyre, who runs the Climate Audit website, and who was one of the main protagonists in the row over the so-called ‘hockey stick’ graphs of global temperature. The paper by O’Donnell and co-authors represented the culmination of a series of blog postings which attacked the methods and conclusions of the paper by Steig and co-authors. It is to be welcomed that O’Donnell and his co-authors have chosen to submit their analysis to scrutiny through the peer review process in the same way that mainstream researchers do, rather than just adding to the morass of inaccurate and misleading claims on blogs.

O’Donnell and co-authors were critical of the way in which Steig and co-authors applied their statistical methods to the Antarctic data. They applied alternative statistical techniques to carry out their own analysis and reached some different results – they showed much stronger warming on the Antarctic Peninsula, but less warming across the rest of the continent, and some cooling in a few places. It is perhaps worth re-reading the abstract of the paper by O’Donnell and co-authors, particularly the second half, to appreciate how their results differed from those of Steig and co-authors:

“A detailed analysis is presented of a recently published Antarctic temperature reconstruction that combines satellite and ground information using a regularized expectation-maximization algorithm. Though the general reconstruction concept has merit, it is susceptible to spurious results for both temperature trends and patterns. The deficiencies include: (a) improper calibration of satellite data; (b) improper determination of spatial structure during infilling; and (c) suboptimal determination of regularization parameters, particularly with respect to satellite principal component retention. We propose two methods to resolve these issues. One utilizes temporal relationships between the satellite and ground data; the other combines ground data with only the spatial component of the satellite data. Both improved methods yield similar results that disagree with the previous method in several aspects. Rather than finding warming concentrated in West Antarctica, we find warming over the period of 1957–2006 to be concentrated in the Peninsula (≈0.35°C decade−1). We also show average trends for the continent, East Antarctica, and West Antarctica that are half or less than that found using the unimproved method. Notably, though we find warming in West Antarctica to be smaller in magnitude, we find that statistically significant warming extends at least as far as Marie Byrd Land. We also find differences in the seasonal patterns of temperature change, with winter and fall showing the largest differences and spring and summer showing negligible differences outside of the Peninsula.”

Steig has described the paper by O’Donnell and co-authors as “a perfectly acceptable addition to the literature”, even though he does not agree with all of the findings.

The story in The Spectator was co-written by Nicholas Lewis, one of the co-authors on the paper with O’Donnell, and Matt Ridley, a zoologist who has written some very popular books on evolutionary biology. Ridley’s previous writings on climate change have been aggressively ‘sceptical’, including an article in The Spectator which wrongly alleged that the emails hacked from the Climatic Research Unit at the University of East Anglia had shown “the exaggerations, distortions and corruptions in the climate establishment”. It is perhaps not surprising that Dr Ridley is a member of the “academic advisory council” of Lord Lawson’s ‘sceptic’ lobby group, the Global Warming Policy Foundation.

The article by Ridley and Lewis displays the bias that might be expected from those on one side of this argument. Much of the article is devoted to a one-sided complaint about the peer review process for the paper by O’Donnell and co-authors – Ridley and Lewis are apparently unhappy that Steig was one of the four referees who reviewed the paper for the journal and that he was so critical of it.

Whilst Ridley and Lewis try to give the impression that something untoward took place, the process appears fairly unremarkable by the usual standards of academic peer review for most subjects. Certainly there are challenges in inviting a researcher to referee a paper that is critical of his own work, but it is not unheard of, particularly for an area in which there are relatively few experts. And, of course, the review editor for the journal ultimately controlled the process and decided to what extent the authors of the submitted paper needed to respond to the criticisms of the referees in order to make it acceptable for publication.

In that respect, it is worth recalling Appendix 5 of the report of the ‘Independent Climate Change E-mails Review’ (starting on page 126), by Richard Horton, the editor of the medical journal The Lancet – it includes the following section )PDF):

“Are reviewers objective in their judgments? Pure objectivity is impossible. For some subjects, an editor can predict the judgment of the reviewer based on past experience with that reviewer. But this misses the point of what an editor is seeking. It is not simply the judgment of reject/accept that an editor wants from a reviewer. That decision is the responsibility of the editor and the editor alone. What an editor really seeks is a powerful critique of the manuscript – testing each assumption, probing every method, questioning all results, and sceptically challenging interpretations and conclusions. Armed with that critique, the editors decide – and take full responsibility for deciding.”

There is a lot of rhetoric and bias in the article by Ridley and Lewis, particularly where they try to draw links with the controversy over the emails hacked from the University of East Anglia. For instance, they repeat this claim made many times previously by self-proclaimed ‘sceptics’:

“Hard evidence of such obstruction first came to light in the now infamous ‘Climategate’ emails from the University of East Anglia, which included this gem from climatologist PhilJones: ‘The other paper by [Ross] M[cKitrick] and [Pat] M[ichaels] is just garbage… I can’t see either of these papers being in the next IPCC report. Kevin [Trenberth] and I will keep them out somehow — even if we have to redefine what the peer-review literature is!’ The paper in question pointed out that regional temperature rises correlated with economic development, implying they were contaminated by local urban warming unrelated to greenhouse gases.”

What the article by Ridley and Lewis conveniently neglects to mention is that the paper by McKitrick and Michaels was reviewed and explicitly mentioned in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, so this alleged ‘smoking gun’ lacks a victim!

The article in The Spectator by Ridley and Lewis also includes a number of statements that are inaccurate and misleading, including:

“Papers that come to lukewarm or sceptical conclusions are published, if at all, only after the insertion of catechistic sentences to assert their adherence to orthodoxy. Last year, a paper in Nature Geosciences concluded heretically that ‘it is at present impossible to accurately determine climate sensitivity to carbon dioxide’ (high sensitivity underpins the entire IPCC argument), yet presaged this with the absurd remark: ‘Earth’s climate can only be stabilised by bringing carbon dioxide emissions under control in the 21stcentury.'”

In fact, the paper that was published in Nature Geoscience (PDF), a relatively short ‘Commentary’, was far from heretical – it argued that it is important to understand the contribution to anthropogenic warming from methane, ozone and black carbon, as well as carbon dioxide.

And the claim that “high sensitivity underpins the entire IPCC argument” is simply not true. The IPCC Fourth Assessment Report estimates, from the published literature, that the likely (i.e. more than 66 per cent chance) value of climate sensitivity (defined as the global average surface warming following a doubling of atmospheric concentrations of carbon dioxide) lies between 2°C and 4.5°C, with a best estimate of 3°C. As the report points out, values of high sensitivity, much larger than 4.5°C, cannot be ruled out. However extremely low values of climate sensitivity of less than 1.5ºC, which are promoted by ‘sceptics’, are very unlikely (i.e. less than 10 per cent chance) and are increasingly at odds with the available evidence. Atmospheric concentrations of carbon dioxide are currently about 40 per cent higher than levels before industrialisation and global average temperature has risen by about 0.8ºC.

Overall, the article by Ridley and Lewis is a biased account of a dispute about the best way of dealing with inadequate data about temperature trends in Antarctica, framed within an exaggerated rhetoric about the alleged bias of the review and publication process for journal papers on climate change.

The article is rather typical of the one-sided contributions on climate change that are offered by The Spectator – at the end of the article by Ridley and Lewis is an instruction to readers to turn to an advert for an event, to be hosted by the magazine on 29 March 2011, at which the following motion will be debated: “The global warming hysteria is over. Time for a return to sanity”.