What Oreskes got wrong

Dr. Benny Peiser, of Liverpool John Moores University in the UK, conducted a search of the peer-reviewed literature on the ISI Web of Science database between 1993 and 2003. He found not 928 but more than 12,000 papers mentioning the phrase “climate change”. When he pointed this out, the editors of Science were compelled to publish an erratum to the effect that the search term which Oreskes had used was not, as stated in her essay, “climate change” but rather “global climate change”. Accordingly, Oreskes’ essay had covered not the entire corpus of scientific papers on climate change over the stated decade but fewer than one-thirteenth of them.

Dr. Peiser used “global climate change” as a search term and found 1,117 documents using this term, of which 929 were articles and only 905 also had abstracts. Therefore it is not clear which were the 928 “abstracts” mentioned by Oreskes, and Science did not, as it would have done with a peer-reviewed scientific paper, list the references to each of the “abstracts”.

Significantly, Oreskes’ essay does not state how many of the 928 papers explicitly endorsed her very limited definition of “consensus”. Dr. Peiser found that only 13 of the 1,117 documents – a mere 1% – explicitly endorse the consensus, even in her limited definition.

Dr. Peiser’s research demonstrated that several of the abstracts confounded Oreskes’ assertion of unanimity by explicitly rejecting or casting doubt upon the notion that human activities are the main drivers of the observed warming over the last 50 years. Thus, in Oreskes’ sample, more than twice as many appeared to have explicitly rejected or doubted the “consensus” as had explicitly endorsed it.

According to Dr. Peiser, fewer than one-third of the papers analyzed by Oreskes either explicitly or implicitly endorsed the “consensus”, contrary to Oreskes’ assertion that the figure was 75%. In addition, 44 abstracts focused on the natural as opposed to anthropogenic causes of climate change, and did not include any direct or indirect link or reference to human actitivies, carbon dioxide or other greenhouse gas emissions, let alone anthropogenic forcing of recent climate change. More than half of the abstracts did not mention anthropogenic climate change at all and could not, therefore, reasonably be held to have commented either way upon the “consensus” as defined by Oreskes.

Dr. Peiser wrote to Science to point out these and other anomalies in Oreskes’ essay. The editors of Science at first asked him to shorten his letter: then, after he had sent in his shortened version, they changed their minds and refused to publish it –

“After realizing that the basic points of your letter have already been widely dispersed over the internet, we have reluctantly decided that we cannot publish your letter. We appreciate your taking the time to revise it.”

In fact, Dr. Peiser had been careful to ensure that none of his material had appeared in any public forum, whether on the Internet or otherwise. In any event, it is reprehensible that a learned journal should publish defective material and should then, in effect, expect its readers to surf the Internet to find the truth.

The editors of Science also refused to publish any of the numerous other letters that they had received pointing out the deficiencies in Oreskes’ analysis.

At the time, the editors of Science had received (and rejected) a research paper giving the results of a survey of some 500 international climate researchers conducted by Professors Dennis Bray and Hans von Storch of the German Institute for Coastal Research. The survey had found that –

“a quarter of respondents still question whether human activity is responsible for the most recent climate changes.”

Dr. Peiser has commented:

“The decision to publish Oreskes' claim of general agreement (just days before an important UN conference on global warming, the Tenth Conference of the Parties to the UN Convention on Climate Change), was apparently made while the editors of Science were sitting on a paper that showed quite clearly the opposite.

“It would appear that the editors of Science knowingly misled the public and the world's media.

“In my view, such unethical behaviour constitutes a grave contravention, if not a corruption of scientific procedure. This form of unacceptable misconduct is much worse than the editors' refusal to publish the numerous letters and rebuttals regarding Oreskes' flawed study.”

Furthermore, what of the countless research papers that show global temperatures were similar or even higher than today’s during the Holocene Climate Optimum and the Medieval Warm Period, when atmospheric CO₂ levels were much lower than at present?

What of the papers showing that solar variability is a key driver of recent climate change, and that in the past 70 years the Sun has been more active, for longer, than at almost any comparable period in the past 11,400 years?

What of the papers echoing Lorenz (1963), who, in the paper that founded chaos theory, stated and demonstrated his famous theorem that the climate is a mathematically-chaotic object that is by its nature unpredictable unless one fully understands not only all the relevant evolutionary processes but also the initial state of the global climate to a precision that is in practice altogether unattainable?

There are hundreds of learned papers, many of them written by the world's leading experts in climatology and related fields, that have raised serious reservations about the notion of a “consensus” as to the alarmist presentation of climate change. Many of these papers explicitly reject the “consensus”, even in the limited sense used by Oreskes.

There is no such thing as a “scientific consensus”, except in a very limited sense. This may be readily demonstrated by quotation from dozens of papers casting doubt on the “consensus”.

Some examples of papers which fell within Oreskes’ search criteron and within her  chosen timeframe but which she regarded as supportive of her imagined “unanimous” consensus:

Ø      AMMANN et al. (2003) detected evidence for close ties between solar variations and surface climate.

Ø       REID (1997) found that “the importance of solar variability as a factor in climate change over the last few decades may have been underestimated in recent studies”.

Ø       KONDRATYEV and Varotsos (1996) criticize “the undoubtedly overemphasized contribution of the greenhouse effect to the global climate change”.

Two abstracts reviewed by Oreskes directly and bluntly rejected the “consensus” as she had defined it, but she counted them as “consensual” nevertheless:

GERHARD and Hanson (2000):

“The American Association of Petroleum Geologists’ Ad Hoc Committee on Global Climate Issues has studied the supposition of human-induced climate change since the committee’s inception in January 1998. This paper details the progress and findings of the committee through June 1999, At that time there had been essentially no geologic input into the global climate change debate. The following statements reflect the current state of climate knowledge from the geologic perspective as interpreted by the majority of the committee membership. The committee recognizes that new data could change its conclusions. The earth’s climate is constantly changing owing to natural variability in earth processes. Natural climate variability over recent geological time is greater than reasonable estimates of potential human-induced greenhouse gas changes. Because no tool is available to test the supposition of human-induced climate change and the range of natural variability is so great, there is no discernible human influence on global climate at this time.”

FERNAU et al. (1993):

“This article examines the status of the scientific uncertainties in predicting and verifying global climate change that hinder aggressive policy making. More and better measurements and statistical techniques are needed to detect and confirm the existence of greenhouse-gas-induced climate change, which currently cannot be distinguished from natural climate variability in the historical record. Uncertainties about the amount and rate of change of greenhouse gas emissions also make prediction of the magnitude and timing of climate change difficult. Because of inadequacies in the knowledge and depiction of physical processes and limited computer technology, predictions from existing computer models vary widely, particularly on a regional basis, and are not accurate enough yet for use in policy decisions. The extent of all these uncertainties is such that moving beyond no-regrets measures such as conservation will take political courage and may be delayed until scientific uncertainties are reduced.”

Though Oreskes has challenged Dr. Peiser’s analysis by pointing out that the paper by Gerhard and Hansen was not peer-reviewed, her essay appears not to have been peer-reviewed either. It may even be the case that the authors of most or even all of the cited abstracts personally believe that humankind is responsible for more than half of the 0.4C observed warming of the past half century. Dr. Peiser accepts, as does the author of the present paper, that most climate scientists published in the journals probably believe that humankind has contributed more than 0.2C of the 0.4C observed warming over the past half century. But the published papers we have quoted, nevertheless, raise sufficient doubts about important aspects of the imagined “consensus” to demonstrate the falsity of Oreskes’ claim that not one of the abstracts was counter-consensual.

Nor is the explicit and implicit rejection of the "consensus" confined to individual research papers such as those mentioned above. Distinguished scientific organizations such as the Russian Academy of Science and the U.S. Association of State Climatologists have also stated that they are skeptical of the imagined “consensus”.

Dr. Peiser concludes:

“The stifling of dissent and the curtailing of scientific skepticism is bringing climate research into disrepute. Science is supposed to work by critical evaluation, open-mindedness and self-correction. There is a fear among climate alarmists that the very existence of scientific skepticism and doubts about their gloomy predictions will be used by politicians to delay action. But if political considerations dictate what gets published, it's all over for science.”

After examining the erroneous essay by Oreskes, the unsatisfactory circumstances in which it was published, and the failure of Science to correct more than one of its numerous deficiencies, we may conclude as follows:

·          That Oreskes’ essay provides no sound basis for the assertion that a unanimous scientific “consensus” exists on climate change, for, though most climate scientists probably believe that humankind has caused 0.2C of the past half-century’s 0.4C warming, there is no unanimity;

·         That even in the limited sense defined by Oreskes, there were more scientific papers explicitly doubting or even rejecting the “consensus” than explicitly supporting it;

·         That less than half of the papers which Oreskes said had implicitly endorsed the “consensus” had in fact done so;

·           That more than half of the papers which Oreskes considered had not mentioned anthropogenic climate change at all;

·              That the definition of “consensus” in Oreskes’ essay is so limited, and her findings as published so greatly at variance with the content of the papers she reviewed, that the essay provides no justification for her frankly-political contention that –

“our grandchildren will surely blame us they find that we understood the reality of anthropogenic climate change and failed to do anything about it”; and

·         That Science, having been given evidence of Oreskes’ errors before publication, in the form of a direct survey of more than 500 climate scientists, and after it, in the form of several letters pointing out the material errors some of which we have reported here, refused to allow the survey, the letters, or any other correction to appear in print, save only the correction of the database search term which Oreskes had used.

Bringing the analysis of “consensus” up to date

Oreskes’ essay is now outdated. Since it was published, more than 8,000 further papers on climate change have been published in the learned journals. In these papers, there is a discernible and accelerating trend away from unanimity even on her limited definition of “consensus”.

Schulte (2007: submitted) has brought Oreskes’ essay up to date by examining the 539 abstracts found using her search phrase “global climate change” between 2004 (her search had ended in 2003) and mid-February 2007. Even if Oreskes’ commentary in Science were true, the “consensus” has moved very considerably away from the unanimity she says she found.

Dr. Schulte’s results show that about 1.5% of the papers (just 9 out of 539) explicitly endorse the “consensus”, even in the limited sense defined by Oreskes. Though Oreskes found that 75% of the papers she reviewed explicitly or implicitly endorsed the “consensus”, Dr. Schulte’s review of subsequent papers shows that fewer than half now give some degree of endorsement to the “consensus”. The abstract of his paper is worth quoting in full: