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False Consensus: The 97 Percent Canard (Oreskes study debunked)

By Robert Bradley Jr. -- October 10, 2017

“It is now widely agreed Oreskes did not distinguish between articles that acknowledged or assumed some human impact on climate, however small, and articles that supported IPCC’s more specific claim that human emissions are responsible for more than 50 percent of the global warming observed during the past 50 years.”

“Her definition of consensus also is silent on whether man-made climate change is dangerous or benign, a rather important point in the debate.”

” Oreskes’ literature review inexplicably overlooked hundreds of articles by prominent global warming skeptics…. More than 1,350 such articles (including articles published after Oreskes’ study was completed) are now identified in an online bibliography.”

The second edition of Why Scientists Disagree About Global Warming: The NIPCC Report on Scientific Consensus. (Heartland Institute: 2015), edited by Craig Idso, (the late) Robert Carter, and S. Fred Singer, took pains to refute the  study whose “97 percent consensus” claim has become a ‘sound bite’ for climate alarmists.

As long as the Oreskes study is cited, some ready rebuttal points  should be kept in mind. The following passages are from the “Flawed Surveys” section (pp. 10-13) of 2015 edition of Why Scientists Disagree About Global Warming, which can be read online here (full citations are provided at this link).

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Claims of a “scientific consensus” on the causes and consequences of climate change rely on a handful of essays and reports that either survey scientists or count the number of articles published in peer-reviewed journals that appear to endorse the positions of IPCC.  As this section reveals, these surveys and abstract-counting exercises are deeply flawed and do not prove what those who cite them claim. 

Oreskes, 2004

The most frequently cited source for a “consensus of scientists” is a 2004 essay for the journal Science written by science historian Naomi Oreskes (Oreskes, 2004).

Oreskes reported examining abstracts from 928 papers reported by the Institute for Scientific Information database published in scientific journals from 1993 and 2003, using the keywords “global climate change.” Although not a scientist [sic], she concluded 75 percent of the abstracts either implicitly or explicitly supported IPCC’s view that human activities were responsible for most of the observed warming over the previous 50 years while none directly dissented.

Oreskes’ essay, which was not peer-reviewed, became the basis of a book, Merchants of Doubt (Oreskes and Conway, 2010), and an academic career built on claiming that global warming “deniers” are a tiny minority within the scientific community, and even a movie based on her book released in 2015. Her 2004 claims were repeated in former Vice President Al Gore’s movie, An Inconvenient Truth, and in his book with the same title (Gore, 2006).

It is now widely agreed Oreskes did not distinguish between articles that acknowledged or assumed some human impact on climate, however small, and articles that supported IPCC’s more specific claim that human emissions are responsible for more than 50 percent of the global warming observed during the past 50 years. The abstracts often are silent on the matter, and Oreskes apparently made no effort to go beyond those abstracts. Her definition of consensus also is silent on whether man-made climate change is dangerous or benign, a rather important point in the debate.

Oreskes’ literature review inexplicably overlooked hundreds of articles by prominent global warming skeptics including John Christy, Sherwood Idso, Richard Lindzen, and Patrick Michaels. More than 1,350 such articles (including articles published after Oreskes’ study was completed) are now identified in an online bibliography (Popular Technology.net, 2014).

Oreskes’ methodology was flawed by assuming a nonscientist [sic] could determine the findings of scientific research by quickly reading abstracts of published papers. Indeed, even trained climate scientists are unable to do so because abstracts routinely do not accurately reflect their articles’ findings.

According to In-Uck Park et al. in research published in Nature (Park et al., 2014), abstracts routinely overstate or exaggerate research findings and contain claims that are irrelevant to the underlying research. The authors found “a mismatch between the claims made in the abstracts, and the strength of evidence for those claims based on a neutral analysis of the data, consistent with the occurrence of herding.” They note abstracts often are loaded with “keywords” to ensure they are picked up by search engines and thus cited by other researchers.

Oreskes’ methodology is further flawed, as are all the other surveys and abstract-counting exercises discussed in this chapter, by surveying the opinions and writings of scientists and often nonscientists who may write about climate but are by no means  experts on or even casually familiar with the science dealing with attribution – that is, attributing a specific climate effect (such as a temperature increase) to a specific cause (such as rising CO2).

Most articles simply reference or assume to be true the claims of IPCC and then go on to address a different topic, such as the effect of ambient temperature on the life-cycle of frogs, say, or correlations between temperature and outbreaks of influenza. Attribution is the issue the surveys ask about, but they ask people who have never studied the issue. The number of scientists actually knowledgeable about this aspect of the debate may be fewer than 100 in the world. Several are prominent skeptics (John Christy, Richard Lindzen, Patrick Michaels, and Roy Spencer, to name only four) and many others may be.

Monckton (2007) finds numerous other errors in Oreskes’ essay including her use of the search term “global climate change” instead of “climate change,” which resulted in her finding fewer than one-thirteenth of the estimated corpus of scientific papers on climate change over the stated period. Monckton also points out Oreskes never stated how many of the 928 abstracts she reviewed actually endorsed her limited definition of “consensus.”

Medical researcher Klaus-Martin Schulte used the same database and search terms as Oreskes to examine papers published from 2004 to February 2007 and found fewer than half endorsed the “consensus” and only 7 percent did so explicitly (Schulte, 2008). His study is described in more detail below.

References

Gore, A. 2006. An Inconvenient Truth: The Planetary Emergency of Global Warming and What We Can Do About It. Emmaus, PA: Rodale Press.

Monckton, C. 2007. Consensus? What consensus? Among climate scientists, the debate is not over. Washington, DC: Science and Public Policy Institute.

NASA, 2015. Scientific consensus: Earth’s climate is warming. National Aeronautics and Space Administration. Website. http://climate.nasa.gov/scientific-consensus/. Last viewed on October 30, 2015.

Oreskes, N. and Conway, E.M. 2010. Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues From Tobacco Smoke to Global Warming. New York: NY: Bloomsbury Press.

Park, I.-U., Peacey, M.W., and Munafo, M.R. 2014. Modelling the effects of subjective and objective decision making in scientific peer review. Nature 506 (7486 February): 93–96.

Popular Technology.net. 2014. 1350+ peer-reviewed papers supporting skeptic arguments against ACC/AGW alarmism. Website (February 12). http://www.populartechnology.net/2009/10/peer-reviewed-papers-supporting.html. Last viewed on September 23, 2015.

Schulte, K-M. 2008. Scientific consensus on climate change? Energy & Environment 19 (2 March): 281–286. doi: 10.1260/095830508783900744.

3 Comments


  1. Jon Boone  

    Thanks for the reminder about these issues, Rob, and for the plug for the Second Edition of the NIPCC publication. No convincing evidence exists to support the view that the earth is globally warming. After discounting the dubious urban heat island effect numbers game and accounting properly for margin of error on temperature measurement, the “average earth temperature seems to be what it was a hundred years ago, two hundred years ago–back when measurement was relatively imprecise, calling into question the accuracy of baseline temperatures.

    There is evidence of increased CO2 in the atmosphere, which likely accounts for increased vegetation in a number of climes. But how much of this increase is actually due to the influence of culture is uncertain. The CO2 increase is fractional and adds what may only be a trivial amount to the already minute levels sprinkled into the atmosphere for eons of time. There is no hard evidence it is non-trivial. I should add that the EARTH IS NOT A GREENHOUSE.

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  2. Paul Dellevigne  

    One further note. I led the team the developed the first digitally published version of the Science Citation Index and I am very familiar with its structure. It is important to understand the “Keywords” in that data are created by editors based on a quick read, probably of the abstract. I suspect that few would add the keywords “Climate Change” for papers that actually covered radiative forcing of CO2. It seems certain to bias the sample to the “believers” in the term that was not as widely used in 2004 as today outside the disciples of James Hansen.

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