climate consensus and contrarians

8/3/2019 Climate Consensus and Contrarians

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DRAFT

Climate, Consensus, and Contrarians 1

Jay Odenbaugh Department of Philosophy Environmental Studies Lewis and Clark College [email protected]

I. Introduction. In debates over global climate change, much is made over the consensus

concerning the effects of human-induced greenhouse gas emissions on the Earths temperature.

Contrarians correctly note that science is partially structured around dissent and criticism. Thus,

they charge scientific consensus is irrelevant and even harmful to scientific inquiry. In this essay,

I first present the contrarians argument. Second, I argue this criticism is irrelevant because

claims about the scientific consensus concern how policymakers form their beliefs and not

scientists themselves. Third, I argue that policymakers should form their beliefs about global

climate change based on the scientific consensus when that consensus is reliable indicator of truth and explore when this is so by considering Condorcet Jury Theorems and the structure of

Intergovernmental Panel on Climate Change.

II. Scientific Consensus. Many contrarians, and others of course, correctly note that agreement

amongst scientists doesnt make the agreed upon proposition true nor even guarantees that it is

true.2 Historian Naomi Oreskes writes,

1 I wish to thank all those who attended my talk at the twelfth Inland Northwest Philosophy Conference andprovided fruitful feedback and questions; specifically Stephen Crowley, Steve Gardiner, Bruce Glymour, Ben Hale,Kristen Intemann, Kristin Shrader-Frechette, Michael ORourke, Matt Slater, Mariam Thalos, Allen Thompson,Michael Trestman, and Dennis Walsh.

2 Naomi Or eskes writes, If the history of science teaches anything, its humility. There are numerous historicalexamples where expert opini on turned out to be wrong Moreover, in any scientific community, there are always
mailto:[email protected]:[email protected]:[email protected]


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If the history of science teaches anything, its humility. There are numerous historicalexamples where expert opinion turned out to be wrong Moreover, in any scientificcommunity, there are always some individuals who depart from generally acceptedviews, and occasionally they turn out to be right. At present, there is a scientific

consensus on global warming, but how do we know its not wrong? (2007, 65)

We can summarize this claim as follows:

(C ) Scientific consensus about a proposition does not make or guarantee that it is true.

Why accept ( C )? Because, as Oreskes notes, in the history of science there are propositions

which had near unanimous acceptance but which were latter shown to be false. For example,

scientists believed that the Earth was at the center of our solar system, continents do not drift,

and that species are not related by common descent. Examples such as these suffice to show that

propositions are not made true by unanimous consent. 3 Thus, many contrarians believe interest in

scientific consensus reflects political concerns as opposed to epistemological ones. Novelist

Michael Crichton writes,

Lets be clear: the work of science has nothing whatever to do with consensus. Consensusis the business of politics. Science, on the contrary, requires only one investigator who

happens to be right, which means that he or she has results that are verifiable by referenceto the real world. In science consensus is irrelevant. What is relevant is reproducibleresults. The greatest scientists in history are great precisely because they broke with theconsensus. There is no such thing as consensus science. If i ts consensus, it isn t science.If its science, it isn t consensus. Period. (http://www.crichton-official.com/speech-alienscauseglobalwarming.html )4

Similarly, MIT professor of meteorology and contrarian Richard Lindzen writes,

some individuals who depart from generally accepted views, and occasionally they turn out to be right. At present,there is a scientific consensus on global warming, but how do we know its not wrong? (2007, 65) 3 A technical aside: there are propositions which can be made true by universal assent; namely those whose truthconditions concern universal assent. However, those very propositions are not made true by universal assent to them .Also, on one type of pragmatist theory of truth, a proposition is true just in case it would be agreed with by fullyinformed and fully rational inquirers who had an indefinite amount of time to investigate them.

4 For a popular argument for these sorts of claims, see Horner (2007) especially his chapter five and fiction writerMichael Crichtons critique of climate change science in his novel State of Fear .
http://www.crichton-official.com/speech-alienscauseglobalwarming.htmlhttp://www.crichton-official.com/speech-alienscauseglobalwarming.htmlhttp://www.crichton-official.com/speech-alienscauseglobalwarming.htmlhttp://www.crichton-official.com/speech-alienscauseglobalwarming.htmlhttp://www.crichton-official.com/speech-alienscauseglobalwarming.htmlhttp://www.crichton-official.com/speech-alienscauseglobalwarming.html


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With respect to science, the assumption behind consensus is that science is a source of authority and that authority increases with the number of scientists. Of course, science isnot primarily a source of authority. Rather, it is a particularly effective approach toinquiry and analysis. Skepticism is essential to science; consensus is foreign. (Horner

2007, 86)

Both Crichton and Lindzen make the same mistake of course just because scientists agree that

a proposition is true doesnt make it true. However, this obvious point is consistent with the fact

that most scientists believe a proposition is true can be good evidence for others to believe that

proposition. In Lindzens terms, if science is an effective approach to inquiry and analysis this

may give us good reason to treat scientists agreement as aut horitative. Lastly, contrarian writer

Chris Horner writes,

There is no scientific consensus that extreme or damaging global warming will occur or that Man is the principal or even a quantifiable determinant of climate, let alone thatglobal warming would be a bad thing (past warmings yes, including warmer than thepresent have always been positive; dark ages have tended to coincide with coolingphases). In fact, it is difficult to identify another issue of scientific inquiry over which thedebate rages more intensely. (2007, 82)

Horner provides us with a bait -and- switch; ignore the consensus surrounding the proposition

under discussion and suggest there is no consensus regarding a different one. As we shall see,

there is a consensus regarding human s having a discernable effect on the Earths climate

independent of whether these effects will be catastrophic. 5

To be very clear, both dissent and consensus matter to scientific practice. 6 First, it is in

the interest of any research group that their hypotheses be confirmed and it is in the interest of

their opposition that those hypotheses be disconfirmed. Given this dynamic, critical engagement

5 It is also helpful to note that there is also a consensus regarding climate change economics as well. First, the costsof inaction are greater than action and that the costs of dealing with anthropogenic climate change will be a tinyfraction of GDP.

6 I am indebted to an anonymous reviewer for noting this point.


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occurs and dissent is a crucial element in weeding out reliable from unreliable work, truths from

falsehoods (Hull 1988, Kitcher 1993). Second, science, and its progress, requires consensus.

Research programs require a large degree of agreement amongst scientists regarding aims,

methods, and theories. Without such agreement, research could not take place since there would

not be common questions, strategies, representations of the phenomena, and tools to evaluate

those representations. Likewise, rational transitions between programs necessitates there are

agreed upon elements which can used to make rational decisions regarding the disputed elements

and recent work concerning the history of science demonstrates such piecemeal transitions

(Laudan 1986). When theories are in dispute one must use agreed upon methods to pick the

better theory, when there is a disagreement regarding proper methodology one must use aims to

determine the best means, and so on.

Contrarians should not deny the proper importance of agreement and dissent in science.

In the next section, I want to document the consensus that exists regarding anthropogenic climate

change and thereafter I will carefully articulate why this consensus matters.

III. Global Climate Change Consensus. To zero in on the debate, let s use the following claim:

(GW ) Average surface temperatures are increasing in part because of human greenhousegas emissions.

Naomi Oreskes (2004) forcefully argues there is close to complete agreement amongst

professional climate scientists regarding ( GW )s truth. She and her graduate students surveyed

over 928 abstracts of articles published in peer-reviewed journals with the search term global

climate change through the Institute of Scientific Informations Web of Science. Each essay

was placed in one of six categories: (1) those explicitly endorsing the consensus position, (2)

those explicitly refuting the consensus position, (3) those discussing methods and techniques for


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measuring, monitoring, or predicting climate change, (4) those discussing potential or

documenting actual impacts of climate change, (5) those dealing with paleoclimatic change, and

(6) those proposing mitigation strategies. Ultimately what they found was there were no papers

of category (2).

Figure 1 A Web of Science analysis of 928 abstracts using the keywords global climate change. Nopapers in the sample provided scientific data to refute the consensus position on global climate change(Oreskes 2004).

That is, s he found no essay which disagreed with the claim Global climate change is occurring,

and human activities are at least part of the reason why .

There are variety of criticisms leveled at Oreskes study. One criticism raised by Roger

Pielke Jr. (2005) is that the Oreskes study does not represent the variance consistent with those

who agree with the IPCCs reports. That is, one can agree with ( GW ) but disagree over many

other propositions concerning global climate change. This is perfectly correct but irrelevant to

the studys methods and findings which concern the focal proposition ( GW ). Others have

suggested some duplicity on Oreskes part given that in the 2004 paper she claimed they searched

with the terms climate change which would have turned up ten thousand papers but this a

simple mistake which was later corrected in Science . Most importantly, one might argue that

consiste ncy with the proposition Global climate change is occurring, and human activities are at


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least part of the reason why is insufficient to demonstrate agreement with the proposition.

Oreskes provides the correct response to this point.

If a conclusion is widely accepted, then it is not necessary to reiterate it within thecontext of expert discussion. Scientists generally focus their discussions on questions thatare still disputed or unanswered rather than on matters about which everyone agrees.(2007, 72) 7

Similarly, one would not see common descent argued for or explicitly affirmed in an essay in

Evolution or American Naturalist ; it is taken for granted. Hence, if one only included support by

those papers which provide explicit acceptance, then it would underestimate the acceptance of

evolution and by analogy global climate change as in part human-caused.

Lest one think this study is a fluke or non-representative, consider the following recent

study done by Doran and Zimmerman (2009). They sent a survey to 10, 257 earth scientists. The

individuals surveyed came from a database (Keane and Martinez (2007)) of geosciences faculty,

researchers at state geological facilities associated with local universities, researchers at U.S.

research facilities (U.S. Geological Survey, NASA, and NOAA) and the U.S. Department of

Energy national laboratories (2009, 21). Of the questions asked, their essay discusses two:

1. When compared with pre-1800s levels, do think that mean global temperatures havegenerally risen, fallen, or remained relatively constant?

2. Do you think human activity is a significant contributing factor in changing mean globaltemperatures?

Here are their results for question (2).

7 Michael Crichton writes, Finally, I would remind you to notice where the claim of consensus is invoked.Consensus is invoked only in situations where the science is not solid enough. Nobody says the consensus of scientists agrees that E = mc2. Nobody says the consensus is that the sun is 93 million miles away. It would neveroccur to anyone to speak that way (http://www.crichton-official.com/speech-alienscauseglobalwarming.html ). Thisis false. The empirical evidence regarding evolution by common descent is solid and yet evolutionary biologists dorefer to the consensus regarding it in response to creationists and IDers.
http://www.crichton-official.com/speech-alienscauseglobalwarming.htmlhttp://www.crichton-official.com/speech-alienscauseglobalwarming.htmlhttp://www.crichton-official.com/speech-alienscauseglobalwarming.htmlhttp://www.crichton-official.com/speech-alienscauseglobalwarming.html


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Figure 2 Response distribution to survey question (2) and the general survey data come from a 2008Gallop poll (Doran and Zimmerman 2009).

Their results showed that 90% answered risen to (1) and 82% answer yes to (2). Of those

who listed climate science as their area of expertise and who publish ed more than 50% of their

recent peer reviewed papers in this area, 96.2% (76/79) answered risen to (1) and 97.4%

(75/77) to (2). 8

One response to such work is So what? We know that there are dissenters with regard

to (GW ). Why does their opinion not receive differential weighting? One common argument

given for dismissing contrarians views has been offered in Ross Gelbspans book The Heat is

On (1997). Gelbspan documents how contrarian scientists have been funded by the oil and gas

industry and many in this industry have generally been skeptical of ( GW ).9 The conclusion he

reaches is that these contrarians deny ( GW ) for financial gain and as such they should be ignored.

8 It is interesting to note that amongst meteorologists, those that answered yes to (2) are 64% (23/36).

Meterologists however study very different scales than climatologists; we generally do ask not cellular biologistswhether the theory of evolution is true.

9 Recently, due to the work of Joseph Romm, the term contrarian has been sometimes replaced with the termsdenier and delayer with regard to global climate change. A denier deni es the truth or justification for ( GW ). Adelayer accepts ( GW ) but claims that we are impotent to do anything about it, it would be too expensive, or there aremore ethical and/or efficient ways of using our GNPs. Examples of these two positions would be Patrick Michaelsand Bjorn Lomborg. A contrarian is typically a denier but some are delayers.


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Lets consider one example. Patrick Michaels was a professor of Environmental Science at the

University of Virginia. He is affiliated with the George C. Marshall Institute and the Cato

Institute both of which are conservative think tanks. Gelbspan and others claim that he has

received more than $115,000 from coal and energy interests. A quarterly publication World

Climate Review which Michaels founded was funded by the contrarian group Western Fuels.

Finally, he was paid $100,000 by the electric utility Intermountain Rural Electric Association

which also is contrarian in nature. This is a suggestive argument; however, it is a circumstantial

ad hominem. That is, we are conflating the truth of the denial of ( GW ) and Michaels

associations. To correct the Gelbspan argument we would need to show that Michaels denies

(GW ) because of the money he has received which requires more evidence than Gelbspan has

supplied. 10

Having said this, one can argue indirectly that contrarians denial of ( GW ) is indicative of

bias. If someone trained in climate science offers arguments whose premises are poorly

supported and contrary evidence is commonplace amongst said scientists, then this is evidence

that they are distorting the facts. For example, it is common for contrarians to argue that since we

cannot successfully predict weather more than twelve days hen ce, we shouldnt trust the

projections of global circulation models. Likewise, many offer alternative explanations of the

recent warming such as a solar variability hypothesis. However, in both cases, there are ready

responses to these claims with which climate scientists are familiar. For example, some

contrarians find locales where temperature data show a decrease in temperatures rather than an

increase; however, such isolated data sets are not terribly relevant to the claim that humans are

causing an increase in average surface temperatures. Likewise, though the sun has been more

10 I thank Kristin Shrader-Frechette for thoughtful comments on this point. Naomi Oreskes and Erik Conway (2008)attempt to fill in such an argument exploring strategies of the George C. Marshall Institute.


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active in the last sixty years than in the last 1150 years, the correlation between solar activity

and temperature has disappeared since the 1970s (Usoskin et. al. (2005), Lockwood et. al.

(2007)). Hence, an increase in average surface temperature cannot be accounted for by changes

in solar activity.

IV. Why (and When) Consensus Matters. As I noted above, agreement and dissent are

absolutely essential to science. However, contrarians fail to clearly distinguish between two

different epistemic communities climate scientists and policymakers. Climate scientists attempt

to determine the truth value of ( GW ) in light of the empirical evidence. However, whenpolicymakers are making decisions in which the truth value of ( GW ) is relevant, things are

importantly different. Why? Because policymakers do not have the relevant expertise in the

matters of interest. 11 Suppose you are not a climate scientist but are a policymaker; should you

believe ( GW )? Well, if the majority of climate scientists do believe it and you are in no position

to seriously evaluate the evidence on your own, then it seems that you should. Your evidence

will not directly involve tree rings, glacial retreat, ice cores, boreholes, satellite measurements,

computer simulations, etc. since you dont understand these topics. Rather, you must determine

who is a reasonable authority on the issue and form your beliefs in accordance with their

11 Richard Lindzen writes, [N]onscientists generally do not want to bother with understanding the science.Claims of consensus relieve policy types, environmental advocates and politicians of any need to do so. Such claimsalso serve to intimidate the public and even scientists especially those outside the area of climate dynamics. (http://www.opinionjournal.com/extra/?id=110008597) . I am in no position to say whether non-scientists want tounderstand science or not and consensus claims neednt relieve policymakers from having any need to do so.However, Lindzen does not take seriously the competing claims on policymakers time. Regardless of policymakersscientific aptitudes, how is one to become well-versed in climate change physics, environmental economics, andgreen technology along with healthcare policy, international terrorism, and so on?
http://www.opinionjournal.com/extra/?id=110008597)http://www.opinionjournal.com/extra/?id=110008597)http://www.opinionjournal.com/extra/?id=110008597)http://www.opinionjournal.com/extra/?id=110008597)


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opinion. 12 Still, as with ( C ) above, consensus doesnt guarantee a proposition is true, so when is a

consensus regarding some proposition like ( GW ) a reliable indicator of its truth?

In order to explore the issue, consider the following simple model. Suppose the

probability that every expert i is correct about a proposition P being true or false is r i, for all i, 1

> r i > , and the correctness of a expert js opinion is probabilistically independent of every

other expert i. It can be shown that if the majority of n experts believe that P is correct, then the

probability of their opinion being correct is greater than r i and that as n increases the probability

that they are correct gets larger and larger and in the limit is one. This is an instance of

Condorcets jury theorem. 13 But there are two problems with applying this model to the climate

change case. First, we assume that each expert has the same greater than chance of correctly

determining a propositions truth value and this is unlikely. Second, it is unreasonable to assume

that each expert s judgment is independent of every other statistically speaking. For example,

scientists encounter and evaluate much of the same information, utilize similar methods, have

shared aims, and may even mimic the opinions of others. In an unpublished manuscript, James

Hawthorne has generalized Condorcets Jury Theorem in which these assumptions are relaxed

(see Ladha (1992) and Estlund (1994) as well). Lets consider Hawthornes work first a nd then

his response to each of these worries.

Hawthornes Condorc et Jury Theorem depends on four factors: number of experts n, the

average competence level r , the variance of r , s2, and the covariance of individual competence

12 I should note that this point is not unique to the environmental sciences, far from it. For example, the epistemic justification for many of our beliefs depends on the reliability of authorities (Goldman 1999). For example, most of us could not prove the fundamental theorem of calculus which shows how the differentiation and integration arerelated. However, in our mathematical work, we presuppose that it is true and can be shown so.

13 Strictly speaking, we must assume n > 2 and is odd. However, the latter simplification can be easily relaxed. Ithank Bruce Glymour and an anonymous reviewer for providing useful discussion on Condorcets Jury Theorem andways of relaxing its assumptions.


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levels. 14 As before, let us consider two mutually exclusive and exhaustive propositions P and Q

(though we could generalize even here). The competence level of an expert i with regard to Ps

truth is the probability r i that they accept P when P is true Pr[( p i = 1)/ P ] = r i. Similarly, Pr[( q i

= 1)/ Q] when i accepts Q . Let n be the total number of experts and so the average competence

level isn

i inr r

1 / . The variance s2 in r is determined in the usual way. The covariance

measures the association of expert i and js votes, or r ji . Formally, ] / )1&1Pr[( P p pr i j ji .

If j and i vote independently, then r ji = r jr i since )1Pr()1Pr(] / )1&1Pr[( i ji j p pP p p .

On the other hand, if r ji r jr i, then )1Pr()1Pr(] / )1&1Pr[( i ji j p pP p p . Thus,

i j ji r r r measures the degree to which i and j tend to vote in agreement. If 0i j ji r r r , then i has

no influence on j and cov = 0; otherwise, i may have positive or negative influence on j. Finally,

as it turns out, n, r , s2, and cov are related by the following equation (where 2 is the variance of

expected value of r ),

cov] / )1[() / (] / )1([ 22 nnnsnr r

Let % p =n

ni in p / be the fraction of votes for P . When % p > then the majority have voted in

favor of P and if % p < , then the majority have voted for Q. By inspecting the equation above,

Pr[(% p > )/ P ) 1 when n is large, r is greater than , and cov is small; that is, the majority

will probably correctly accept P .

Hawthornes g eneralized Condorcet Jury Theorem discharges the above idealizations.

First, the theorem depends on the average competence level r and does not require that each r i >

14 Here I use slightly different notation than Hawthorne for exegetical purposes. It is also worth noting he provesseveral different Condorcet Jury Theorems including one where the distribution of the votes for a proposition k/n where k is the number of votes for the proposition and n is the number voters is normally distributed.


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or are the same and their variance is expressed by s2. Second, his theorem holds even when

cov 0; that is, when experts i and js opinions are dependent provided n or r is relatively large.

One important issue to note is that is that probabilistic dependence between voters occurs when

the fact that i believes or votes P affects js believing or voting P . The fact that i and j

encounter and evaluate the same information, use similar methods, or have common aims does

not imply probabilistic dependence.

To be clear, I havent argued that the assumptions of the Condorcet model are true of the

community of climate scientists. I have attempted to demonstrate that the idealizations that

appear to challenge the models applicability can be relaxed and that if the models assumptions

were true, then it would be explain why the consensus would be evidence of the truth of ( GW ).

That is, I have provided a how possibly explanation . If the assumptions of Hawthornes

Condorcet Jury Theorem were met (and it is not unreasonable to suppose they are), then this

would bring about a majority who are likely to be correct. To argue that the Condorcet model

provides a how-actually explanation would require a lot more empirical evidence than I have

offered. Nevertheless, we see that a majority not even a consensus is likely to be correct

about a propositions truth when they are numerous, exhibit better than chance average

competence level, and opinions are relatively independent. Not every consensus is truth

indicative but some are.

If the consensus regarding climate change is truth indicative, then policy-makers should

apportion their degrees of belief in ( GW ) with respect to this consensus. The Intergovernmental

Panel on Climate Change (IPCC) is just such an organization that represents this consensus. The

IPCC is one of the largest science-related projects ever created. It does not conduct research of

its own; rather, it evaluates the work of scientists around the world and then synthesizes this


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As we can see, each IPCC assessment involving enormous numbers of scientists. The

IPCC Fourth Assessment Report (AR4) included more than 2500 scientific expert reviewers,

more than 800 contributing authors, and more than 450 lead authors.

Of these, the Working

Group 1 report (including the summary for policy makers) included contributions by 600 authors

from 40 countries, and over 620 expert reviewers, a large number of government reviewers, and

representatives from 113 governments. It should also be noted that the IPCC is not the only

organization who have stated that humans are having an effect on our climate through

greenhouse gas emissions. The American Academy of Science, the American Meteorological

Association, the American Geophysical Union, and the American Association for the

Advancement of Science have issued similar statements. 16

So, here is one way consensus matters consensus matters amongst experts when it is the

reliable indicator of the truth of a proposition which is relevant to the decisions of policymakers.

A consensus is reliable indicator of truth when it occurs amongst a majority which is sufficiently

large, where the average competence level is greater than chance, and where the experts

generally vote their understanding of the best evidence. Scientific consensus, contrary to

contrarians, does not threaten the process of science. Dissent is crucial for as we say normal

science. Contrarians should continue their cr iticism and battle it out in peer reviewed journals

(which they generally do not do). However, when it comes to non-expert opinion and specifically

environmental policy, consensus matters a lot. This point simply pivots on drawing a distinction

16 Stephen Gardiner has argued in conversation that the opinions of the IPCC are often more conservative than basicclimate science would suggest. This is due in large part to the very nature of how agreement amongst actors isproduced. If this is correct, then the IPCC will often understate the seriousness of global climate change impacts. Onthis point, Timothy Flannery writes, Yet in spite of the IPCCs faults, its assessment reports, which are issued everyfive years, carry weight with the media and government precisely because they represent a consensus view. If theIPCC says something, you had better believe it and then allow for the likelihood that things are far worse than itsays they are ( 2006, 246).


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between the epistemic community of scientists and that of policymakers. When Michael

Crichton writes, When did skeptic become a dirty word in science? When did a skeptic require

quotation marks around it? he clearly is confusing the two.17

V. Conclusion. In this essay, I have presented the contrarians argument against consensus

science . Second, I argued that we should distinguish between those beliefs or degrees of belief

of scientists themselves or policy-makers. Third, I argued that policy-makers should form their

beliefs or degrees of belief in accordance with climate scientists themselves reflecting the

consensus position that is well-documented.

Bibliography

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