The White Queen, by John Tenniel. 1865. Wikimedia Commons/Public Domain. Some rights reserved.“CO2 keeps our planet warm . . . .” — Ian Plimer, Australian climate “skeptic”, Heaven & Earth, p. 411

“Temperature and CO2 are not connected.” — Ian Plimer, Australian climate “skeptic”, Heaven & Earth, p. 278

“Why, sometimes I've believed as many as six impossible things before breakfast.” – The White Queen, in Through the Looking-Glass, and What Alice Found There

Over the last 50 years, climate scientists have built an increasingly clear picture of how the greenhouse gas (GHG) emissions that arise from human economic activity are changing the Earth’s climate. Current atmospheric CO2 levels are higher than at any time since at least a million years ago, and there is no notable scientific dissent from the consensus position that global warming is happening, is human caused, and presents a global problem.

Nonetheless, a small but vocal group of contrarian voices exist—mainly outside the scientific community—who deny that greenhouse gases cause climate change or who dismiss the risk of adverse consequences. This dissent almost never finds expression in the peer-reviewed literature, and when it does, the research typically does not withstand scrutiny.

Instead, the staging ground for climate denial tends to involve internet blogs and other social media. There is strong evidence that the rejection of climate science is primarily driven by ideological factors. Because cutting GHG emissions requires interventions—such as regulation or increased taxation—that interfere with laissez-faire free-market economics, people whose identity and worldview centers around free markets are particularly challenged by the findings from climate science.

When a person’s worldview and identity are threatened by climate change, or other environmental risks, they frequently engage in what is called “identity-protective cognition”. Identity-protective cognition can manifest itself in a variety of ways. Perhaps the most frequent manifestation is that it moderates people’s risk perceptions. However, in the case of climate change, the overwhelming scientific consensus—and the impetus for mitigative policies it entails—poses a particular dilemma for people whose identity is threatened by any potential interference with the free market. A mere moderation of risk perception may be insufficient to justify active rejection of the science and of relevant policy options. What are the cognitive and argumentative options available to them in light of the inconvenient consensus?

The inconvenient consensus

One option is to deny the existence of the consensus. Another option is to accept the consensus (at least tacitly), but to glorify the few contrarian scientists as heroes, often by appealing to Galileo, who oppose the “corrupt” mainstream scientific “establishment.”

A final, conceptually related option is to seek an alternative explanation for the existence of a scientific consensus. Specifically, instead of accepting the consensus as the result of researchers independently converging on the same evidence-based view, it can be explained via the idea of a complex and secretive conspiracy among researchers. Accordingly, many climate contrarian books are suffused with conspiratorial themes, and when asked to indicate their affective responses to climate change, people frequently cite terms such as “hoax”. This finding is unsurprising in light of long-standing knowledge that such thinking is also involved in the rejection of other well-established scientific propositions, such as the link between the HIV virus and AIDS; and denial of the benefits of vaccinations.

However, research to date has mainly focused on the prevalence of such beliefs and their association with attitudes towards science. Here, I broaden the enquiry of conspiracism to embrace an analysis of the (pseudo-) scientific arguments that are advanced against the scientific consensus on climate change, and how they contrast with the positions of the scientific mainstream.

Scientific coherence vs. conspiracist incoherence

A broad stream of opinion among philosophers of science holds that coherence of explanations or theories is a necessary or at least a 'conducive' criterion for truth. Coherence here refers to the criterion that propositions within the theory must not contradict each other—for example, the Earth cannot both be round and flat, and global warming cannot simultaneously be a serious human-caused risk and a natural fluctuation of no concern. Arguably no incoherent theory has ultimately found acceptance by the scientific community.

For the case of climate change, Thagard and Findlay (2011) showed how the mainstream scientific position, namely that GHG emissions from human economic activities are causing the Earth to warm, is coherent and accounts for the available evidence. Their computer simulation of belief revision came to accept the scientific evidence because it maximized coherence among the various pieces of evidence and explanatory propositions.

Standing in opposition to scientific thinking, a known attribute of conspiracist thought is that it can appear incoherent by conventional evidentiary criteria. To illustrate, research has shown that when people reject an official account of an event, they may simultaneously believe in mutually contradictory theories—e.g., that Princess Diana was murdered but also faked her own death. The incoherence does not matter to the person rejecting the official account because it is resolved at a higher level of abstraction, namely the unshakable belief that the official account of an event is wrong. For the case of climate change, Thagard and Findlay (2011) showed that the contrarian position, exemplified by the opinion that global warming is a natural fluctuation, is incoherent in comparison to the mainstream scientific position. Thagard and Findlay were nonetheless able to model why people might accept the incoherent contrarian position by adding emotional components (such as “avoid government intervention”) to the simulation of belief acquisition.

Nonetheless, to date the possibility that climate-contrarian discourse is inherently incoherent has not been systematically examined. I now consider a sample of incoherent positions in detail. In allegiance to Lewis Carroll’s White Queen, who believes six impossible and contradictory things before breakfast, I refer to those states as “Alice through the Looking Glass” states.

'Alice through the Looking Glass' states of denial

Similar to the propositions that Princess Diana was murdered but faked her own death, the quotations of Australian climate 'skeptic' Ian Plimer at the outset of this article are incoherent and cannot both be true. It cannot simultaneously be true that “CO2 keeps our planet warm…” and that “Temperature and CO2 are not connected.” Such incoherence suffuses the public posture of climate denial, suggesting that it cannot lay a strong claim to scientific or intellectual credibility.

Climate sensitivity is low but it is high. One of the most important, but uncertain, variables that determines the extent of future warming is climate sensitivity, defined as the warming that is ultimately expected in response to a doubling of atmospheric CO2 concentrations from preindustrial times. If sensitivity is high, then continued emissions will increase global temperatures more than when it is low. Low estimates of sensitivity (e.g., ≈ 1.5◦C) are therefore favored by contrarians, with the higher range of consensual IPCC estimates being ignored or labeled “alarmist.”

Another popular contrarian argument is that the “climate has changed before”, which entails a commitment to high climate sensitivity: if climate sensitivity were as low as contrarians like to claim (≈ 1.5◦C), then the minute past variation in intensity of the sun, which drove past climate changes in the absence of CO2, could not have caused the observed warming episodes.

Either the climate changed in the past because it is highly sensitive to external forces, in which case we are facing considerable future warming indeed, or its sensitivity to the forces triggered by increasing CO2 concentrations is low, in which case the climate should not have changed in the past. Except that it did.

Global temperature cannot be measured accurately but it stopped warming in 1998. A long-standing contrarian argument has been that the global temperature record is inaccurate and that therefore global warming cannot be measured with any confidence. This argument often cites the fact that thermometers may be located near airports or air conditioner exhausts, thereby distorting and artificially amplifying the temperature trend..

Another long-standing contrarian claim has been that global warming “stopped” in 1998. Although this claim is based on a questionable interpretation of statistical data, it has been a focal point of media debate for the last decade or more.

Either the temperature record is sufficiently accurate to examine its evolution, including the possibility that warming may have “paused”, or the record is so unreliable that no determination about global temperatures can be made.

There is no scientific consensus but contrarians are dissenting heroes. The pervasive scientific consensus on climate change is of considerable psychological and political importance. The public’s perception of the consensus has been identified as a “gateway belief” that is crucial in determining people’s acceptance of policy measures. When people are informed about the broad nature of the consensus, this often alters their attitudes towards climate change. Contrarian efforts to undermine the perception of the consensus have therefore been considerable. For example, the top argument leveled against climate change by syndicated conservative columnists in the US between 2007 and 2010 was the claim that there is no scientific consensus.

A parallel stream of contrarian discourse highlights the heroism of the lone contrarian scientist who dissents from the “establishment” and fearlessly opposes “political persecution and fraud”.

Either there is a pervasive scientific consensus, in which case contrarians are indeed dissenters, or there is no consensus, in which case contrarian opinions should have broad support within the scientific community and no fearless opposition to an establishment is necessary.

A brief list of other incoherent arguments. Several hundred incoherent pairs of arguments can be found in contrarian discourse. For illustration I mention a few of the remaining ones here: Climate denial is therefore perhaps best understood as a rational activity that replaces a coherent body of science with an incoherent and conspiracist body of pseudo-science for political or psychological reasons.

• Extreme events cannot be attributed to global warming but snowfall disproves global warming.

• Greenland was green but Greenland ice sheets cannot collapse.

• The climate cannot be predicted but we are heading into an ice age.

• Greenhouse effect has been falsified but water vapour is the most powerful greenhouse gas.

• Global warming theory is not falsifiable but it has been falsified.

• My country should not cut emissions first but global warming is natural.

• China needs to cut emissions but global warming is unstoppable.

• Paleo-temperature proxies are unreliable but the middle ages were warmer.

• It is a socialist plot but Nazis invented global warming.

In the eye of the beholder?

In light of this pervasive argumentative incoherence one might ask to what extent it is perceived or recognized as a problem by people who hold contrarian views. This question is difficult to answer with any degree of certainty, although one can attempt to make an inference by examining the 'revealed preferences' of contrarians. In the context of climate change, one way in which preferences might be revealed is by the willingness to incur financial risks to back one’s position in a bet. Bets have a long history as a tool to reveal people’s preferences. Risbey, Lewandowsky, Hunter, and Monselesan analyzed the actual historical and likely future odds of a number of different betting strategies on global temperatures from the late nineteenth century to 2100. Risbey and colleagues found that all possible 15-year bets since 1970 were won by bettors positing continued warming, and that bets against greenhouse warming are largely hopeless now.

It is notable that although contrarians readily claim that the Earth will be cooling in the future, most are unwilling to bet on their stated position. I interpret this to suggest that their public posture differs from their actual knowledge and that they know that any such bet would be hopeless. The unwillingness to bet is thus an indication of the over-arching rationality of denial, notwithstanding its argumentative incoherence.

Conclusion

There is considerable evidence that the rejection of (climate) science involves a component of conspiracist thinking. In this article, I provided preliminary evidence that the pseudo-scientific arguments that underpin climate denial are mutually incoherent, which is a known attribute of conspiracist ideation.

Climate denial is therefore perhaps best understood as a rational activity that replaces a coherent body of science with an incoherent and conspiracist body of pseudo-science for political or psychological reasons.