All posts by Stephan Lewandowsky

Consensus On Consensus

One of the things about the field of climate science that I find particularly striking is the way rigorous debate about so many diverse issues co-exists with a ubiquitous consensus about the fundamental facts that greenhouse gas emissions from our economic activities are warming the planet. Indeed, of all the silly things that have been said about the climate by political operatives and others who cannot accept the 150-year old physics of greenhouse warming for ideological reasons, perhaps the silliest is the claim that scientists do not agree about those fundamental physics.

Anyone who believes that has obviously never been to a meeting of the American Geophysical Union (AGU). I have attended multiple times, and the idea that there is disagreement about greenhouse warming among domain experts is just plainly and completely wrong. There is no kinder way of putting this: the consensus is not a matter of opinion, it’s a matter of fact. And the fact is that I have never heard anyone at an AGU meeting dispute that greenhouse gases are a major contributor to the observed global warming during the last 30-50 years. Nor are there any debates about greenhouse warming during those meetings—as is easily ascertained by perusing the conference program.

Given that recognition of the expert consensus is a gateway belief that determines the public’s attitudes toward climate policies, and given that informing people of the consensus demonstrably shifts their opinions, it is unsurprising that attempts continue to be made to deny the existence of this pervasive expert consensus.

Like other forms of disinformation, this denial of the expert consensus impinges on the public’s right to be adequately informed about the risks it is facing. It is therefore potentially ethically dubious. However, disinformation also provides an opportunity for agnotology—that is, learning from the analysis of mistakes and misrepresentations.

An article appeared today in Environmental Research Letters that takes on the disinformation about the scientific consensus. It is aptly entitled Consensus on Consensus and it is authored by a veritable who-is-who of research on the consensus (myself included).

The essence of the article is encapsulated in the figure below, which shows the expert consensus—measured as the percentage agreement on the fundamental premise that the planet is warming from greenhouse gas emissions—across a large number of studies published during the last decade (for the coding of the observations, refer to the original article).

It is clear that as expertise increases, so does the consensus. And the greater the precision of the data (represented by smaller uncertainty bounds), the higher the consensus.

And if you want to know more, here is a four-minute concise summary of the results of our study:


Most Christians are definitely not terrorists

Human cognition can be exquisitely attuned to our environment, but it can also be subject to numerous strong biases. To illustrate, consider the following logical puzzles:

Some Christians are terrorists. Therefore all Christians are terrorists.

Some Jews are terrorists. Therefore all Jews are terrorists.

Some Muslims are terrorists. Therefore all Muslims are terrorists.

The answer in all cases is a clear and unambiguous no—the inference is not warranted. Notwithstanding the existence of Timothy McVeigh, the Stern Gang, or Osama bin Laden, the inference that all members of their respective faiths are terrorists is entirely invalid.

Yet, depending on one’s background, worldview, and faith, it may be more or less tempting to endorse or reject one or the other of the above puzzles. There is much evidence that people’s reasoning—especially when it comes to accepting scientific findings—is affected by variables beyond logic, in particular worldview and other motivational variables.

The role of those variables was brought into sharp focus by the recent commentary in Nature, authored by me and Dorothy Bishop. Our commentary sought to stimulate discussion about the boundary conditions of transparency and openness. As committed supporters of openness and transparency, we were particularly concerned with how researchers might be protected from harassment that goes beyond legitimate scrutiny, and how such harassment might be differentiated from the legitimate scrutiny that transparency and openness demand.

We therefore stated:

“Orchestrated and well-funded harassment campaigns against researchers working in climate change and tobacco control are well documented. Some hard-line opponents to other research, such as that on nuclear fallout, vaccination, chronic fatigue syndrome or genetically modified organisms, although less resourced, have employed identical strategies.” [Emphasis added]

The public record, sadly, contains ample evidence that opposition to research in those areas goes beyond robust discussion or intense scrutiny, with death threats being received by researchers measuring the fallout from the Fukushima nuclear disaster and by medical researchers working in the area of chronic fatigue syndrome, to cite but two examples.

Bafflingly, this accurate statement has led to considerable invective and accusations on Twitter and on various blogs by critics of chronic-fatigue research. Those critics often appeared to be unencumbered by any acquaintance with what we wrote.

To understand why, let’s revisit the puzzles just discussed:

Some Christians are terrorists. Therefore all Christians are terrorists.

Some Jews are terrorists. Therefore all Jews are terrorists.

Some Muslims are terrorists. Therefore all Muslims are terrorists.

Some hard-line opponents of research on chronic fatigue syndrome overstep the bounds of legitimate discussion. Therefore all opponents of research on chronic fatigue syndrome overstep those bounds.

That last inference is as false as the preceding three.

Accusations that I have “slurred patients” akin to a “racist pig” and that I have compared critics of chronic fatigue research to climate deniers are therefore not only invalid—see here for my detailed thoughts on patients’ rights and how they can and should be protected—but counter-productive.

I have no involvement in research on chronic fatigue, nor do I have any research interest in it. However, I have ample experience in studying the symptoms of pseudoscience and recognizing when an agenda or motivated cognition overpowers reasoned argument.

On the basis of that expertise, it has become quite clear that some (note that crucial word again here: some) opponents of chronic-fatigue research are not engaging in reasoned discourse but are exhibiting all the hallmarks of pseudoscience. The evidence for that is on the public record, in broad daylight, and for all to see who care to look for it.

There are two conclusions that do not follow from this: First, it would be illogical to tar all opponents or critics of chronic-fatigue research with the brush of pseudoscience.

Second, it would be illogical to conclude that just because some opposition to chronic-fatigue research relies on pseudoscience and harassment, that research is thereby vindicated and must be beyond reproach. Perhaps there are problems with some research somewhere, notwithstanding how unreasonable some critics are.

However, given how quickly people can jump to conclusions when it serves their purposes, moderate critics of chronic-fatigue research—who exist as surely as there are people of faith who are not terrorists—ought to consider whether it might not be in their best interest to distance themselves from such rhetoric lest it impair their own credibility.

After all, no one benefits if people are jumping to unwarranted conclusions.

Transparency and Scrutiny vs. Harassment and Intimidation: The Triage

A commentary appeared today online in Nature, co-authored by me and Dorothy Bishop, which took up the issue of transparency in science, with a particular emphasis on the “dark” side of transparency and openness. The article is freely available, and in this post I condense our argument into a few words and then offer some additional issues that are likely to arise during discussion.

Both authors of the commentary are strongly committed to open science: Dorothy made some strong arguments in favor of sharing data here, and I am a co-author of a recent paper on openness published in Royal Society Open Science, which introduced the Peer Reviewers Openness initiative or PRO for short.

However, like many good things such as red wine or healthy dieting, openness and transparency, when taken to an extreme, may also have adverse consequences for the conduct of science. Much has been written—including by me—about the harassment of scientists in contested areas by interminable freedom-of-information (FOI) requests, requests for data when those data are already in the public domain, and so on. A collection of testimonials about such harassment, as well as the need to preserve transparency and openness, arose out of a meeting sponsored by the Royal Society that I organized in June last year: a common thread that emerged from that meeting and the testimonials is the need for a system of “triage” that differentiates legitimate scrutiny and healthy debate from problematic research practices or harassment campaigns that masquerade as scientific inquiry.  

Our commentary proposed a set of “red flags” that can be used to approach this triage. They are not definite criteria but we felt they constitute a worthwhile initial contribution to what will surely be an on-going discussion.

The basic principle underlying our commentary is one of symmetry: while scientists ought to disclose all relevant funding and their data, and while their science must be subject to scrutiny, the same rules ought to apply to critics. For example, if researchers are encouraged to preregister their research and their analysis plan, the same should apply to critics who seek to re-analyze data.  If scientists must disclose their conflicts of interest, why should requestors for data not do likewise?

I find the idea of symmetry self-evidently fair and reasonable. However, that does not mean that everybody will agree: after all, fairness and reason may motivate some critics of scientific work but clearly not all of them. Conversely, while many scientists may openly declare their conflicts of interest, not all of them do, and we may therefore encounter continued resistance to openness.

There are a few specific questions that we touched on in the commentary but did not have time or space to do full justice. I therefore provide some additional thoughts here.

Researchers’ control over their (behavioral or medical) data during reanalysis.

In our commentary we note that “Researchers also need control over how data is to be used if it goes beyond what participants agreed to (for example, analysis of ethnic, race or gender differences in data collected for different purposes).”

What does this mean and is it even enforceable? If I make available a multi-dimensional data set with many variables and someone else wants to do some post-hoc analysis of variables that I didn’t consider, should I, as a researcher, have any control over that?

This question may be best examined in a very concrete, if rather stark, hypothetical context: Suppose I have collected data on a specific cognitive task in an experiment that examined the efficacy of a new training regime. To control for potential covariates, the data set includes numerous demographic variables, including race, gender, political affiliation, and religious denomination. The data are convincingly anonymized and participants have given consent that their data will be made publicly available.

So far, so open and transparent.

Now suppose the Ku-Klux-Klan (which, alas, exists) and the Anti-Muslim-Bigotry League (which likely exists in some form if not by that name) demand access to the data for reanalysis along racial and religious lines.

Did my participants really give consent to have their data used in that manner? Would anyone from a minority group ever again give consent to participate in an ostensibly “harmless” experiment to discover better training techniques if those data can be exploited by a clever post-hoc fishing expedition to score a political point?

To my knowledge, this problem has been largely ignored in the open data debate and it urgently requires attention.

By the way, the problem would be manageable, and the original researcher’s control enforceable, if requestors have to preregister analyses in the same way that the original researchers hopefully did in the first place. (And yes, we should move towards a culture in which pre-registration becomes a strong normative expectation, if not a requirement, of research.)

Do the requestor’s motives matter?

This is another tricky and nuanced issue: if I have made available my data from a potentially controversial research project, does it matter if they are being re-analyzed by someone who is opposed to my results for political or ideological reasons?

At first glance, the answer should be a clear “no, motives should not matter.” If a re-analysis is really driven by ideological motives, then its flaws will be readily identifiable and can be corrected by the usual scholarly means (such as peer-reviewed publications).

There is, however, a problem: Many areas of science that are contentious involve a political component in which the public’s opinion matters a great deal. For example, it matters whether the public supports labeling of genetically-modified (GM) foods, it matters whether the public supports non-smoking policies in public places, and so on. Now, as a rule of thumb, it is fair to assume that the public will not demand political action on any such problem while they perceive there to be scientific disagreement. After all, the tobacco industry famously stated that “doubt is our product” because they knew that the appearance of a scientific disagreement—even where there was none—would forestall tobacco control.

This creates a dilemma for open data that, to my knowledge, has not been satisfactorily resolved: In contested arenas, the motives underlying a request for data do matter because an illegitimate re-analysis can have far-reaching flow-on consequences. Is it really ethical to let the tobacco industry cherry-pick public-health data to death, thereby delaying tobacco control legislation at a huge cost of human lives and health? Not surprisingly, public-health researchers are therefore very concerned about who has access to raw data.

There is no easy resolution to this issue but it is worthy of further discussion and examination.

Do the requestor’s abilities matter?

Setting aside motivation, does it matter who requests data? Should there be a competence criterion? Or are all requestors equal under the transparency umbrella?

At first glance, the answer should again be a clear “ability or competence should not matter,” for the reasons already noted.

There is, however, a problem: what if the data contain information that challenges meaningful anonymization? Suppose the research involves some medical condition that has a social stigma attached to it, and as part of the research many medically-relevant items of information are collected (e.g., the name or post code of the participant’s physician, the participant’s income and profession, and so on).

It is a challenge to anonymize data at that level of granularity—especially if the sample is small or limited to a small geographic area—although various solutions exist, for example through “delinking” of identifying information from research-relevant information. (Even de-linking is not an entirely trivial matter because unless the linking key has been destroyed or is held by another institution, data are not considered anonymized under the U.K. data protection act.)

Supposing the challenges to anonymization have been met, for example by irreversible delinking, then sensitivity of data alone need not—indeed should not—preclude sharing of the data with other researchers working in an institutional framework in which ethical strictures apply and non-disclosure agreements are meaningful and enforceable.

However, should such data be released to Mr. Tom D. Harry who hails from Widgiemooltha and runs a Center for Transparency in his dunny?

On this issue, I come down on a clear “no”. Sensitive medical or psychological data whose anonymization is challenging ought not to be released to people whose facility to keep them confidential cannot be reasonably established. The U.K. Medical Research Council’s guidelines explicitly state: “The custodian [of the data] must ensure that the group [receiving the data] accepts a duty of confidence and protects confidentiality through training procedures, etc, to the same standards as the custodian [my emphasis].”

Mr. Tom D. Harry is unlikely to meet those stipulations, and if he does not, then he ought not to receive the data.

Of course, procedures must be put in place that balance transparency and concerns about violations of privacy in those instances. Arguably, this should not be left to the original researchers—who may have their own ulterior motives—but must be resolved by some independent arbitration process.

The institutional response to harassment

As we note in the commentary, universities have complaints processes for good reasons. However, complaints are also a known tool of harassment that are amply documented in the context of tobacco research.

How can institutions respond? Universities—by law—must not tolerate harassment of academics or students based on race or gender. So why should they tolerate harassment of academics based on contentious science? Once the triage has been conducted and harassment has been identified, the university’s duty of care should naturally extend to offering protection.

This can be achieved in a number of ways that deserve further discussion. One technique, briefly identified in our commentary, is a public declaration of support by the university for an academic and, importantly, for the status of the scientific issue that is being attacked.

A relevant precedent involves the Rochester Institute of Technology, which affirmed the overwhelming scientific consensus on climate change when one of its academics, philosopher Dr. Lawrence Torcello, became the subject of a hate campaign after he published an opinion piece in an online newspaper.

Dr. Torcello summed up the situation thus in an email to me, which I am citing with permission:

“In fact, RIT didn’t just endorse my academic freedom and the scientific consensus on climate change, the statement published by the institute also acknowledged that my work had been misrepresented by certain media outlets, it encouraged people to read my actual piece, and it provided a link to my piece. Additionally, a motion was raised at academic senate to endorse the university’s statement supporting me, which passed unanimously. The dean of my particular college also sent around an official communication to liberal arts faculty condemning the harassment and making faculty aware that his office is prepared to support any faculty harassed for their research. Finally, a generalized version of the statement issued in my defense was placed permanently on the Provost’s website in order to direct any future harassers to the statement. I was consulted and kept in the loop at every stage of the university’s response.  The dean’s office has also offered to help sponsor a conference on such academic harassment. … I think it makes a pretty good case study of how universities ought to respond in such situations.”

Let the conversation continue, without harassment and with an emphasis on transparency, open data, and full disclosure of potential conflicts of interest.

Putting the pause to a blind expert test

A new paper that just appeared online in the Bulletin of the American Meteorological Society examines the idea of a “pause” in global warming in novel ways, including a blind expert test. The paper is authored by Stephan Lewandowsky, James Risbey, and Naomi Oreskes. It is open access and can be found here.

The abstract of the paper is as follows:

There has been much recent published research about a putative “pause” or “hiatus” in global warming. We show that there are frequent fluctuations in the rate of warming around a longer-term warming trend, and that there is no evidence that identifies the recent period as unique or particularly unusual. In confirmation, we show that the notion of a “pause” in warming is considered to be misleading in a blind expert test. Nonetheless, the most recent fluctuation about the longer-term trend has been regarded by many as an explanatory challenge that climate science must resolve. This departs from long-standing practice, insofar as scientists have long recognized that the climate fluctuates, that linear increases in CO2 do not produce linear trends in global warming, and that 15-year (or shorter) periods are not diagnostic of long-term trends. We suggest that the repetition of the “warming has paused” message by contrarians was adopted by the scientific community in its problem-solving and answer-seeking role and has led to undue focus on, and mislabeling of, a recent fluctuation. We present an alternative framing that could have avoided inadvertently reinforcing a misleading claim.


Restoring Recurrent Fury

A peer-reviewed article appeared in print today in an open-access journal that is likely to stimulate some interest and debate:

Lewandowsky, S., Cook, J., Oberauer, K., Brophy, S., Lloyd, E. A., & Marriott, M. (2015). Recurrent fury: Conspiratorial discourse in the blogosphere triggered by research on the role of conspiracist ideation in climate denial. Journal of Social and Political Psychology, 3 (1). doi: 10.5964/jspp.v3i1.443.

The article fits within a fairly large and growing body of evidence that suggests that the rejection of well-established scientific facts, such as the safety and efficacy of vaccinations or the fact that HIV causes AIDS or the fact that CO2 emissions alter our global climate, is often accompanied by conspiracist ideation—that is, the idea that scientists or the government are colluding to create a “hoax”. The “hoax” may involve the link between HIV and AIDS or between smoking and lung cancer or between CO2 emissions and climate change: Denial of scientific propositions involves the same playbook and the same motivated cognition, irrespective of which scientific fact is being targeted.

Our new article reports 3 studies that examined the discourse in the climate-“skeptic” blogosphere in response to an earlier publication in Psychological Science by Lewandowsky, Oberauer, and Gignac (often known as LOG12) which reported a small but significant (and replicable) association between the endorsement of various conspiracy theories and the rejection of climate science. 

Continue reading Restoring Recurrent Fury

Recurrent Fury: Frequently Asked Questions

Q. What is conspiracist ideation?

Conspiracist ideation is a style of thinking, otherwise known as conspiratorial thinking. It refers to a person’s propensity to explain political or social events as a secret plot by powerful individuals or organizations.

Q. How strong is the evidence linking climate science denial with conspiratorial discourse?

A number of studies independently present evidence linking climate science denial with conspiratorial thinking. One well-known paper (Lewandowsky, Oberauer, & Gignac, 2013; referred to as LOG12 from here on) surveyed blog readers, finding a small but statistically significant link between doubts about anthropogenic global warming and conspiratorial thinking. LOG12 inspired the conspiratorial reaction in the blogosphere that is reported in Recurrent Fury.

This result is confirmed by other studies. Another study involved a nationally-representative sample of Americans (Lewandowsky, Gignac & Oberauer, 2013). This analysis replicated the LOG12 finding of an association between climate science denial and conspiratorial thinking. The size of this effect was small when the conspiracy theories being considered were unrelated to scientific propositions–however, the effect was sizable for an item that directly queried whether climate change is a “hoax”: That idea was endorsed by 20% of the sample and it explained 25% of the variance in attitudes towards climate change generally.

An independent study (Smith & Leiserowitz, 2012) found that among people rejecting the findings of climate science, when asked to name the first thing that came to mind regarding climate change, the most common answer was conspiratorial in nature.



Continue reading Recurrent Fury: Frequently Asked Questions

Review of Don’t Even Think About It: Why Our Brains Are Wired to Ignore Climate Change

I recently reviewed George Marhall’s book “Don’t Even Think About It: Why Our Brains Are Wired to Ignore Climate Change” for the National Centre for Science Education. The full review can be found here.

Here, I reproduce the passages from the review that go beyond the scope of a conventional commentary on a book. I tried to articulate what I consider to be one way in which Marshall’s conclusions can be carried forward. Those are subjective considerations and are obviously subject to debate and refinement:

Marshall’s final key point is that in order to ensure a future of dignity for our planet and its inhabitants, we must create a narrative around climate change that invokes “sacred values.”  Sacred values are at the core of our culture: Defending our children is one such sacred value. Likewise, America’s national parks are considered sacred—it’s difficult to imagine that Yellowstone would ever be offered for sale.

I agree with Marshall that moral and ethical values must take centre stage in the response to climate change: It is a question of values and morality whether it is permissible to let Pacific island nations sink below the rising seas. It will come as little surprise that much of the literature on the ethics of climate change considers cutting emissions to be morally mandated. For example, philosopher John Nolt has likened climate change to slavery and racism because it involves the domination of future generations. Those future generations are innocent of any harm to us and do not have a say in their fate, but they are nonetheless bearing the harm from our collective actions that we are now in the position to recognize as being morally wrong.

However, although Marshall opens the door to a powerful moral argument, I felt that he only took a brief peak at the opportunities afforded by his “sacred values”, in a chapter with a collection of brief ideas about how we might “dig us out of this hole.” The underlying tenor of those recommendations is infused with appeals to diversity, openness, and—at least tacitly—a concern with avoiding further polarization.

In my view, those recommendations do not exploit the full power that is offered by the “sacred value” narrative: If our values mandate action on climate change, then we must also recognize that the political and economic forces that are arrayed against such action are violating those values. Although Marshall is well aware of the existence of denial, he stops short of recognizing its full pragmatic and moral import. Many of the environmental narratives that Marshall identifies as having failed, such as the iconic polar bear campaign launched by Greenpeace, failed not just of their own accord but also because the forces arrayed against acting on climate change did their best to make them fail.

If we accept a moral case for climate action, on which I wholeheartedly agree with Marshall, then we must also accept a moral case to tackle organized denial and to understand it for what it is—namely, an endeavor that may (intentionally or not) lead to the domination of future generations in a way not altogether dissimilar from slavery.

Marshall’s stimulating book provides a platform to chart any number of possible future actions. Putting aside political pragmatics, I would extend his work by focusing on sharpening—rather than attenuating— the inevitable and unbridgeable moral conflict between acting on climate change and denying its existence.

The most revered American of the 20th century is Martin Luther King, Jr.

King is universally remembered for leading a movement that was based on the “sacred values” of human dignity, liberty, and equality. It is less well known that Reverend Martin Luther King, Jr. was a polarizing figure.

In his “Letter from Birmingham Jail”—now a highly anthologized masterpiece—in which he responded to his “moderate” critics’ call for patience, King made it quite clear that polarization around his views was not only inevitable but also necessary to achieve his goals. King’s recognition that “justice too long delayed is justice denied” takes on particular meaning in the context of climate change, where delay (of mitigation) is tantamount to denying not just justice but the very livelihood of millions of people who may be displaced by climate change.

Polarization is unfortunate, uncomfortable, and discomforting. But when a U.S. Senator writes a book that refers to climate change as a “hoax” and a “conspiracy”, then that polarizing act does not call for acquiescence or compromise, but for the recognition that polarization may be an inevitable consequence of a conflict between core human values. The nuances of cultural cognition that Marshall so ably reviews may explain polarization but they cannot overcome it by the niceties of “reframing” and “culturally-appropriate” messengers alone.

Australian Professor of Ethics Clive Hamilton recognized this some time ago when he issued a call for environmental radicalism and noted that the future battle over climate change will not be a place for the faint-hearted. It is indeed difficult to conceive of a solution to the climate challenge that will sidestep polarization and—quite probably increasingly ugly—political and ideological battles. Like the civil rights movement of the 1960’s, those battles may require deep courage rather than nuanced cognition about whether polar bears are a good icon for climate “communication.”

Moral and political courage are not without precedent in American politics: Another one of the most revered Americans of the 20th century is President Franklin Delano Roosevelt. In an address at Madison Square Garden in 1936, President Roosevelt noted that “Government by organized money is just as dangerous as Government by organized mob. Never before in all our history have these forces been so united against one candidate as they stand today. They are unanimous in their hate for me.”

In a highly polarizing gesture Roosevelt famously added: “and I welcome their hatred.”

Perhaps we need to fear the fear of polarization more than polarization itself.

Voices from the climate community on “seepage”

Our recent article “Seepage: Climate change denial and its effect on the scientific community” in Global Environmental Change, authored by me and Naomi Oreskes, James S. Risbey, Ben R. Newell, and Michael Smithson, has attracted a bit of attention over the last few days. I sample a few comments here and reply to a lengthy post by Richard BettsHead of the Climate Impacts strategic area at the UK Met Office, that critiqued our paper.

The Vice Chair of the IPCC Jean Pascal van Ypersele tweeted about our paper and encouraged climate scientists to read it:


Some scientists clearly did, and sent us some comments for attribution:

Professor Andrew Dessler, of Texas A&M, stated:

“These results strike a chord with me.  As someone working in the area of climate change, I have been attacked for my public statements about the science of climate change.  I can’t help but think that this causes me to water down what I say.”

Professor Stefan Rahmstorf of the Potsdam Institute for Climate research (PIK) provided the following comment:

“The paper on “seepage” by Lewandowsky et al provides sobering and convincing evidence for how climate change denial affects the scientific community – this should make every climate scientist pause and think. The authors highlight an important problem: how climate scientists have been influenced in their work by the public debate, to the extent of even inadvertently adopting a rhetorical framing created by contrarian voices from outside science.  They show this for the example of the supposed (but not real) “pause” or “hiatus” in global warming, for which some of us have been using the label “faux pause” for years (check out #fauxpause on twitter).
They highlight how the IPCC adopted the term ‘hiatus’ despite strong concerns by the German government about the misleading nature of this term. And they analyse the double standards used when discussing the so-called ‘pause’ as compared to an equally long period of rapid warming, which in fact deviated more from the long-term trend than the recent phase of slower warming. In fact, in 2007 in Science we noted the rapid warming during 1990-2006, naming as the first reason “intrinsic variability within the climate system” – which is also the prime reason for the slower warming trend when looking at the period starting in the hot outlier year 1998.

As Lewandowsky et al write: “The use of a single ‘cherry-picked’ outlying year to establish the presence of a ‘pause’ … does not conform to conventional statistical practice and is testament to the degree to which the climate mainstream has embraced the ‘pause’ meme for extra-scientific reasons.” I hope that the article by Lewandowsky et al will be widely read and discussed and that it will lead to greater self-awareness in the climate science community in future!”

A post by Katherine Bagley at Inside Climate News reports the impressions of Kevin Trenberth, an IPCC Lead author as follows:

Climate denial campaigns “can absolutely influence what you do and what you write about,” said Trenberth, who was not involved in the study. “Part of the reason they do it is to distract you and get you to waste your time.” Instead of “publishing the good science needed to advance our understanding of climate change,” scientists are left defending their work and debunking false claims.

Those three voices support our analysis that climate denial can affect scientists and how they conduct and communicate their science. At least tacitly, they also recognize that the relevance in our work is not only in pointing out the existence of a phenomenon, but that in so doing we also provide the tools to address it: We know from related work (on which I may blog later) that knowing about a phenomenon such as seepage is half the battle to avoid its occurrence.

Knowledge is generally empowering, and seepage is no exception. Exercising some caution and reflection goes a long way to ensure that one’s scientific agenda is not inadvertently shaped by false agendas.


A Critical Voice: Richard Betts on “seepage”


However, not unexpectedly, there are also some critical voices. We expected that our paper would evoke some spirited disagreement, and so Richard Betts’ critique of our paper is most welcome as it provides us with an opportunity to restate our argument and address some of the objections raised by Professor Betts. To facilitate discussion, I begin by noting that there is much in Betts’s post that we can agree with—for example, the increased role of social media, the increased focus by governments on the need for adaptation and hence decadal predictions. No disagreement there. But then again, none of those points pertain to the issue of seepage.

As far as the core of his objection to the seepage notion is concerned, Betts focuses on our arguments surrounding the alleged “pause” in global warming during the last 15 years. We consider this phase to be a fairly unremarkable fluctuation about the average warming rate, a position we support by some informative statistics.

Our argument about seepage and the “pause” rests on two principal points, namely (a) that this “pause” was given undue attention by the scientific community in comparison to previous episodes of above-average global warming, and (b) that this attention sometimes involved an unexplained—and unjustified—departure from long-standing scientific practice.

I limit myself here to Betts’s comments pertaining to our case study, involving the “pause” in global warming. Unfortunately it appears that Betts’s critique was largely unencumbered by acquaintance with what we actually wrote. I therefore provide specific pointers to our paper that correct his claims.

1. Claim: Lewandowsky et al. “… do not specifically identify the “previous occasions when decadal warming was particularly rapid”, but it’s fair to assume that they are referring to the 1990s, probably the period 1992-1998. This was the most recent occasion when global mean temperatures rose rapidly for a few years…”

  • Neither assertion is correct. Figure 2 in our paper (bottom panel) identifies the period of particularly rapid warming that we were talking about, which spans 1992 to 2007. It follows that 1992-1998 was not the most recent period of rapid global warming, but that very rapid warming was observed in the 15-year period up to 2007.       


2. Claim: “It is perplexing that Lewandowsky et al do not seem to be aware of this [earlier] research on short-term climate variability….. Possibly Lewandowsky et al are wondering why there was not a raft of papers specifically focussing on the observed temperature record between 1992 and 1998. The reason is simple  this was not a particularly surprising event. When global temperatures rose rapidly few a few years after 1992, this was very easily explained by the tailing-off of the short-term cooling influence of the Mount Pinatubo eruption.”

  • The focus on a 7-year time period that we never mention in the paper is perplexing indeed. The 15-year periods we cover are not all readily explained by Mt Pinatubo or the 1998 El Niño.

3. Claim: “Lewandowsky et al regard research into natural variability as “entertaining the possibility that a short period of a reduced rate of warming presents a challenge to the fundamentals of greenhouse warming.” Is there any evidence at all of climate scientists actually thinking this? I don’t think so.”

  • Yes, there is evidence that scientists frame it as a fundamental challenge (even if they don’t actually believe that). Consider the following verbatim statements from recent articles on the “pause:”

“Despite ongoing increases in atmospheric greenhouse gases, the Earth’s global average surface air temperature has remained more or less steady since 2001.”

“Despite a sustained production of anthropogenic greenhouse gases, the Earth’s mean near-surface temperature paused its rise during the 2000–2010 period.”

“Given the widely noted increase in the warming effects of rising greenhouse gas concentrations, it has been unclear why global surface temperatures did not rise between 1998 and 2008.”


“Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming.”

And the list goes on….

What those citations show is that a short-term fluctuation, sometimes over as short a period as a decade, was considered by those scientists to constitute a “problem” for climate science that had to be resolved.

To restate what James Risbey already noted in a comment on Betts’s post:

“In the past, the notion that CO2 and GMST must increase in lockstep was considered laughable and indicative of one’s ignorance of climate.  It was well known that CO2 is increasing steadily, but GMST does not because of decadal and longer scale variability.  Yet in recent years, some prominent climate research papers on the so called ‘hiatus’ have started out by pointing to an apparent conundrum between steadily increasing CO2 and fluctuating GMST.  i.e. that which was not a conundrum now is.  That change in framing is indicative of ‘seepage’. That’s not a particularly controversial claim or complicated argument, but it is a different argument from the one addressed by Richard on trends in climate variability research.”

Of course, all papers on the “pause”, including those cited above, come to the conclusion that anthropogenic global warming continues and will continue to pose a risk in the future. In addition, those papers have contributed to our knowledge of short-term climatic variability. Contrary to another claim made by Betts, we are conversant with that research and have recently contributed to it by showing that climate models do accommodate recent temperature trends when the phasing of natural internal variability is taken into account—as it must be in comparing a projection to a single outcome. However, notwithstanding the “pause” papers’ conclusions and the fact that global warming continues unabated, the framing of a short-term fluctuation as a problem for science departs from long-standing stastistical and climatological knowledge.


The Risks of Risk Communication

At this point, one might wonder why all this matters? Given that we do not disagree with the results of the research on the faux “pause”—how could we, having contributed to it—and given that the disagreement between Betts and us seems to boil down primarily to semantics and the imputation of scientists’ motivations, does it matter whether or not there is “seepage” into the scientific community?

We believe it matters a great deal.

To be perfectly clear: Talk of a “hiatus” or a “pause” in global warming has been a contrarian talking point for about a decade, and there is clear evidence that this framing was picked up by the media (see Max Boykoff’s article in Nature Climate Change last year) and has now been picked up by some climate scientists.

This matters because political momentum for mitigative action is difficult to sustain or mount while the public believes that there is a “pause” in global warming. Talk of a “pause”, when there is none, therefore has political consequences and, by implication, also carries ethical risks.

Lest one think that this risk is remote, the legal aftermath of the earthquake in L’Aquila, which embroiled scientists in charges of manslaughter for their alleged failure to warn the community, vividly illustrates the legal and moral hazards that are incurred when the public is not informed (or misinformed) of the full envelope of identifiable risks arising from scientific findings.

Seepage: The effect of climate denial on the scientific community

The article “Seepage: Climate change denial and its effect on the scientific community” just appeared in Global Environmental Change. The article is authored by me and Naomi Oreskes, James S. Risbey, Ben R. Newell, and Michael Smithson.

It is open access and can be found here.

Seepage: The Executive Summary

We initiate our argument with the known fact that vested interests and political agents have long opposed political or regulatory action in response to climate change by appealing to scientific uncertainty. We know from earlier work that uncertainty is no cause for inaction—on the contrary, greater scientific uncertainty should make us worry more, not less, about the potential consequences of climate change. Alas, those actual scientific implications are often inverted in public discourse where uncertainty often invites wishful thinking and hence inaction. In this new article, we examine the effect of contrarian talking points that arise out of uncertainty on the scientific community itself. We show that although scientists are trained in dealing with uncertainty, there are several psychological and cognitive reasons why scientists may nevertheless be susceptible to uncertainty-based argumentation, even when scientists recognize those arguments as false and are actively rebutting them.

Climate scientists have done an admirable job pursuing their science under great political pressure, and they have tirelessly rebutted pseudoscientific arguments against their work. Nonetheless, being human, scientists’ operate with the same cognitive apparatus and limitations as every other person. In consequence, it is important to be aware of the factors that may cause scientists to take positions that they would be less likely to take in the absence of outspoken public opposition. We refer to this phenomenon as seepage.

We highlight three well-known psychological mechanisms that may facilitate the seepage of contrarian memes into scientific discourse and thinking: ‘stereotype threat’, ‘pluralistic ignorance’ and the ‘third-person effect’.

Stereotype threat refers to the emotional and behavioural responses when a person is reminded of an adverse stereotype against a group to which they belong.  Thus, when scientists are stereotyped as ‘alarmists’, a predicted response would be for them to try to avoid seeming alarmist by downplaying the degree of threat. There are now several studies that highlight this tendency by scientists to avoid highlighting risks, lest they be seen as ‘alarmist.’ 

Pluralistic ignorance describes the phenomenon which arises when a minority opinion is given disproportionate prominence in public debate, resulting in the majority of people incorrectly assuming their opinion is marginalized.  Thus, a public discourse that asserts that the IPCC has exaggerated the threat of climate change may cause scientists who disagree to think their views are in the minority, and they may therefore feel inhibited from speaking out in public.

Finally, research shows that people generally believe that persuasive communications exert a stronger effect on others than on themselves: this is known as the third-person effect.  However, in actual fact, people tend to be more affected by persuasive messages than they think.  This suggests the scientific community may be susceptible to arguments against climate change even when they know them to be false.

While those potential drivers of seepage are well-understood outside the context of climate science, it is a different matter to show that they have actually affected the conduct of science. In our article, we illustrate the consequences of seepage from public debate into the scientific process with a case study involving the interpretation of temperature trends from the last 15 years, the so-called ‘pause’ or ‘hiatus’. This is a nuanced issue that can be addressed in multiple different ways. In this article, we focus primarily on the asymmetry of the scientific response to the so-called ‘pause’—which is not a pause but a moderate slow-down in warming that does not qualitatively differ from previous fluctuations in decadal warming rate. Crucially, on previous occasions when decadal warming was particularly rapid, the scientific community did not give short-term climate variability the attention it has recently received, when decadal warming was slower. During earlier rapid warming there was no additional research effort directed at explaining ‘catastrophic’ warming. By contrast, the recent modest decrease in the rate of warming has elicited numerous articles and special issues of leading journals and it has been (mis-)labeled as a ‘pause’ or ‘hiatus’.  We suggest that this asymmetry in response to fluctuations in the decadal warming trend likely reflects the ‘seepage’ of contrarian memes into scientific work.

Finally, we offer ways in which the scientific community can detect and avoid such inadvertent seepage.

Seepage: Some FAQs

There are a few questions one might reasonably ask about our article, and we start by addressing some of those below. We may follow up with additional posts as the discussion evolves:

1. What is seepage?

  • The inadvertent intrusion of memes that arose outside the scientific community into scientific discourse and thinking. There are two criteria for the detection of seepage: First, the scientific community has adopted assumptions or language that originated outside the scientific community or in a small set of dissenting scientific voices. Second, these assumptions depart from earlier norms and scientific conventions.
  • Although scientific conventions may occasionally change as theorizing evolves, in the case of seepage explicit conceptual rationale or empirical support for a departure from previous norms is lacking or weak.

2. How does seepage work?

  • There are a number of known psychological and cognitive variables that provide the opportunity for seepage. We focus on three: Stereotype threat, pluralistic ignorance, and the third-person effect.

3. What effects does seepage have?

  • At a minimum, seepage arises when scientists adapt linguistic frames that were created outside the scientific community for political purposes. We use the case of the so-called “pause” in global warming, which should not be called a pause or hiatus given that global warming continues unabated. Ironically, seepage can arise even when scientists are rebutting a contrarian meme but are nonetheless framing the problem in a way that is inappropriate or misleading.
  • At worst, seepage may alter the way in which scientists interpret data. This arises when they depart from long-standing and long-accepted practice in response to contrarian memes (for example, by entertaining the possibility that a short period of a reduced rate of warming presents a challenge to the fundamentals of greenhouse warming.)

4. Is the research on the “pause” wrong?

  • No. On the contrary, irrespective of the framing chosen by their authors, all articles on the pause have reinforced the reality of global warming from greenhouse gas emissions, and this body of work has yielded more knowledge of the processes underlying decadal variation. None of this work has come to the conclusion that the physical processes underlying global warming are somehow in abeyance or that prevailing scientific conceptions of them are incorrect.
  • However, by accepting the framing of a recent fluctuation as a ‘pause’ or ‘hiatus’, research on the pause has, ironically and  unwittingly,  entrenched the notion of a ‘pause’ (with all the connotations of that term) in the literature as well as in the public’s mind. Some of that research may therefore have inadvertently misdirected public attention.

5. Who is responsible for seepage?

  • There is abundant evidence that climate science is subject to intense scrutiny and hostility from vested interests. Much is known about how those attacks on climate science take place and the funding that is devoted to those attempts to undermine science.
  • There is also evidence that media coverage surrounding climate change is often misleading and that some media organs disseminate falsehoods routinely, thereby denying the public the right to be accurately informed about risks from climate change.
  • Climate scientists have devoted much time and energy to rebutting those contrarian arguments (often called “zombie” arguments because of the number of times they have already been rebutted).
  • For the reasons outlined in our paper, climate scientists may nonetheless not be immune to (unwittingly) adapting to contrarian framing, for example by talking about a “pause” when there is none.

6. How do we eliminate seepage?

  • Knowing about the potential for seepage is half the battle. For example, there is evidence that merely being aware of the operation of stereotype threat is sufficient to limit its adverse consequences. Our paper lists a few further factors that may be helpful.
  • In addition, scientists need to remember that the purpose of contrarian memes is to keep the controversy alive. While it is a scientist’s job to answer genuine scientific questions, getting pulled into contrarian linguistic frames helps maintain the fiction that the science is still riven with fundamental equivocations and therefore too uncertain to form a reliable basis for public policy. Awareness of this fact is crucial for scientists to resist seepage.

The robust relationship between conspiracist cognition and rejection of (climate) science

There are two articles in Psychological Science that appeared online today: The first article by Ruth Dixon and Jonathan Jones presents an alternative analysis of two papers that I published with colleagues in 2013 on the role of conspiracist ideation in the rejection of science. The second article is a rejoinder to Dixon and Jones and is authored by me together with Gilles Gignac and Klaus Oberauer.

We are very pleased that, more than two years after the first article in Psychological Science became available, a critical commentary on our work was submitted for peer review. This is the type of scientific debate that moves the field forward, unlike some of the other responses to our work, detailed here, that have only wasted our time and that of other university staff without anything to show for it.

So how did the field move forward by the two sets of articles that appeared today? Opinions will likely be divided on this question, but in our view the alternative analyses of our data by Dixon and Jones underscored the robustness of our original results.

The case that we make in our rejoinder is somewhat nuanced, but in a nutshell Dixon and Jones showed that the correlation between endorsement of conspiracy theories and the rejection of climate science (they did not consider the other scientific propositions that were of interest in our research) will become statistically non-significant under certain circumstances, if the data analyst makes particular choices. We do not question their result per se (we get the same results if we apply their technique), but we argue that the choices that are necessary for this correlation to “disappear” are inadvisable.

  • Dixon and Jones (D&J from here on) dismiss one of our studies because the sample was skewed. We agree that the sample was skewed, but because we were aware of this aspect of our data, we used a data analytic technique—an ordinal rank-based structural equation model—that was unaffected by the presence of the skew. We therefore do not believe that a wholesale dismissal of the study is justified.
  • D&J did not model the full variance-covariance structure of the data, as we did in both studies, but resorted to bivariate linear regression involving a single pairwise relationship between two variables while ignoring all others. Linear regression is known to be susceptible to attenuation through measurement error, and it is therefore not surprising that D&J report associations that are only 1/3 the magnitude of those in our—measurement-error free—analysis. Our view is that if techniques exist for precise assessment of relationships then those techniques should be preferred over tools that are known to reduce the signal-to-noise ratio.
  • D&J further removed 35 respondents from our second study with a representative sample because they responded “neutral” on all items involving the two variables of interest. This has no effect on the association between endorsement of conspiracy theories and the rejection of climate science in the structural-equation model (that’s the tool that is known to be free of measurement error), but it does render the bivariate correlation non-significant. In our opinion, the removal of participants on ad hoc grounds (i.e., looking at the data to identify observations that are deemed unsuitable) represents one of the degrees of freedom available to researchers that has recently been identified as a potentially “questionable research practice”, and we believe that the elimination of observations must therefore be approached with great care. This is particularly true in the case of our study, whose sampling plan was “de facto” pre-registered: That is, we contracted with a professional survey company ( to obtain a representative sample of Americans of a pre-determined size, and to include only those respondents who completed all items and passed an attention filter question. Those were a priori constraints on our sampling plan, and once we obtained the data, we analyzed them all. Of course, one can now stipulate any number of criteria to eliminate observations, but any such ad hoc elimination can be critiqued as a potentially questionable research practice
  • D&J furthermore reverse the role of the dependent and independent variables in their bivariate analysis, whereupon the observed association disappears. To clarify, instead of predicting the attitude towards science from conspiracist ideation, they predict the latter based on the endorsement of climate science. Now, the fact that the results differ between those two statistical models is not surprising because the two models answer different questions. The question we asked is: Do people with a relatively stable disposition to endorse various conspiracy theories (we know that those cognitive attributes are quite stable) tend to reject established scientific propositions? We have a good theoretical reason for asking this question. A person prone to accept conspiratorial thinking may find it easier to explain away the scientific consensus as arising from a conspiracy among scientists. Indeed, this possibility is supported by a large body of research. The question asked by a statistical model reversing the direction of prediction is: Do people who reject established scientific propositions tend to endorse all sorts of conspiracy theories? We see no theoretical rationale for why one’s attitude towards specific scientific claims should influence one’s general tendency to endorse thematically unrelated conspiracy theories. D&J provide no theoretical rationale for their reversal of the roles of predictor and predicted variable either.

In summary, we are pleased that our work has finally been critiqued in the appropriate forum—namely, the peer-reviewed literature. We profited from this exchange because it forced us to consider our data in new and different ways, and in so doing we were able to show how robust our results are to a number of choices that data analysts might legitimately make. It is only under a fairly specific concatenation of such choices—all of which we believe are sub-optimal—that one of the many associations between variables reported in our paper becomes non-significant.

There is, moreover, one clear point of agreement between us and D&J: The association between conspiracist cognition and the rejection of climate science is relatively small in magnitude. Indeed, the effect explains only about 4% of the variance in our structural-equation models, compared to more than 60% that is explained by endorsement of “free-market” economics. However, just because an effect is small does not mean it is inconsequential: there are several well established and highly consequential effects that are as small as, or smaller than, our reported association. For example, the correlation between combat exposure and post-traumatic stress disorder, and between lead exposure and children’s IQ, explain in the order of only 1% of the variance. They nonetheless have notable public-health implications once scaled up to society as a whole.