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.