New publication: Does it matter if the consensus on anthropogenic global warming is 97% or 99.99%?

New publication: Does it matter if the consensus on anthropogenic global warming is 97% or 99.99%?

Cross-posted at Skeptical Science

The 97% consensus on anthropogenic global warming (AGW) reported by Cook et al. (2013) (C13) is a robust estimate. Alternative methods, such as James Powell’s, that identify only explicit rejections of AGW and assume that all other instances are endorsements, miss many implicit rejections and overestimate the consensus.

The C13 method can be modified and used to estimate the consensus on plate tectonics in a sample of the recent geological literature. This limited study—not surprisingly to anyone familiar with the field—produces a consensus estimate of 100%. However, among the abstracts that expressed an opinion. only implicit endorsements of the theory were found: this underlines the importance in consensus studies of identifying implicit statements. The majority of the abstracts expressed no position. Assuming that these cases suggest either uncertainty about, or rejection of, plate tectonics (as some critics of C13 have claimed about AGW) would lead to the absurd conclusion that the theory is not widely accepted among geologists.

Opinion surveys show that the public is misinformed about true state of consensus among climate scientists, with only a minority aware that it is greater than 90%. The difference between 97% and 99.99% is tiny compared to this gap. The 3% of published papers that reject AGW are contradictory and have invariably been debunked. They do not therefore provide a coherent alternative account of climate science. Despite this, dissenters are awarded disproportionate attention by ideologically and commercially motivated interests, as well as by false balance in the media. Countering this public confusion requires both communicating the consensus and debunking bad science.

For a shorter summary than the one below, read Dana Nuccitelli’s Guardian piece: Is the climate consensus 97%, 99.9%, or is plate tectonics a hoax? Continue reading

Carbon budgetting

Carbon budgetting

Originally published online at Corporate Knights Magazine on May 18, 2016 and in the hardcopy magazine in June 2016.

The Paris Agreement on mitigating climate change seeks to limit emissions with the goal of holding the increase in the global average temperature to well below 2 C above preindustrial levels while also pursuing efforts to limit the temperature increase to 1.5 C.

As with any complicated international deal, the devil is in the language. While it acknowledges that developing countries will take longer to peak their greenhouse gas emissions, it agrees that these reductions will be made on the basis of equity.

parisagreement1

This phrasing, “basis of equity,” probably means very different things to different parties to the agreement. The Kyoto Protocol adopted in 1997 was based on the principle of “common but differentiated responsibility,” which is to say that developed countries, with their disproportionate historic responsibility for past emissions, were expected to cut sooner and deeper. This same language is still used in the Paris Agreement reached last year. Continue reading

Consensus on Consensus

Consensus on Consensus

Originally published in Corporate Knights Magazine

studies_consensus

In 1998 and 1999, American scientists Michael Mann, Raymond Bradley and Malcolm Hughes published two papers that reconstructed the average temperatures of the northern hemisphere back to the year 1000. The articles showed a temperature profile that gently declined from 1000 to 1850, fluctuating a little along the way, with a sudden increase in the late nineteenth and the twentieth centuries.  The graph was nick-named “the Hockey Stick”, with its long relatively straight handle showing the stable pre-industrial climate and the blade representing the sudden uptick in the last 150 years.

The diagram was a striking depiction of the abrupt warming that had occurred since the Industrial Revolution compared to what happened before. For those opposed to the scientific consensus on Anthropogenic Global Warming (AGW), the Hockey Stick posed a threat and had to be broken. Continue reading

James Powell is wrong about the 99.99% AGW consensus

James Powell is wrong about the 99.99% AGW consensus

In a recent article in Skeptical Inquirer, geologist and writer James Lawrence Powell, claims that there is a 99.99% scientific consensus on Anthropogenic Global Warming (AGW). You might think that after all of the harsh criticism that the 2013 Cook et al. paper (C13) has received from climate contrarians that we would be pleased to embrace the results of a critique that claims we were far too conservative in assessing the consensus. While it certainly does make a nice change from the usual rants and overblown methodological nit-picks from the contrarians, Powell is wrong to claim such a very high degree of agreement.

He makes many of the same errors that contrarian critics make: ignoring the papers self-rated by the original authors; and making unwarranted assumptions about what the “no-position” abstracts and papers mean.

Powell’s methodology was to search the Web of Science to review abstracts from 2013 and 2014. He added the search term “climate change” to the terms “global climate change” and “global warming” that were used by C13.  He examined 24,210 papers co-authored by 69,406 scientists and found only five papers written by four authors that explicitly reject AGW. Assuming the rest of the abstracts endorsed AGW, this gives consensus figures of 99.98% (by abstract) and 99.99% (by author).

His definition of explicit rejection would align roughly with the seventh level of endorsement used in C13: “Explicitly states that humans are causing less than half of global warming” . In the abstracts from 1991-2011, C13 found 9 out of 11,914 that fit level 7, which using Powell’s consensus calculation assumptions, would yield 99.92%. So, there is probably not much difference between the two approaches when it comes to identifying an outright rejection paper. It’s what you assume the other abstracts say—or do not say—that is the problem.

C13 also counted as “reject AGW” abstracts that: “Implies humans have had a minimal impact on global warming without saying so explicitly, e.g., proposing a natural mechanism is the main cause of global warming”. These are more numerous than the explicit rejections and include papers by scientists who consider that natural causes are more important than human causes in recent warming, but who do not outright reject some small human contribution.

pacmen2

Competing Climate Consensus Pacmen. Cook on the left, Powell on the right.

Continue reading

Unsure about how to talk about uncertainty? Read this

2015-07-05_15-39-46Adam Corner, Stephan Lewandowsky, Mary Phillips, and Olga Roberts have today published The Uncertainty Handbook, which is a twenty-page practical guide for climate communicators. It is excellent, clearly written and I recommend that everyone read it all. Adam Corner has a blogpost outlining the Handbook at Shaping Tomorrow’s World.

As the authors say, everyone is already familiar with making decisions under uncertainty. To make plans means accepting that they may not unfold as expected. The natural world is chaotic, with many known-unknowns and unknown-unknowns. The human world is even more unpredictable. We all develop rules-of-thumb to deal with everyday uncertainty: whether to take an umbrella, when to take a vacation, whose advice to trust. But we humans do not always have good instincts when it comes to grasping the uncertainty of novel and unfamiliar situations. As Daniel Kahneman showed in his masterpiece Thinking, Fast and Slow we are often not very smart when confronting probability or logic problems in our lives, especially when they are expressed numerically.  The Economist reviewer wrote:

In one experiment described by Mr Kahneman, participants asked to imagine that they have been given £50 behave differently depending on whether they are then told they can “keep” £20 or must “lose” £30—though the outcomes are identical. He also shows that it is more threatening to say that a disease kills “1,286 in every 10,000 people”, than to say it kills “24.14% of the population”, even though the second mention is twice as deadly. Vivid language often overrides basic arithmetic.

Framing is everything.

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You can now run a MOOC at your own pace, from July 1

The Denial 101x MOOC (Massive Open Online Course) was a great success, with thousands of participants and many satisfied students. I admit that I was quite touched by the mostly positive student reactions and I am thankful to John Cook for inviting me to contribute to this course in a small way. This video compilation of students’ feedback shows how people from diverse backgrounds all got something from the course.

From July 1, 2015 onwards, the course is available for anyone to follow at their own pace. It’s completely free of charge, naturally!

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Why the 97 per cent consensus on climate change still gets challenged

Here are some excerpts from an article I wrote  for the magazine Corporate Knights, that was published on May 14, 2015. Some references and links have been added at the end. This is cross-posted with Skeptical Science.

In 2004, science historian Naomi Oreskes published a short paper in the journal Science concluding there was an overwhelming consensus in the scientific literature that global warming was caused by humans.

After the paper’s release, there was some unexpectedly hostile reaction. This prompted Oreskes and her colleague Erik Conway to go even deeper with their research, leading to the publication of the book Merchants of Doubt. It documents how a small group of scientists with links to industry were able to sow doubt about the scientific consensus and delay effective policy on DDT, tobacco, acid rain and, now, global warming.

Fast forward to two years ago: a team of volunteer researchers (myself included) associated with the website Skeptical Science decide to update and extend Oreskes’ research. Led by University of Queensland researcher John Cook, we analyzed the abstracts of about 12,000 scientific papers extracted from a large database of articles, using the search terms “global warming” and “global climate change.” The articles had been published over a 21-year period, from 1991 to 2011.

As an independent check on our results, we also sent emails to the more than 8,500 scientist authors of these articles. (These were the scientists whose e-mail addresses we were able to track down). We asked them to rate their own papers for endorsement or rejection of man-made global warming.

Both approaches yielded a very similar result: 97 per cent of the scientific literature that expresses an opinion on climate change endorses the expert consensus view that it is man-made. The results were published in May 2013 in the journal Environmental Research Letters.

We were astonished by the positive reception. Mention of the paper was tweeted by U.S. President Barack Obama, Al Gore and Elon Musk, among others. Obama later referenced it in a speech at the University of Queensland, while U.S. Secretary of State John Kerry has referred to the 97 per cent consensus in recent speeches. John Oliver based an episode of his HBO comedy show Last Week Tonight around it, a clip viewed online more than five million times.


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Have we turned the corner on emissions?

One of these days, the world will get its act together and halt the growth in CO2 emissions. This week, the International Energy Agency reported that the rise in emissions did indeed stall in 2014. According to the announcement, this was the first time in forty years that IEA emissions did not increase, except in years of economic weakness.

When we start to turn the emissions corner for good, this is what it will look like. Although halting emissions growth does not yet put us on the path to meeting the 2°C target, it does at least mean that we might not be destined to follow the business-as-usual path to disaster along the worst-case RCP8.5 pathway. At least we are not going as fast along that road.

Chris Mooney, Climate Nexus and Joe Romm have articles on this, all worth reading.

The IEA announcement was a teaser: we are going to have to wait until June 15, 2015 to see the details of the analysis. In the meantime, I thought it would worthwhile looking at some data to see how confident we can be that this really is a positive signal that we can discern out of the noise and uncertainty.

First, let’s plot year-to-year growth in CO2 emissions, along with global GDP growth, against time:

IEA1

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Does providing information on geoengineering reduce climate polarization?

This article was originally published at Skeptical Science on March 4, 2013.

Dan Kahan of Yale University and four colleagues have just published an article in Annals of the AAPS titled: Geoengineering and Climate Change Polarization Testing a Two-Channel Model of Science Communication that investigates the effect on study participants’ attitudes to climate change after reading an article about geoengineering. In their abstract, they write:

We found that cultural polarization over the validity of climate change science is offset by making citizens aware of the potential contribution of geoengineering as a supplement to restriction of CO2 emissions.

I will argue here that this experiment achieved no such result because the premise was wrong. Specifically, the information on geoengineering that was presented to the study participants (in the form of a fictional newspaper article) bears no relation to mainstream scientific opinion on geoengineering nor, even, to the opinions of advocates of geoengineering. Geoengineering is portrayed in the fictional newspaper article as a strategy with no uncertainty about how well it might work and, it is claimed, will “spare consumers and businesses from the heavy economic costs associated with the regulations necessary to reduce atmospheric CO2 concentrations to 450 ppm or lower”. This is hardly depicting geoengineering as a “potential solution” or “a supplement” to the restriction of emissions, as is claimed in the abstract of the paper.

In fact, what Kahan et al. have demonstrated is that presenting misinformation dressed up as fact can affect people’s opinions about climate change. That may be interesting as a social science experiment conducted on consenting adults, but it is not much use as a guide to effective public science communication, constrained as it is to tell the truth.
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Consensus, Criticism, Communication

Thanks in good part to our critics, our paper Quantifying the consensus on anthropogenic global warming in the scientific literature keeps getting more attention. It almost seems that you can’t open up a browser without seeing the “97%” meme somewhere. The extra interest prompted by Richard Tol’s recent critical article has maintained the rate of downloads of the paper at 500 per day and has pushed the total to nearly 200,000. The recent buzz has also spurred discussions on And Then There’s Physics, Variable Variability, Twitter, in The Guardian and a renewed line of criticism in a series of articles by Yale University Professor Dan Kahan.

I was surprised—a little shocked even—at some reactions to the release of our consensus paper. I was prepared, of course, for an angry response from those people who maintain that the expert consensus on the basics of anthropogenic climate change is either non-existent or crumbling. But my colleagues and I were never expecting to change their minds.

However, strong and sharply-worded opposition was unexpected from people like Dan Kahan (sarcasm), Mike Hulme (“infamous”), some journalists (“unwarranted attention”) and some climate scientists (satire), none of whom actually dispute the existence of an expert consensus on the basics of anthropogenic climate change. That the criticism often seemed tinged with peevishness (at least before they did some back-tracking) was especially surprising. I never saw our work as in any way undermining their approaches and analyses, but rather complementing them. And the complaints continue.

To give you a flavour of the nature of the recent discourse, here are some Tweets. (Keywords: Haha, doesn’t work, distraction, diversion, Sad, don’t inform, They insult, psychological control):

2014-06-21_18-24-49

The apparent anger and the throw-everything-at-the-wall criticism suggest that this is something other than a measured scholarly critique. Let’s first look at the main strands of argument in a bit more detail. Continue reading

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