On last week's BBC show Sunday Politics, Andrew Neil hosted UK Energy and Climate Change Secretary Ed Davey for a discussion about climate science and policy. Neil subsequently requested that people provide him with examples of the factual errors in this interview. Given that he began the show with several errors about the paper I co-authored finding a 97 percent consensus in the peer-reviewed literature that humans are causing global warming (the inspiration for the name of our blog), I would be happy to oblige.

Claims #1–4

"That [97% consensus] survey has of course been substantially discredited ... 35 percent of the abstracts were misclassified, and they were classified to the pro-global warming side. Professor Richard Tol ... has disassociated himself from that and said it's not reliable."

Verdict: False on all counts.

All of Neil's claims here refer to comments economist Richard Tol has made about our paper on his personal blog. He submitted those comments to the journal that published our paper, Environmental Research Letters, whose editor promptly rejected his submission. The editor noted that in addition to being "written in a rather opinionated style" and reading "more like a blog post than a scientific comment," most importantly,



"I do not see that the submission has identified any clear errors in the Cook et al. paper that would call its conclusions into question."

The claim that we "misclassified" 35 percent of abstracts is simply based on Tol's preference that our survey be less precise and make more sweeping generalizations. Our team read and categorized every abstract based on what they said about the causes of global warming, whereas Tol believes that every paper discussing the impacts of climate change should be placed in the 'no opinion' category. We classified these abstracts correctly based on the categories established in our study. Let's just take one quick example, from (Soulé 1992):

"Humans are engaged in an uncontrolled experiment in planetary heating. Each decade, the concentration of CO2, methane and other greenhouse gases in the atmosphere is increasing by about 4%. All signs point toward unprecedented rates of warming and climate change."

We categorized that as an explicit endorsement of human-caused global warming. Tol would call it "no opinion". You be the judge as to who's misclassified it.

Additionally, when we compared our abstract ratings to the authors' self-ratings based on their full papers, contrary to Neil's claim, we found that we had classified them more in the 'no opinion' category and less in the pro-human caused global warming categories than the authors themselves.

Histogram of Abstract Rating (expressed in percentages) minus Self-Rating. 1–3 = endorsed human-caused global warming, 4 = no expressed position, 5–7 = rejected human-caused global warming. Green bars are where self-ratings have a higher level of endorsement of human-caused global warming than the abstract rating. Red bars are where self-ratings have a lower level of endorsement of human-caused global warming than the abstract rating.

Regarding Neil's claim that Tol has disassociated himself from our study: Tol has never been associated with the analysis of our study. He was one of 29,083 authors of studies that we examined, and one of 1,200 authors who participated in the self-rating phase. So the statement that he has disassociated himself is meaningless. His opinions about how his own papers should be categorized are included in the 97 percent consensus in self-rated papers.

Those author self-ratings are a key component of our study and conclusions. In both the abstract ratings and author self-ratings, we found the same 97 percent consensus result. Tol has only criticized the abstract ratings survey; even if you disregard those results, the 97 percent self-ratings consensus remains.

This is why our results remain widely accepted. Neil's assertion that they have been "widely discredited" is simply a repetition of baseless claims made on climate contrarian blogs. If Neil relies on contrarian blogs for his climate information, that may explain why he is woefully misinformed on the subject.

Graph #1

In justifying only showing global surface temperatures from 1980 to the present day, Neil showed a faulty graphic of data from the UK Met Office and Hadley Centre (HadCRUT4). It appears to be a graph of the decadally smoothed HadCRUT4 data, but smoothed out even further to eliminate all the 'plateaus' before the year 2000.

Aside from the excessive smoothing, the graph is invalid after the year 2007. Using this decadal smoothing method, each temperature data point is the average of the surrounding decade. So for example, the temperature in 2012 is the average of the temperatures in 2007 through 2017. Problem: lacking a TARDIS, we don't yet know the temperature in 2017. The Met Office explains,

"Ideally the smoothing should stop before the filter 'runs off' the end of the series, but a series that has been shortened in this way appears not to be up-to-date ... Extending the data series can be done in a number of ways, but the method used for HadCRUT4 is simply to continue the series by repeating the final value."

To sum up, the graph presented by Neil is excessively smoothed, and half of the 'plateau' that was the main focus of the show is artificial.

Verdict: Neil's graph should be totally disregarded and thrown out. Here is an accurate representation of global surface temperatures, which shows that these sorts of 'plateaus' happen frequently.

Average of NASA GISS, NOAA NCDC, and HadCRUT4 monthly global surface temperature anomalies from January 1970 through November 2012 (green) with linear trends applied to the timeframes Jan '70 - Oct '77, Apr '77 - Dec '86, Sep '87 - Nov '96, Jun '97 - Dec '02, and Nov '02 - Nov '12.

Claim #5

When addressing his misleading 'plateau' graphic, Neil also claimed,

"The IPCC report says that the real CO2 emission rising temperatures really clicked in after 1980."

Verdict: False.

You can see from this figure in the 2001 IPCC report that human-caused global warming really kicked into gear around 1970, but rose steadily throughout the early- and mid-20th century.

Question #1

"Isn't that [global surface temperature] plateau a bit of a puzzle ... Is there at least the possibility - I put it no higher than that - that there is a disconnect now between CO2 emissions and temperatures?"

Answer: We don't yet know exactly how much each factor (e.g. low solar activity, more pollutants in the atmosphere, more ocean warming) has contributed to the slowed global surface warming, but we do know they have contributed to it. As Davey correctly noted, climate models predict that there will be decades with less surface warming and more ocean warming, which is exactly what we're currently seeing.

Davey also did a good job pointing out that Neil was focusing on air temperatures, but 90 percent of global warming goes into the oceans. When we account for all the heat the Earth is accumulating, it's warming at a rate equivalent to 4 Hiroshima atomic bomb detonations per second. There is no disconnect there - the planet is continuing to accumulate heat along with the rise in atmospheric carbon dioxide.

Source: Climate Nexus

Claim #6

"...the Arctic ice melt did not happen other than normally this year."

Verdict: Misleading

The veracity of this claim cannot be evaluated for two reasons. First, it's July. The annual Arctic sea ice melt season continues through September. There's still a good 2 months to go. Second, what exactly is "normal"? Since 1980, the Arctic has lost three quarters of its ice mass. This year's melt is consistent with that new normal of extreme summer sea ice melt, and so far it's even toward the lower end of the emaciated sea ice extent record over the past three decades.

Claim #7

"...the IPCC central forecast of almost 3 percent rise in temperatures. If it turned out, sometimes climate scientists are saying that it's actually going to be 1 percent..."

Verdict: False and confused.

It's difficult to figure out what Neil is referring to here, because he seems to have said "percent" where he meant "degrees Celsius". However, the IPCC projects a range of possible future global warming scenarios depending on the amount of greenhouse gases humans emit over the next century.

A 3°C average global surface warming above pre-industrial levels would be a fairly middle-of-the-road scenario. However, the planet has already warmed 0.8°C above pre-industrial levels, and we are committed to another half a degree Celsius just from the greenhouse gases we have already emitted. No serious climate scientist believes we can limit warming to 1°C by 2100 without radical greenhouse gas emissions reductions. On the contrary, Neil is suggesting we should do less to reduce emissions, which would commit us to the higher global warming scenarios. Davey again was right to say that we can only limit global surface warming to 2°C if we aggressively reduce greenhouse gas emissions.

The Final Verdict

Ed Davey deserves kudos for doing a very nice job explaining the science to Neil throughout the show. He also debunked Neil's exaggerations of the cost of reducing greenhouse gas emissions. On that point it's important to note that a valid economic analysis must consider both the costs and the benefits of a given policy. According to a recent study by Chris and Mat Hope, a ton of carbon dioxide emissions today costs us over $100. We reap economic benefits by reducing those emissions and avoiding the climate damages they cause.

As Davey noted, throughout the show Neil focused only on the bits of evidence that seemed to support his position. He focused exclusively on the slowed global surface warming while ignoring the warming oceans, melting ice, and rising sea levels. He focused on and exaggerated the costs of climate policy while ignoring their benefits. And he focused on attacks on our consensus paper by climate contrarian blogs while ignoring the fact that the 97 percent finding was the result of two independent methods, and also consistent with several previous similar surveys.

True skepticism requires considering all the available evidence, not just that which seems to support your desired conclusion.