Politifact tells us about American politics and science. We should listen.

orwellSummary: This vignette illustrates important aspects of the climate change debate, and why it has failed to gain sufficient support from Americans to pass large-scale public policy measures. For two decades journalists and scientists have cooperated to produce political propaganda, exaggerating and misrepresenting the work of the IPCC. Their failure should inspire us, showing a resistance to manipulation greater than many people expected (it surprises me).

My post, which started this kerfuffle

In July I published The 97% consensus of climate scientists is only 47%, which showed the hidden results of an excellent survey of scientists’ agreement with the IPPC’s attribution statements about the role of anthropogenic greenhouse gases in global warming. It was high, but lower than usually described — and below the standard for significance. The question has important implications; Obama’s sweeping Clean Power Plan rests on this finding (details here).

it attracted some attention on skeptics’ websites, and pushback from climate activists (both laypeople and scientists). Then GOP presidential candidate Rich Santorum cited this information, and the activists began their usual smear campaign. The facts are quite simple, for those who want to know.

The article at Politifact

Politifact started the cover-up with “Santorum cites flawed climate change figure, and misquotes it” by Linda Qui. She asked me for information. I gave her several thousand words (which I’ll publish tomorrow). She didn’t find anything useful for smearing me, so she ignored it.

Below are the relevant parts of her hit job. My responses follow each quote. Qui tells me she consulted Verheggen and “6 other climate scientists/people who study the consensus issue” “and they all agreed with the survey author”. As you will see below, all that work produced only the weakest of rebuttals. But we can learn much from their attempt.

(a)  Politifact’s big conclusion!

The real finding of the survey actually backs the idea of scientific consensus on climate change, despite varying levels of confidence, said Verheggen.

“It is clear from our survey that a strong majority of scientists agree that greenhouse gases originating from human activity are the dominant cause of recent warming,” he said. That’s consistent with most of the literature on scientific opinion about climate change, experts agreed.

“You don’t get anywhere near 57% when surveying the broad earth science community, and you get very close to full consensus when you ask the experts in climate science,” said Peter Doran, a professor of earth science at Louisiana State University.

National Science Board member James Powell surveyed what’s actually published in scientific journals, finding that the consensus in the literature is about 99.9%. And multiple independent studies have “asked scientists directly” and found consensus levels of around 97%, said William Anderegg, who studies climate change at Princeton University.  “Those studies were rigorously peer-reviewed and thus should be considered more credible than a blog post that misreads an institute report,” he said.

The four surveys Politifact mention asked in general terms about scientists’ agreement that there has been anthropogenic human warming.


  • Quantifying the consensus on anthropogenic global warming in the scientific literature” by John Cook et al (Environmental Research Letters, 22 April 2013) looked for studies that “implied that humans were causing global warming”.
  • Powell’s paper used Cook’s data to find studies rejecting “anthropogenic global warming.”
  • Stacy Rosenberg et al (Climate Change, August 2010; ungated copy here) asked scientists if they “can say with great certainty that global warming is a process that is already underway” and that “with great certainty that human activities are accelerating global warming.”
  • Examining the Scientific Consensus on Climate Change” by Dorlan and Zimmerman (EOS, 20 January 2009) asked similar questions: “When compared with pre-1800s levels, do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?” and “Do you think human activity is a significant contributing factor in changing mean global temperatures?”


These studies (and 5 others described here) find high levels of agreement with those broad statements. But such statements — Gallup-like polls — don’t provide a basis to restructure the world economy. Science is about precision, as found in the IPCC’s attribution statements, which is why they are so valuable. Here’s the key finding in AR5 about greenhouse gases (repeating more precisely the same finding in 2007’s AR4). Compare it with the above questions.

“more than half of the observed increase in GMST {global mean surface temperature} from 1951 to 2010 is … due to the observed anthropogenic increase in GHG {greenhouse gas} concentrations.”

The PBL survey tested agreement with this attribution statement, asking for their “confidence level” about it — more useful than asking about belief in anthropogenic global warming as a true/false proposition. Of course a precise (i.e., narrower) statement like the IPCC’s will get lower levels of agreement than the broad statements tested in previous surveys.

How many scientists agreed at the “extremely likely” level (which the IPCC defines as 95%+ level, the usual minimum standard for use in science and public policy)?  43% of all 1,868 respondents (47% excluding the “don’t know” group).

How many agreed at the “very likely ” level (90%+ in the IPCC’s reports), which is what AR4 and AR5 assigned? 57% (again, less excluding the “don’t knows”). A majority, although a small one.

These findings are surprisingly low, and so unmentioned by the authors of the PBL study. The reaction to my post shows the strong effort to hide them.

These findings of the PBL report are consistent with the previous studies (agreeing with anthropogenic warming), but provide more detail. By describing them as contradictory Politifact misleads its readers. Verheggen, Doran, Powell, and Anderegg participate in the deception (perhaps ignorantly, as they might not have read my post — but just joined in the smear like good boys).

Politifact’s big conclusion is a magician’s trick, moving the pea while the audience watches from 95% agreement that more than half of warming since 1950 is anthropogenic to the far broader agrees with anthropogenic warming.

That’s how the global warming crusade runs. Deception and misrepresentations are activists’ standard tactics. the campaign’s big lie: if you disagree with predictions of catastrophic anthropogenic global warming, then you deny global warming. By repetition they’ve embedded this “logic” in the minds of millions. They even indoctrinated children, such as this student at U NH, who responds to Cruz’s correct statement that the 2 NASA-funded satellite datasets show a pause in warming since ~2000 by saying “Ted Cruz insults University of New Hampshire, denies the earth is warming“.

Read rest…