Over the weekend, two groups released so-called “game-changing” climate change studies.

The first, led by “converted skeptic” University of California-Berkeley professor Richard Muller, claims almost all of the warming observed in modern times is due to human activities. The second, led by blogger Anthony Watts, in an apparent attempt to diminish the impact of the Muller paper, argues warming in the U.S. since 1979 is about half the amount calculated by NOAA.

Both studies staged high-profile releases and represent concerted efforts to influence public perception about what we know about climate science. But neither has been published in a peer-reviewed publication and there is cause to question their legitimacy.

Muller summarized the results of his group’s study in an exclusive op-ed in the New York Times. Consider these key excerpts:

Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I’m now going a step further: Humans are almost entirely the cause.


How definite is the attribution to humans? The carbon dioxide curve gives a better match than anything else we’ve tried. Its magnitude is consistent with the calculated greenhouse effect — extra warming from trapped heat radiation. These facts don’t prove causality and they shouldn’t end skepticism, but they raise the bar: to be considered seriously, an alternative explanation must match the data at least as well as carbon dioxide does.


Science is that narrow realm of knowledge that, in principle, is universally accepted. I embarked on this analysis to answer questions that, to my mind, had not been answered. I hope that the Berkeley Earth analysis will help settle the scientific debate regarding global warming and its human causes.

Penn State climate scientist Michael Mann said Muller’s work essentially confirmed results from existing studies, adding little new to our state of knowledge. The Muller study results, Mann said (on his Facebook page): “...demonstrate what scientists have known with some degree of confidence for nearly two decades: that the globe is indeed warming, and that this warming can only be explained by human-caused increases in greenhouse gas concentrations.”

Similarly, Stanford climate scientist Ken Caldeira told Climate Progress: “I am glad that Muller et al have taken a look at the data and have come to essentially the same conclusion that nearly everyone else had come to more than a decade ago.”

Mann and Caldeira’s colleague, Ben Santer, a climate scientist at Lawrence Livermore National Laboratory, was less kind, arguing Muller’s tactic of releasing his study’s results before acceptance into a peer-reviewed journal could backfire. He told the LA Times:

“I think [Muller] can do great harm to the broader debate. Imagine this scenario: that he makes these great claims and the papers aren’t published? This (op-ed) is in the spirit of publicity, not the spirit of science.”

Regarding this claim that the release of results prior to official publication was an act of showmanship rather than science, Elizabeth Muller - co-founder and executive director of the Berkeley project and Richard Muller’s daughter - responded that the results were too important to withold and that the pre-release invites greater opportunity for constructive feedback from colleagues. She offered this defense to the LA Times:

I believe the findings in our papers are too important to wait for the year or longer that it could take to complete the journal review process. We believe in traditional peer review; we welcome feedback [from] the public and any scientists who are interested in taking the time to make thoughtful comments. Our papers have received scrutiny by dozens of top scientists, not just the two or three that typically are called upon by journalists.

But this defense rings hollow. The only difference between Muller’s results and the conclusions of the existing scientific assessment literature (such as the Intergovernmental Panel on Climate Change) is that Muller asserts “nearly all” of the recent warming is due to human activities over a longer timeframe whereas existing literature says “most” over a shorter timeframe. The claim that this single study was “too important” to hold back - especially in light of scores of other important studies which received no such pre-publication fanfare - reeks of arrogance on the part of the author team.

Just as the process for releasing the Muller et al. results was challenged, so too was the substance. Georgia Tech atmospheric science professor Judith Curry, who characterizes herself as a “lukewarmer”, (someone who believes humans are warming the climate but to an uncertain degree) was not at all swayed by Muller’s analysis. She wrote in her blog:

In my opinion, their analysis is way over simplistic and not at all convincing . There is broad agreement that greenhouse gas emissions have contributed to the warming in the latter half of the 20th century; the big question is how much of this warming can be attributed to greenhouse gas emissions. I dont think this question can be answered by the simple curve fitting used in this paper...

Irrespective of the flaws in Muller’s analysis or its merits - grabbing headlines in the New York Times prior to peer review represents an enormous tactical mistake. Peer review is the primary pillar of scientific legitimacy. Without it, a study has little to support it - which brings us to the Watts study.

Watts justified the release of his team’s new study prior to peer review - not coincidentally - using Muller’s rationale that pre-publication would attract more critical eyeballs to help bulletproof his work. But like Muller, Watts’ actions speak more to a publicity-motivated intent. On Friday, Watts halted all publication on his high-traffic blog Friday pending a “major announcement” Sunday afternoon presumably to build suspense ahead of the study’s release.

And no doubt the timing of the release of the Watts paper - the same day Muller’s New York Times op-ed ran- was purposeful to divert attention from Muller’s study. (Watts admits as much on his blog: “About a week ago I learned Muller was going to release and do the media blitz...Added anxiety”).

So what was the message of the Watts et al. study? Here’s what the press release says:

The new analysis demonstrates that reported 1979-2008 U.S. temperature trends are spuriously doubled, with 92% of that over-estimation resulting from erroneous NOAA adjustments...

In other words, Watts is asserting the U.S. temperature trends you’ve seen reported from NOAA about warming in the last few decades are inflated due to flawed adjustments made to temperature records. The unadjusted highest quality temperature records in the U.S., Watts claims, demonstrate about half the warming as NOAA’s adjusted data.

Roger Pielke, Sr., a Colorado State climate scientist who has expressed skepticism about NOAA’s temperature records, showered the Watts analysis with praise:

“This paper is a game changer, in my view, with respect to the use of the land surface temperature anomalies as part of the diagnosis of global warming,” he blogged.

If it seems surprising Pielke Sr. would offer such unqualified praise before this work had been peer reviewed, it turns out he was not an impartial player. Watts acknowledges Pielke Sr. for help “with edits and citations.”

Science blogger David Appell had it exactly right when he said the Watts paper is “exactly the kind of paper that most needs peer review: based on a lot of judgements and classifications and nitty gritty details....”

Furthermore, given the serious accusations Watts et al. make about the integrity of NOAA’s temperature analysis, it’s critical NOAA be given the opportunity to respond just as they did the last time Watts issued such a challenge in 2009. NOAA’s U.S. temperature record has been painstakingly constructed by many scientists over many years and many peer-reviewed publications support its methodologies.

The Muller and Watts studies no doubt represent a lot of hard work and may eventually prove to be valuable contributions to science. But we should reserve judgment on their significance.

And this new effort by these scientists to grab attention for studies that have not yet been vetted by other, independent scientists is disturbing and unproductive. It’s a disingenuous attempt to score points on a highly polarized scientific issue.

My advice? Ignore these publicity stunts and pay no attention to these studies until they have passed peer review. And even studies that have been peer reviewed should be viewed with a certain amount of skepticism until they have been confirmed in multiple subsequent studies and stood the test of time.

UPDATE, 10 p.m.: The New York Times Andrew Revkin has received an initial reaction from NOAA on Watts’ claims. See his blog post: A Closer Look at Climate Studies Promoted Before Publication. Also, my colleague Brad Plumer has an interesting take on the value of peer review. See his post: Two climate papers get hyped first, reviewed later. Isn’t that a bad idea?