The researchers behind the curious Berkeley Earth Surface Temperature study have released their latest results, concluding that the globe has warmed around 2.5 degrees Celsius over the past 250 years (see graph at right; PDF available here). Discussing the unpublished work with typical flair in an op-ed for the New York Times, physicist and self-proclaimed skeptic-turned-believer Richard Muller said “essentially all” of the increase is due to humans.
Incorporating more data into a single record that extends nearly a century beyond other versions, the study aligns with prior analyses but comes down even stronger than the Intergovernmental Panel on Climate Change by negating the impact of solar variability, Muller says. What’s left is a strong correlation between carbon dioxide and temperature. “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,” wrote Muller, a professor at the University of California, Berkeley.
The basic notion that greenhouse gases causes global warming is hardly newsworthy, and the study has been by and large treated as such within the climate community. But some are once again questioning the way Muller and his team have gone about their work as well as the conclusions they are drawing. University of Georgia climatologist Judith Curry, who was a co-author on the prior studies but declined to sign her name to the latest, offered a lengthy criticism on her blog (which also features an independent analysis of the BEST paper). Although the temperature record itself is useful, she asks this question: If determining attribution is as simple as comparing a couple of curves, why is everybody else wasting their time with sophisticated modelling and analyses?
This is not the first time Muller has released preliminary results from the so-called BEST study. Back in October, the group made initial waves with early results suggesting roughly 0.9 degrees Celsius of warming since the 1950s (see “Different method, same result: global warming is real“). Although Muller said the papers were submitted for peer review at the time, none of them have been published as of yet. Many scientists have questioned his tendency to seek publicity before going through the peer-review process, including Lawrence Livermore National Laboratory climatologist Benjamin Santer, quoted today in the Los Angeles Times:
“I think you 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.”
And as it happens, there are already questions floating around about exactly this possibility.
Canadian economist Ross McKitrick, whose earlier work with fellow Canadian Steve McIntyre raised questions about mainstream climate reconstructions, just posted a statement saying he was a reviewer on one of the papers (Influence of Urban Heating on the Global Temperature Land Average) at the Journal of Geophysical Research. What’s more, McKitrick suggests that the journal actually “turned the paper down and asked for major revisions” before Muller and his team made their initial announcement last October. McKitrick says he recommended against publishing a second version of he paper in March, and then went on to post both of his reviews.
“I take the journal peer review process seriously and I dislike being placed in the position of having to break a commitment I made to JGR,” McKitrick writes, “but the “BEST” team’s decision to launch another publicity blitz effectively nullifies any right they might have had to confidentiality in this matter.”
Elizabeth Muller, Richard Muller’s daughter and executive director of the BEST study, reported earlier on the Andrew Revkin’s New York Times blog Dot Earth that the team is working through the review process:
“All of the articles have been submitted to journals, and we have received substantial journal peer reviews. None of the reviews have indicated any mistakes in the papers; they have instead been primarily suggestions for additions, further citations of the literature. One review had no complaints about the content of the paper, but suggested delaying the publication until the long background paper, describing our methods in detail, was actually published.”
Responding to an inquiry from Nature, Elizabeth Muller confirmed that McKitrick reviewed the urban heat island paper and that the paper was technically rejected the first time around. “McKitrick did indeed suggest useful changes to the paper, many of which we made, but our basic results do not depend on these issues,” she wrote. “JGR has a method of technically rejecting a journal while encouraging the authors to revise the paper and re-submit. Apparently they do this to give the authors more time to make changes (otherwise, authors have only about a month to make revisions).” Muller declined to release information about the timing of the peer review process.
It’s hard to know what to make of all this. In the end we’ll have to wait for the peer review process to run its course. But climate skeptics have already seized on the news, and it is unlikely they will let go.
As it happens, one group of prominent skeptics has released a study claiming problems with the US temperature record (part of the same record analyzed by BEST) that lead to an overestimation of warming from 1979 to 2008. The study has yet to be published, but on the blog Watts Up With That Anthony Watts and fellow authors write that the announcement of the paper prior to publication “follows the practice embraced by Dr. Richard Muller.”
Graphic source: Berkeley Earth Surface Temperature study