Climate skeptics perform independent analysis, finally convinced Earth is getting warmer
By John Timmer | Published about 2 hours ago
Last week, a project called Berkeley Earth released drafts of its findings. The project was started by a physicist, Richard Muller, who had previously expressed doubts about the mathematical rigor of climate science; it received funding from a variety of sources, including the Department of Energy and foundations set up by Bill Gates and the Koch brothers. The Berkeley Earth team set out to analyze records of the Earth's surface temperatures to answer questions about the trajectory of the planet's recent warming that had been raised by skeptics and contrarians. To a very large degree, it discovered that climatologists had been doing a pretty good job after all.
Climatologists have generated a number of reconstructions of global temperature trends based on instruments that have been recording temperatures since the 1800s. However, one of those records was produced by members of the Climatic Research Unit at the University of East Anglia. That record became embroiled in controversy: the CRU was the target of e-mail thefts, was unable to release some of its records due to commercial agreements, and had destroyed some paper copies of original data decades earlier. NASA and NOAA, however, performed independent reconstructions based on publicly available data.
Even those, however, had become the targets of criticism. Recording stations were moved, their surroundings urbanized, and researchers performed adjustments or dropped some stations entirely in order to compensate. Various parties hostile to the findings of climate science have raised questions about this process. Have the scientists really compensated for urbanization? Was the trajectory of the modern warming really as extreme as the temperature records were showing?
And those were the moderate voices. At the more extreme end of the spectrum, some accused researchers of selectively dropping only stations that showed cooling trends, and raised questions about whether the planet had warmed at all. These questions weren't very realistic—melting ice, migrating species, and other factors made it pretty clear the planet was warming—but the climate debate has no shortage of unreasonable voices.
Rerunning the numbers
In any case, the Berkeley Earth project set out to answer all of those questions. It would use many more stations, perform an independent reconstruction of global temperatures, and examine the effect of urbanization. And it has now completed that analysis and posted drafts of the four papers it has submitted to peer reviewed journals (they're currently in the review process).
It's not clear that they will all be published, because a few of them largely duplicate information that's already out there, as even the project head admits. "Our biggest surprise was that the new results agreed so closely with the warming values published previously by other teams in the US and the UK," said Richard Muller. "This confirms that these studies were done carefully and the potential biases identified by climate change skeptics did not seriously affect their conclusions."
So, with a different set of temperature stations, Berkeley Earth has succeeded in producing a graph that looks nearly indistinguishable from those of the other research groups. Is it possible to produce a biased record? Absolutely—about a third of the stations in Berkeley Earth's dataset show a cooling trend over the past 70 years. But, given this analysis, there's no reason to take give any credibility to accusations that climate scientists were cooking the books on temperatures.
But could the climate record be inadvertently biased? Critics have suggested that urbanization and the changing environment around many temperature stations have created a false warming signal; this is the premise behind the Surface Stations project, which went out and rated US instruments for likely problems. Both of these issues had been tackled by the scientific community. A paper from NOAA scientists looked at the best-rated US surface stations, and found they produced a temperature plot indistinguishable from that of the network as a whole. Berkeley Earth essentially duplicates this analysis.
Similarly, a group of NASA scientists (including James Hansen—yes, he still does science) used satellite images of nighttime lighting to determine which temperature stations are in urban areas, and found that these have a minimal impact on the temperature record. Berkeley Earth used a different source of urbanization information (daylight imagery that was processed by a machine learning algorithm), but come to the same conclusion: the urban heat island effect isn't skewing the temperature record.
Is there anything new here at all? The primary new contribution seems to be in a paper that focuses on short term variability in the climate. The Berkeley Earth record shows a good correlation between surface temperatures and variability in the North Atlantic. The El Niño-Southern Oscillation, which takes place in the Pacific, is generally regarded as the main driver of short-term variability, so this goes a bit against the grain. It's possible that this is a result of Berkeley Earth's focus on land-based readings, but we'll have to await their next analysis, which will include ocean readings, to see.
A sanity check for skepticism?
With the papers released, however, a publicity war has broken out. Richard Muller, one of the leaders of Berkeley Earth, penned an editorial in which he ignores the previous work by NASA, NOAA, and others, and claims there was good reason to be skeptical of the temperature record. Until now, that is. Berkeley Earth has largely recapitulated that previous work, so now it can all be trusted, and climate skeptics should simply move on to something else. Muller may have been one of the only people to have actually done what anyone skeptical of the climate scientists should do—perform an independent check of their work—but his public spin on his results is completely unrealistic.
Of course, like the NOAA study before it, Berkeley Earth undercuts the whole rationale behind the Surface Station project, and the people behind that are not happy. After posting nearly any trivia that came along on their blog (called Watts Up With That, after its lead, Anthony Watts), they have suddenly gotten very upset that the four papers were released before going through peer review—at which point they think they should be rejected for publication.
Stranger still, Watts and a number of others are now disowning their past, claiming to never have doubted that the Earth had been warming, and complaining that Muller's editorial caricatures their view up as a straw man. That's hard to reconcile with Watts' past statements. In a document he prepared for a think tank, Watts had written, "Instrumental temperature data for the pre-satellite era (1850-1980) have been so widely, systematically, and unidirectionally tampered with that it cannot be credibly asserted there has been any significant 'global warming' in the 20th century." Now, after Berkeley Earth's release, he claims to have never questioned that the Earth had warmed. Other prominent skeptics are saying similar things.
But Watts still doesn't trust Berkeley Earth's results. And, based on the comments on his blog, most of his readers don't either. That suggests that, contrary to Muller's expectations, this won't be the end of the skepticism of the temperature record.
What it may help do is drive those who keep questioning whether the Earth has warmed further to the fringes, where they can join those who question whether the greenhouse effect exists even after a century of work has confirmed that it does. That's a territory that doesn't merit the label skepticism anymore.
Actual skeptics might see this as an opportunity to focus on the scientific community's attribution of the temperature changes Berkeley Earth has confirmed, which is primarily ascribed to anthropogenic influences. There's an entire chapter of the IPCC report devoted to attribution, though, so any scientific skepticism should at least start by addressing the arguments outlined there.
Photograph by BBQ Junkie