Climate-change skeptics dispute such statistical arguments, contending that climatologists do not know enough about long-range patterns to draw definitive links between global warming and weather extremes. They cite events like the heat and drought of the 1930s as evidence that extreme weather is nothing new. Those were indeed dire heat waves, contributing to the Dust Bowl, which dislocated millions of Americans and changed the population structure of the United States.
But most researchers trained in climate analysis, while acknowledging that weather data in parts of the world are not as good as they would like, offer evidence to show that weather extremes are getting worse.
Unfortunately, the article doesn’t present much more of that evidence. It mentions a government report (pdf) from 2008, which identified changing weather patterns across U.S., but could have gone farther. The Intergovernmental Panel on Climate Change’s 2007 report, for instance, contains a useful FAQ section (pdf), which lays out recorded observations of decreases in cold nights, increases in warm nights, increases in heavy precipitation events, and increases in droughts in various parts of the world. [Update, 4 p.m.: Justin Gillis, the author of the Times article, followed up with a good blog post offering more supporting evidence a warming-related rise in extreme weather.]
It is also unfortunate that the Times never specifies the basis for its statements about the opinions of “most researchers” and their “collective answer” to the climate-weather question. I don’t doubt the statements’ accuracy, but words like “consensus” have been become so controversial in today’s media that the justification for such quantifications bears mentioning. In the case of the Times’s article, is the “collective answer” of “most researchers” represented by the IPCC’s report? By the large number of scientists that its reporters interviewed? What? The reader needs to know, because confusing statements about consensus are rife.
Take, for example, this headline at The Wonk Room: “Climate Experts Agree: Global Warming Caused Russian Heat Wave.” That bold proclamation is based on statements from two people, in particular. The first is Michael Tobis, a research scientist associate at the University of Texas, who wrote on his blog:
… right now I feel like hazarding a guess. As far as I understand, nothing like this has happened before in Moscow … it may turn out reasonable, in the end, to say “the Russian heat wave of 2010 is the first disaster unequivocally attributable to anthropogenic climate change”. (I also ventured something like this about the Australian fires last year.)
The second is Rob Carver, a meteorologist at Weather Underground, who has provided some of the best descriptions of the “blocking” of the jet stream that is the proximate cause of the heat wave in Russia. In an e-mail exchange with The Wonk Room, Carver wrote:
I agree with Michael Tobis’s take at Only In It For the Gold that something systematic has changed to alter the global circulation and you’ll need a coupled atmosphere/ocean global model to understand what’s going on. My hunch is that a warming Arctic combined with sea-surface-temperature teleconnections altered the global circulation such that a blocking ridge formed over western Russia leading to the unprecedented drought/heat wave conditions. Without contributions from anthropogenic climate change, I don’t think this event would have reached such extremes or even happened at all. (You may quote me on that.)
Like Schmidt in the Times, both Tobis and Carver are inching out onto a limb here, which is fine (the limb seems to grow sturdier by the day), but The Wonk Room’s decision to use a “guess” and “hunch” to declare that “climate experts agree [that] global warming caused the Russian heat wave” is grossly misleading. Likewise, I recently received a memorandum from Friend of the Earth, an environmental group, addressed to “journalists covering extreme and unusual weather events.” It argued that:
Some media outlets have now begun to examine the connections between the extreme weather and climate change, but this story merits more coverage and in-depth reporting. The connections between a warming climate and extreme weather are unambiguous, and the media has a duty to connect the dots.