More and more, reporters have been asking whether or not climate change could be responsible for this summer’s extreme weather. Thankfully, most have resisted the temptation to pin the events directly to global warming, placing them in proper climatic context instead.
For the last week, news outlets around the world have churned out stories about record-setting temperatures and blazing infernos around Moscow as well as flooding in Pakistan that the United Nations called the worst humanitarian crisis in recent history. To a lesser extent, there have also been plenty of reports about rain-induced landslides in China, severe droughts in sub-Saharan Africa, and the calving of an enormous iceberg from the Greenland ice sheet.
“The occurrence of all these events at almost the same time raises questions about their possible linkages to the predicted increase in intensity and frequency of extreme events” laid out in the Intergovernmental Panel on Climate Change’s (IPCC) 2007 assessment report, the World Meteorological Organization (WMO) reported Wednesday.
Indeed, before the WMO even made that observation, reporters were seeking out scientific sources that could provide answers. Articles and blog posts from Reuters, The Washington Post, Agence France-Presse, the Telegraph, BBC News, the Associated Press, New Scientist, and The Economist have all come to the same basic conclusion: While no single weather event can be attributed to climate change, more extreme weather events can be expected in a warmer world, and the ones we’ve seen this summer fit the IPCC’s predictions.
The contributions from New Scientist and The Economist are among the best of the bunch. Unlike some of the others, which explore the indeterminate climate connection but leave it that, they both explain (quoting from the latter) that “The immediate cause of the [the Russian heat wave and Pakistani flood, which appear to be linked] is the behavior of the jet stream, a band of high-level wind that travels east around the world and influences much of the weather below it.”
Basically, the jet stream’s current pattern has become “blocked,” as meteorologists put it, by north-south airflows high in the atmosphere. As a result, a high-pressure “ridge” has become locked in place over western Russia (with cooler than average temperatures to the east). The ridge intensifies the hot and dry conditions on the ground, which, in turn, intensify the ridge in a positive feedback loop. Meteorologists Jeff Masters and Rob Carver offered technical but useful explanations of the situation at Weather Underground, and an explanation of blocking is available at the National Weather Service’s Web site.
Peter Stott, the head of the climate monitoring and attribution at the U.K.’s Met Office, had an enlightening column in the Guardian explaining why the Russian heat wave and Pakistani floods might be linked, and delved into their connection to climate change. Wired Science’s Brandon Keim delivered a nice, clear explanation of the linkage between the weather events in Asia as well.
There were missteps, of course. The Telegraph mentioned the jet stream’s role in extreme weather, but its importance was obscured by the paper’s unfortunate decision to run the headline, “Climate change experts say global warming could be the cause.” Worse still was the BBC, which didn’t mention the jet stream at all (it only referred to “circulation anomalies”) and ran the headline, “Climate change ‘partly to blame’ for sweltering Moscow.” Such language—which suggests that we can, in fact, attribute specific weather events to global warming—should be strictly avoided.
Still, almost every outlet eschewed the temptation to say, “Look there! I give you global warming!” The New York Times’s Tom Zeller, Jr. saw that temptation coming at the end of July. In a smart piece for The Week in Review, he reminded readers that climate skeptics had seized on unusually cold weather last winter in order to mock climate science, and warned against resorting to such antics in support of it:
In any debate over climate change, conventional wisdom holds that there is no reflex more absurd than invoking the local weather.
And yet this year’s wild weather fluctuations seem to have motivated people on both sides of the issue to stick a finger in the air and declare the matter resolved — in their favor.
Last week, New York Times blogger Andrew Revkin provided a specific example of why scientists are reluctant to attribute single weather events to climate change. In a post about the calving of a massive iceberg from the Greenland’s Petermann Glacier on August 5, he quoted Andreas Muenchow, an oceanographer at the University of Delaware, who spotted the breakaway ice.