Stories exploring a possible connection between climate change and extreme weather around the world continued over the weekend, with some scientists willing to venture personal opinions that recent events are likely (but not demonstrably) the consequence global warming.
Last week, reporters produced commendably temperate coverage of this summer’s abnormal weather. In general, reporters explained that while scientists cannot attribute individual droughts and storms to global warming, they expect their intensity and frequency will rise with temperature. Stories over the weekend went a step farther, however, emphasizing that a number of scientists think that the recent parade of unusual phenomena is evidence that extreme weather is already becoming more frequent and intense.
On Saturday, The New York Times juxtaposed photos of monsoonal floods in Pakistan, heat-wave induced wildfires in Russia, and torrential downpours in Chicago, over a front-page story headlined, “In Weather Chaos, a Case for Global Warming.” Asking whether or not climate change is, at present, causing more weather extremes, the article found that, “The collective answer of the scientific community can be boiled down to a single word: probably.”
Generally, I’m leery of “collective” answers, especially those that are “boiled down,” but the article is actually very nuanced. First of all, it does not report that this summer’s extreme events are directly attributable to global warming, only that there is a chance that they are, since warming appears to be increasing the instance of extreme events generally. Second, most of the story is dedicated to explaining why a scientific answer to weather-climate connection is not, in fact, easily reduced to a one-word reply:
Theory suggests that a world warming up because of those gases will feature heavier rainstorms in summer, bigger snowstorms in winter, more intense droughts in at least some places and more record-breaking heat waves. Scientists and government reports say the statistical evidence shows that much of this is starting to happen.
But the averages do not necessarily make it easier to link specific weather events, like a given flood or hurricane or heat wave, to climate change. Most climate scientists are reluctant to go that far, noting that weather was characterized by remarkable variability long before humans began burning fossil fuels and releasing greenhouse gases into the atmosphere.
Nonetheless, a few scientists have overcome some of that reluctance in the last few days, expressing their belief that, while conclusive evidence is lacking, they strongly suspect that global warming had a role to play in this summer’s extreme weather.
“If you ask me as a person, do I think the Russian heat wave has to do with climate change, the answer is yes,” NASA climate modeler Gavin Schmidt told the Times. “If you ask me as a scientist whether I have proved it, the answer is no — at least not yet.”
Schmidt was more restrained during an interesting CNN interview with Fareed Zakaria, which also included Jeff Sachs of Columbia University’s Earth Institute and Pat Michaels, a climatologist who has adamantly opposed climate-warming reducing greenhouse gas emissions. But he’s not the only scientist ready to make an informed guess. In a column for the Guardian, Potsdam University climatologist Stefan Rahmstorf (who, with Schmidt, writes for the blog RealClimate.org) wrote:
Looking only at individual extreme events will not reveal their cause, just like watching a few scenes from a movie does not reveal the plot. But, viewed in a broader context, and using the logic of physics, important parts of the plot can be understood…
This cluster of record-breaking events could be merely an streak of bad luck. But that is extremely unlikely. This is far more likely to be the result of a warming climate – a consequence of this decade being, worldwide, the hottest for a thousand years.
Rahmstorf catalogues a host of extreme events in recent years, and offers a good explanation of why greenhouse gases are clearly what’s throwing the Earth’s energy budget out of whack (see also Andrew Freedman’s interesting conversations with Peter Stott, head of the U.K. Met Office, and Stu Ostro, senior meteorologist for The Weather Channel, at Climate Central and The Washington Post, respectively). As for the proof that Schmidt mentioned, the Times’s article went on to point out that:
In the United States these days, about two record highs are being set for every record low, telltale evidence that amid all the random variation of weather, the trend is toward a warmer climate.