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More on Extreme Weather

Day Two stories go a step farther in drawing connection to climate change
August 17, 2010

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.

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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 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.

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.

I would agree that this story merits more in-depth reporting, and the media have a duty to connect the dots between extreme weather and climate change. Those connections are not “unambiguous,” however. Stott, the head of the U.K.’s Met Office, had a great column in the Guardian last week, explaining that while he and colleagues were able to demonstrate that the European heat wave of 2003 would have been likely without global warming:

For some other types of extreme weather there is a need for more research. For example, circulation changes could mean that some extreme weather events become less, not more likely under climate change. Better understanding of which extreme weather events are part of normal variations rather than of a developing pattern of climate change effects will help societies adapt to the challenges of ongoing climate change. Next week in Colorado, experts from the UK and US forecasting centres at the Met Office and NOAA will meet to consider how we can provide better information on the causes of extreme weather in near-real time.

Until more research is hand reporting that the weather-climate connection is “unambiguous” will only sow confusion. Moreover, journalists don’t need to overreach in order to be agenda setters. The Times’s front-page article was a great example of how reporters can highlight scientists’ growing suspicion that global warming is steadily raising the baseline for wild temperature swings while also being honest about the limitations of their current knowledge.

Other papers are making similar efforts, pointing out weather-climate connections without overplaying them. Take the very laudable opinion column by the editor of the Albany Times Union, Rex Smith, apparently penned in response to readers’ complaints about a front-page Associated Press article the paper ran last week, explaining that this summer’s extreme weather jibes with climatologists predictions about a warmer world. In it, Smith writes:

Let’s be clear, as the Associated Press article we published was: You can’t blame climate change for any single weather event — not for last year’s wet summer here, for example, nor for the disasters that have befallen various corners of the world this summer. But scientists say that a warmer world is one where extreme weather events are more likely to occur, and that’s what we’re seeing nowadays…

The topic is worthy of greater exposition than I can offer here, but in terms of our reporting, the principle at stake is simple: Even if what we need to know isn’t what we want to hear, it’s quite simply what we are owed by anyone who professes to practice good journalism.

Thankfully, many editors appear to be of the same mind as Smith—ready to let their reporters delve into a complex subject that defies easy answers in order to deliver nuanced stories that stress scientists’ concerns about extreme weather and place them in proper climatic context.

Curtis Brainard writes on science and environment reporting. Follow him on Twitter @cbrainard.