News•October 8, 2014

2014 Extreme Weather: Looking for Climate Ties

The ongoing, intense drought in California; the nonstop storms that left parts of Great Britain waterlogged all winter; the bitter winter cold in the eastern U.S. — these are just some of the extreme weather events from this year that could be examined in an annual report that looks for the fingerprints of climate change in such occurrences.

Shasta Lake, the largest manmade lake in California, was at 36 percent of capacity when this photo was taken in January 2014. As of Sept. 28, it was at 26 percent of capacity.
Credit: USGS/Angela Smith

The report, a supplement published in the journal Bulletin of the American Meteorological Society since 2011, rounds up some of the most notable events from the previous year and tries to answer the question increasingly being asked: Did climate change cause this? Not only that, but it attempts to do so relatively quickly, (in the world of science, anyway) after the event, with the studies coming out in early October of the following year.

Extreme event attribution, as the nascent field is called, is a quickly growing one, with more and more researchers publishing studies that aim to tease apart the influences of climate change and natural variability on some of the biggest weather outliers we experience — and do so on shorter timescales.

“People are really engaged when events are happening and we’re trying to speak to that by saying something that’s relatively robust” and fairly close to the event, said Peter Stott, a climatologist with the U.K. Met Office Hadley Centre and one of the report’s editors. The effort isn’t without critics, though, who say such efforts can confuse the conversation about what we know about the effects of global warming.

Not Random

The 2013 BAMS supplement that was released Sept. 29 had 22 studies done by 20 research groups who looked at 16 extreme events, up from just 6 studies on 6 separate events in the first issue released in 2011. The events examined in the volume are picked by the particular groups researching them and are generally events that happened where those groups live.

“This is not a random selection of events around the world,” said another of the report’s editors, Thomas Peterson, of the U.S. National Climatic Data Center. “People are often working on areas of interest to them personally and that impacted them.”

That limitation means that the supplement isn’t necessarily a comprehensive look at all the extreme weather from the previous year. The most recent review, for example, left out a significant event, Typhoon Haiyan. At the time that the intense storm hit the Philippines, the contributions of sea level rise to its storm surge and the potential effect of warming on the storm’s strength were hot topics. But though the BAMS editors tried to find a research team that could look into the storm, none could do it on the short timescale required by the review.

The editors of the supplement say that for future editions they hope to encourage more studies of events in places that are currently comparatively neglected, like South America and Africa.

“We would like this to be more geographically diverse,” Peterson told Climate Central.

Looking Ahead

What events from 2014 that the research groups focus on is still very much up in the air, as the editors don’t expect to have authors and their topics lined up until the end of the year and their papers in hand until the beginning of April 2015.

Lead editor of the 2013 supplement, Stephanie Herring, also of the NCDC, said that of the events that have happened so far in 2014, she’d like to see more studies of the devastating California drought (which was addressed in this year’s issue), as well as the associated wildfires, a topic that so far hasn’t appeared in the BAMS review.

She also mentioned the relatively cold winter in the eastern U.S., which in some places forced schools to shut down on particularly frigid days. The winter was actually closer to an average one, but seemed bitter compared to recent mild winters.

“I think it’s an interesting example of how we perceive extremes,” Herring told Climate Central. “I would love to see an author group to take that on.”

The amount of rain that fell across the United Kingdom during winter 2013-2014 as a percent of average.
Credit: U.K. Met Office/Crown copyright

Stott, citing an event from his own backyard, said that he would like to see someone tackle the series of storms that dropped record amounts of rain on parts of England and Wales — what Stott described, in true British understatement, as “a very wet winter.”

Young Field

Some climate scientists, including Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colo., and Michael Mann of Penn State University, have leveled criticism at some of the studies included in the BAMS report and at the field of extreme event attribution in general, saying it can confuse the public conversation on climate change’s effects and that many of the studies aren’t asking the right questions.

For example, Trenberth and Mann questioned the methods used in two of the three studies that looked at the California drought in this year’s review, saying that they didn’t account for key factors that likely played a role. Those studies reported no link to climate change, which doesn’t mean there isn’t one, just that those studies didn’t find it (the third study did find a connection). But some media reports said that the drought had no connection to climate change, which Mann said confuses the public discussion around such events.

Mann says that he appreciates the efforts of attribution work and reviews like the BAMS one, but that such ad-hoc efforts lack the rigor and structure of larger efforts like the Intergovernmental Panel on Climate Change assessments that reflect the general consensus in the climate community.

“For these reasons I am unconvinced that these special reports properly inform the larger public discourse over the climate change/extreme weather discussion,” Mann wrote in an email. “I fear that they create more confusion than clarity.”

The scientists behind the attribution work acknowledge that there is a lot to learn about doing attribution science and about communicating their findings to the public, but “the fact that we’re not doing it perfectly now, doesn’t mean that we should stop doing it,” Stott said.

He and other authors and editors said that this early work will help scientists learn what methods do and don’t work to answer questions of attribution and help to show the strengths and weaknesses of climate models in projecting future extremes.

“The value of this is going to come through in future years,” Stott said.

Another climate scientist who sits outside the attribution community agreed with Stott. Ted Shepherd, at the University of Reading in England, said that while he has qualms about some of the studies, says that he supports efforts like the BAMS review, as larger efforts like the IPCC are often cumbersome and less nimble when addressing recent events.

As the field of attribution grows, it’s sure to evolve, as will the BAMS report, the editors said.

“Three years in [to the BAMS effort], I think we’re still learning,” Herring said, adding that the field in general is a very young one.

“This field is barely a decade old,” she said. “It’s certainly grown very quickly in that decade . . . but it is still quite new.”