Climate change found to have spurred worldwide heatwaves

But floods and droughts have less certain links to planetary warming.

 

The weather has been crazy lately. California, described recently in the New Yorker as the nation's "fruit basket, salad bowl and dairy case," is starting to look more like its day-old bread shelf, growing staler with each day that passes without rain. Communities in Colorado had the opposite problem around this time last year, with the rain coming on too strong for too long, flooding roads, homes and parks. Not long after that, South Dakota enjoyed a stretch of unusually balmy 80-degree days only to be whiplashed by 70-mile-per-hour winds and snow that buried or simply chilled to death thousands of cattle. 

There is an inevitable question that now comes with each wild weather event like these: What's climate change got to do with it? It's a really tough question to address in the immediate aftermath, when people most crave answers. But thanks to rapid advances in a field known as "attribution science," researchers, given a little time, are starting to be able to say "a little," "a lot," "not much" or "we're still not sure."

Colorado floods
Flooding in Boulder County, Colorado in 2013. Photo courtesy of Colorado National Guard.

A collection of studies published last week in the Bulletin of the American Meteorological Society did just that for the California drought, and last year's floods and blizzard in Colorado and South Dakota, as well as other wacky weather events around the globe, like the 2013 Australian heat wave.

The results were mixed. The most conclusive came from five studies that used different methods to tease apart the role of manmade climate change in the sweltering spells that Australians sweated out last year. Climate scientist David Karoly told the New York Times that 2013's hot temperatures in Australia were "virtually impossible without climate change." If those sound like strong words, it's because they are, wrote reporter Justin Gillis: "It is perhaps the most definitive statement climate scientists have made tying a specific weather event to global warming."

Climate change was also found to have played a role in the other heat waves studied, though not quite as large a role as it appears to have played in Australia. The Colorado floods and South Dakota blizzard, on the other hand, were not found to have been made more likely by climate change, nor could its fingerprint be conclusively seen in the California drought. Researchers said that the role climate change plays in extreme precipitation events and drought is in need of further study. 

What to make of all this? Perhaps the most important takeaway is that climate change is no longer a future threat. It's here and affecting the weather we experience today.

Another is that climate models — which are used both to project future conditions, and to parse out the roles of manmade warming and natural variability in current weather events — are at this point much better at dealing with temperature than precipitation or drought. In part, says Stephanie Herring, the lead editor of the recent studies, that's because the observational and paleo record is really robust for temperature. We have a really good sense of how hot and cold it's been thousands of years in the past, which makes it easier to judge whether temperature swings now are, in fact, "extreme." 

Plus, precipitation and drought are much more complicated processes to model. "The dynamics and physics of rainfall are much harder to capture," says Herring, who works out of Boulder, Colorado. "We had really bad flooding in Boulder last year, but I live in a town where our river never crested. Jamestown, 15 minutes from here, was destroyed."

Drought, she adds, is the result of a combination of a whole bunch of environmental conditions and atmospheric processes. In the recent studies, for instance, scientists ran models incorporating different sea surface temperatures to see if a warming ocean raised the likelihood of the drought. They found it didn't. Another group looked at the influence of climate change on something they call the "ridiculously resilient ridge," a high-pressure pattern in the North Pacific that has been stubbornly hanging out and blocking storms from reaching California. They found climate change had increased the chance of such a ridge forming. But the question of how exactly the pattern influenced the amount of precipitation California has or hasn't received wasn't addressed in the paper, says Herring, making it tough to offer a definitive statement about climate change's role in the Golden State's withering.

So why bother spending time picking apart the recent past? "By understanding what's causing extreme events today, it can help us understand what might cause extreme events tomorrow," Herring says. "Climate change is not necessarily driving these things one way or another. That impacts the way communities might prepare for future events." 

Cally Carswell is an HCN contributing editor based in Santa Fe, New Mexico. 

High Country News Classifieds
  • LAND AND WATER CONSERVATION DIRECTOR
    The Land and Water Conservation Director is a full-time salaried position with the Mountain Area Land Trust in Evergreen, CO. The successful candidate will have...
  • ARIZONA PROGRAM MANAGER
    National Parks Conservation Association (NPCA), the nation's oldest and largest national parks nonprofit advocacy organization seeks an Arizona Program Manager. The Arizona Program Manager works...
  • CROWN OF THE CONTINENT COMMUNITY CONSERVATION SPECIALIST
    THE WILDERNESS SOCIETY is seeking a Community Conservation Specialist, for the Crown of the Continent DEPARTMENT: Conservation CLASSIFICATION: Grade 6 Specialist/Representative (Low of $54K) REPORTS...
  • ASSISTANT FARM DIRECTOR
    About The Organization Building community through fresh vegetables is at the heart of the Sisters-based non-profit, Seed to Table Oregon. Based on a four-acre diversified...
  • CARPENTER WANTED
    CARPENTER WANTED. Come to Ketchikan and check out the Rainforest on the coast, Hike the shorelines, hug the big trees, watch deer in the muskeg...
  • DYNAMIC EXECUTIVE DIRECTOR
    VARD is seeking an Executive Director to lead a small legal & planning staff dedicated to the health and sustainability of Teton Valley Idaho and...
  • WATER PROJECT MANAGER, UPPER SAN PEDRO (ARIZONA)
    Based in Tucson or Sierra Vista, AZ., the Upper San Pedro Project Manager develops, manages, and advances freshwater conservation programs, plans, and methods focusing on...
  • CAMPAIGNS DIRECTOR
    Southeast Alaska Conservation is hiring. Visit https://www.seacc.org/about/hiring for info. 907-586-6942 [email protected]
  • FINANCE & GRANTS MANAGER
    The Blackfoot Challenge, located in Ovando, MT, seeks a self-motivated, detail-oriented individual to conduct bookkeeping, financial analysis and reporting, and grant oversight and management. Competitive...
  • WADE LAKE CABINS, CAMERON MT
    A once in a lifetime opportunity to live and run a business on the shore of one of the most beautiful lakes in SW Montana....
  • CONTRIBUTING EDITOR, BOOKS, CULTURE AND COMMENTARY (PART-TIME, CONTRACT)
    High Country News is seeking a Contributing Editor for Books, Culture and Commentary to assign and edit inquisitive, inspiring, and thought-provoking content for HCN in...
  • STATEWIDE COMMUNITY ORGANIZER
    ABOUT US Better Wyoming is a nonprofit, nonpartisan advocacy organization that educates, organizes, and mobilizes Wyoming residents on behalf of statewide change. Learn more at...
  • EXECUTIVE DIRECTOR
    TwispWorks is a 501(c)3 that promotes economic and cultural vitality in the mountainous Methow Valley, the eastern gateway to North Cascades National Park in Washington...
  • CLEAN ENERGY ADVOCATE OR DIRECTOR
    Location: Helena, Montana Type: Permanent, full time after 1-year probationary period. Reports to: Director of Policy and Legislative Affairs. Travel: Some overnight travel, both in-state...
  • PROFESSIONAL GIS SERVICES
    Custom Geospatial Solutions is available for all of your GIS needs. Affordable, flexible and accurate data visualization and analysis for any sized project.
  • DEVELOPMENT DIRECTOR
    Restore Hetch Hetchy, a 501 (c)(3) nonprofit organization, seeks experienced development professional to identify and engage individuals and institutions who are inspired to help underwrite...
  • PUBLIC LANDS COUNSEL
    The successful candidate will be the organization's lead counsel on public lands issues, including reviewing federal administrative actions and proposed policy and helping to shape...
  • GUIDE TO WESTERN NATIONAL MONUMENTS
    NEW BOOK showcases 70 national monuments across the western United States. Use "Guide10" for 10% off at cmcpress.org
  • RARE CHIRICAHUA RIPARIAN LAND FOR SALE
    40 acres: 110 miles from Tucson: native trees, grasses: birder's heaven::dark sky/ borders state lease & National forest/5100 ft/13-16 per annum rain
  • ENVIRONMENTAL GEOPHYSICS
    "More Data, Less Digging" Find groundwater and reduce excavation costs!