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Research links specific 2017 extreme weather events to climate change

  • According to the seventh annual special report by the Bulletin of the American Meteorological Society (BAMS) probing the causal links between rising global temperatures and extreme weather events, issued last month, climate change made the Northern Great Plains drought of 2017 some 1.5 times more likely and greatly enhanced its intensity by driving long-term reductions in soil moisture.
  • For the second year in a row, scientists were able to identify specific extreme weather events that cannot be explained without factoring in Earth’s warming global climate.
  • A team of 120 scientists from 10 different countries used historical observations and model simulations to produce the 17 peer-reviewed analyses collected in the BAMS special report examining extraordinary weather events from around the globe that were made more likely or exacerbated by anthropogenic (human-caused) climate change.

Throughout the spring and summer of 2017, a “flash drought” developed quickly in the Northern Great Plains region of the United States, which encompasses the states of Montana and North and South Dakota. The U.S. Drought Monitor recorded little to no drought conditions in the region on May 2 of that year, but, by August 1, abnormally high temperatures and little rainfall had caused a widespread and extreme drought.

The drought led to an unusually intense wildfire season — at one point, Montana suffered from 21 large wildfires that covered 438,000 acres. It also caused losses for cattle ranchers and farmers that were so severe some counties were declared disaster areas. All told, some $2.5 billion in damages were caused by this single extreme weather event — one of 16 “billion dollar disasters” to occur in the U.S. in 2017.

According to the seventh annual special report by the Bulletin of the American Meteorological Society (BAMS) probing the causal links between rising global temperatures and extreme weather events, issued last month, climate change made the Northern Great Plains drought of 2017 some 1.5 times more likely and greatly enhanced its intensity by driving long-term reductions in soil moisture.

For the second year in a row, scientists were able to identify specific extreme weather events that cannot be explained without factoring in Earth’s warming global climate. A team of 120 scientists from 10 different countries used historical observations and model simulations to produce the 17 peer-reviewed analyses collected in the BAMS special report examining extraordinary weather events from around the globe that were made more likely or exacerbated by anthropogenic (human-caused) climate change.

One of the research papers in the report found that abnormally warm sea surface temperatures off the coast of Africa could not have occurred in Earth’s pre-Industrial climate, and that those warmer waters doubled the likelihood of a 2017 drought in East Africa that caused food shortages for more than 6 million people in Somalia.

Other papers determined that climate change made the pre-monsoon rainfall that caused flooding in northeast Bangladesh 100 percent more likely and the extreme rainfall that led to flooding in southeastern China in June 2017 200 percent more likely. Heatwaves as hot or hotter than the one in the Euro-Mediterranean region in 2017 are three times more likely now than they were in 1950, another paper concludes, while forecasting a 10 percent chance of such a heatwave recurring in any given year.

The BAMS report also includes analyses of ocean heat events such as the intense heatwaves in the Tasman Sea in 2017 and 2018 that were found to be “virtually impossible” without manmade global warming.

“These attribution studies are telling us that a warming Earth is continuing to send us new and more extreme weather events every year,” Jeff Rosenfeld, the editor in chief of BAMS, said in a statement. “The message of this science is that our civilization is increasingly out of sync with our changing climate.”

Martin Hoerling, a NOAA research meteorologist who also served as a special editor for BAMS, said that the events studied in the special report may have occurred across six continents and two oceans over the course of a full calendar year, but that they are all connected just the same.

“These studies confirm predictions of the 1990 First IPCC report, which foresaw that radical departures from 20th century weather and climate would be happening now,” Hoerling said in a statement. “Scientific evidence supports increasing confidence that human activity is driving a variety of extreme events now. These are having large economic impacts across the United States and around the world.”

The Rice Ridge Fire in Montana was started by a lightning strike on July 24, 2017 and became a megafire on September 3. Photo via Wikimedia Commons.

CITATION

• American Meteorological Society. (2018). Explaining Extreme Events in 2017 from a Climate Perspective. Bulletin of the American Meteorological Society, 99 (12).