Monday, September 29, 2014 - 18:42 YT&Twebzine

Study: Heat waves sparked by climate change

Is Mother Nature out to get us, or are we out to get Mother Nature? Scientists report that human-caused climate change affected some -- but not all -- extreme weather in 2013.

     Human-caused climate change “greatly increased the risk for the extreme heat waves” according to scientists studying extreme weather events around the globe. But they added, “How human influence affected other types of events such as droughts, heavy rain events and storms was less clear, indicating that natural variability likely played a much larger role in these extremes.”
     Events studied included the California drought, the torrential downpours in Colorado and the South Dakota blizzard of 2013.
     The report, Explaining Extreme Events of 2013 from a Climate Perspective, examined 16 extreme weather and climate events around the world. It was published Sept. 29 as a supplement to the Bulletin of the American Meteorological Society. The report's editors included scientists from the National Oceanic and Atmospheric Administration. They found:

Nine analyses of extreme heat events “overwhelmingly showed that human-caused climate change is having an influence," the report said. "In some cases, events have become as much as 10 times more likely due to the current cumulative effects of human-induced climate change, as found for the Korean heat wave of summer 2013.”

Researchers were not as certain about the influence of man-made climate change on droughts, which they describe as “highly complex meteorological events.” Global warming contributed to the severity of drought in New Zealand, the report said. But research on the California drought did not find a clear link to human-caused climate change.

Scientists found no clear evidence of human influence in three intense storms: a “surprising winter-like storm during autumn in the Pyrenees, an extreme blizzard across the U.S. High Plains and Cyclone 'Christian' that delivered damaging winds across northern Germany and southern Denmark."

Prolonged cold waves have become less likely, the report noted. A cold wave in the United Kingdom in 2013 was “most remarkable … its probability of occurrence may have fallen 30-fold due to global warming.”