October blizzard in midwest not attributable to climate change, scientists find

Livestock still had their summer coats and were rain-soaked in pastures when the snowfall began. An estimated 45,000 head of livestock perished and utility line repairs, tree removal and other cleanup cost millions of dollars.

What are the chances of it happening again in changing climate conditions?

That's what South Dakota State University Extension climate field specialist Laura Edwards and state climatologist Dennis Todey tried to figure out. They had the help of science and operations officer Matthew Bunkers of the National Weather Service in Rapid City and associate professor John Abatzoglou and graduate student Lauren Parker, both of the University of Idaho Department of Geography.

"It was just an anomaly," Edwards said. "This type of early season blizzard is an outlier and is not any more likely to occur in the future due to a changing climate."

Such a storm occurs about once every 10 years, so it is not uncommon to get that much precipitation in a two- or three-day period in western South Dakota. But the timing of the 2013 early October blizzard created devastating impacts.

Computer models showed a reduction in what Edwards called "extreme precipitation events" in the fall season in western South Dakota when compared to climate conditions in the 1800s. However, she added, the results were not statistically significant.

The scientists compared the amount of water vapor in the air within the Sept. 19 to Oct. 19 time frame, two weeks before and after the 2013 storm. Water vapor in the atmosphere in the Rapid City area has increased by nearly 12 percent since 1966, explained Edwards, but that increase again was not statistically significant.

"This increase in water vapor has contributed to increasing total precipitation in the fall season, but does not necessarily mean an increase in extreme precipitation events," she added.

Using climate modeling techniques, the scientists found no consensus regarding whether the blizzard could be attributed to a changing climate. Their findings are part of an American Meteorological Society publication, Explaining Extreme Events of 2013 from a Climate Perspective.

"Climate change has not loaded the dice in any way for this early fall blizzard," Edwards said. "Individual events are very difficult to attribute to a changing climate."

More information can be found at: http://www2.ametsoc.org/ams/index.cfm/publications/bulletin-of-the-american-meteorological-society-bams/explaining-extreme-events-of-2013-from-a-climate-perspective/