Story URL: http://news.medill.northwestern.edu/chicago/news.aspx?id=214257
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2012 Temperature Climate Map

 

Courtesy of NOAA

Higher than normal temperatures across the Midwest caused droughts in the region.    


Warmer Midwest winters cause drought

by Morgan Kauphusman
Jan 17, 2013


Last March, Chicagoans enjoyed unseasonably summer weather, but it came with a price: drought.

The unusually warm weather across the Midwest contributed to drought conditions still being felt by much of the region, according to new data from the National Oceanic and Atmospheric Administration. Higher temperatures last winter decreased snow accumulation and subsequent soil moisture retention.

“One of the big things in 2012 was the really warm March,” said Jake Crouch, a climate scientist at NOAA’s National Climatic Data Center. “It might have caused a lot of problems in the Midwest that led to an early start to the growing season. It laid the foundation for the drought.”

Nationwide 2012 was 1 degree warmer than 1998, the previous hottest year on record. It was also a record warm year in Chicago, tied with 1921, NOAA reported.

The temperature increase in the Midwest, which caused precipitation to fall as rain rather than snow, presented a problem for soil moisture levels. Rain tends to run off and evaporate quicker whereas snowpack melts slowly into the ground as it thaws throughout spring. Much of the soil dried out, causing major setbacks for many growers across the breadbasket, according to Crouch.

Illinois saw only 19.8 inches of snowfall during the 2011-12 winter season, which is 18.2 inches less than the average 38 inches of snowfall the state typically receives, according to NOAA. Climate scientists are troubled by last year’s numbers and the prospect of a prolonged drought if this winter does not yield more snow.

“We have been on the dry side this winter and last winter,” said Jim Angel, state climatologist at the Illinois State Water Survey. “There’s not much precipitation of any kind. In the short term it’s not a problem, but if we get to March and it’s still dry that could be a problem again.”

Lake levels for Lake Michigan are also affected by the warmer temperatures even in the winter, according to Angel. Milder winter weather conditions prevent the lake from accumulating ice cover, which makes it more susceptible to evaporation.

“I’m a little concerned that we’re not recovering as fast as we should, so when we get into the growing season we won’t have enough moisture,” Angel said.

Still, the higher temperatures nationwide during the summer months were especially surprising to scientists, such as Crouch. “We calculated the population that had at least 10 days with over 100-degree weather in 2012,” he said. “A third of the population experienced at least 10 days with over 100-degree weather.”

However, Angel said we are too far out for scientists to begin to predict how hot this summer will turn out to be. “Right now there’s nothing to indicate that we’re going to be too hot or not this summer,” he said. “When we get more into the spring it will signal what the summer will look like."