Study confirms more frequent heavy rains in Midwest

A scientific report issued Wednesday confirms what most Iowans have long known or suspected: that heavy rains have been falling with increasing frequency, causing disastrous flooding.

Incidences of the most severe downpours have doubled during the past 50 years in eight Midwest states, according to a report by the Rocky Mountain Climate Organization and the Natural Resources Defense Council.

Among the eight states in the study, Iowa registered the lowest impact with a 32 percent increase in the frequency of rainfalls totaling 3 or more inches in 24 hours. The other states, with their percentage increase in parentheses, are Indiana (160), Wisconsin (203), Missouri (81), Michigan (180), Minnesota (104), Illinois (83) and Ohio (40).

“The increases were much more than we expected,” said Stephen Saunders, president of the Rocky Mountain Climate Organization and the report's lead author.

The new study, unlike others preceding it, includes data from 2008 through 2011, he said.

For the past several years, Iowa climate scientists – including Eugene Takle and Christopher Anderson, both of Iowa State University - have been documenting and warning Iowans about the increase in extreme rainfall events.

Saunders said the trend toward more frequent extreme storms accelerated during the past decade.

In the Midwest, the first 12 years of this century included seven of the nine top years (since 1961) for the most extreme storms, according to Saunders.

For the June 2008 storm that swamped Cedar Rapids and other Iowa locales, 48 percent of the floodwater fell in the form of extreme rainfall events, he said.

The study also found that the average interval between extreme storms at an individual Midwest location had shrunk from 3.8 years in the 1960s to 2.2 years during the past decade.

Although Saunders acknowledged that localized data does not constitute proof of human-caused climate change, he said that other global studies have established that connection to the satisfaction of most scientists.