Minneapolis Star TribuneDuluth eyes rebuilding for a wetter climateMinneapolis Star TribuneOne of the biggest tasks facing Duluth in the aftermath of last week's historic flash flooding will be repairing the city's 400-mile storm-water removal...
Climate scientists say increasing precipitation, particularly from intense thunderstorms, is a symptom of ongoing climate warming, because warm air holds more water vapor than cooler air.
The Upper Midwest saw a 31 percent increase in "intense" rainfalls -- the statistical 1 percent events -- from 1958 to 2007, over previous decades, according to the National Climatic Data Center. Last Tuesday and Wednesday's Duluth rainfall, measuring from 7 to more than 10 inches across the city, was in some places nearly double what's regarded as Duluth's 1 percent-chance rainfall. That made it "next to impossible to plan for," Shaffer said.
But it's the smaller, increasingly frequent downpours that cities now need to plan for, many climatologists and community leaders say. In Minnesota, the frequency of 2-inch rainfalls doubled across the state from 1991 to 2010 over the previous long-term rate, even in the north, where cooler weather generally tempers severe storms, Seeley said.