Global warming: Severe Midwest storms increasing
Loretta Lohman
Global warming: Severe Midwest storms increasing
Rains, flooding threaten water infrastructure
Climate researchers say they’ve documented an increasing number of severe storms in the Midwest most likely linked with global warming.
SUMMIT COUNTY — A startling increase in severe storms is straining water infrastructure and threatening public health and safety, according to a report from the Rocky Mountain Climate Organization and the Natural Resources Defense Council.
The number of those big storms has doubled in the last 50 years, with greatest increase in Wisconsin, Indiana and Michigan.
“Global studies already show that human-caused climate change is driving more extreme precipitation, and now we’ve documented how great the increase has been in the Midwest and linked the extreme storms to flooding in the region,” said Rocky Mountain Climate Organization president Stephen Saunders,” suggesting that it might not be accurate to simply characterize the storms as natural disasters. “And if emissions keep going up, the forecast is for more extreme storms in the region,” he said.
“This report confirms what most of us in the Midwest have known for a while; violent storms are becoming more frequent,” said NRDC senior policy analyst Karen Hobbs. “And the nation’s crumbling water infrastructure just makes the problem worse. Most of our communities were not designed to handle the volume of water dumped by these epic storms. But green infrastructure solutions, such as green roofs, street trees and rain gardens, literally capture rain where it falls, helping prevent flooding and providing communities with greater resiliency to these ferocious storms.”
The report’s key findings include:
- Since 1961, the Midwest has had an increasing number of large storms. The largest of storms, those of three inches or more of precipitation in a single day, increased the most, with their annual frequency having increased by 103 percent over the roughly half century period through 2011. For storms of at least two inches but less than three inches in a day, the trend was a 81 percent increase; for storms of one to two inches, a 34 percent increase. Smaller storms did not have a significant increase.
- The rates of increase for all large storms accelerated over time, with the last analyzed decade, 2001- 2010, showing the greatest jumps. For the largest storms, in 2001-2010 there were 52 percent more storms per year than in the baseline period.
- The frequency of extreme storms has increased so much in recent years that the first 12 years of this century included seven of the nine top years (since 1961) for the most extreme storms in the Midwest.
- With more frequent extreme storms, the average return period between two such storms has become shorter. In 1961-1970, extreme storms averaged once every 3.8 years at an individual location in the Midwest. That is two to four times more frequent than a major hurricane making landfall at a typical location along the U.S. coast from North Carolina to Texas. By 2001-2010, the average return period for Midwestern extreme storms at a single location was down to 2.2 years—or four to eight times more frequent than landfalling major hurricanes.
The report also presents new evidence linking extreme storms in the Midwest to major floods, the region’s most costly regularly occurring natural disasters. The new analysis shows that the two worst years in the Midwest for storms of three inches or more per day were 2008 and 1993, the years with the Midwest’s worst floods in some 80 years, which caused $16 billion and $33 billion in damages and rank, among the nation’s worst natural disasters. The report presents new evidence linking the 2008 flooding to extreme storms, showing that in areas with the worst flooding 48 percent of the local precipitation came from extreme storms.
In 2010, which ranked fourth among years in regional extreme-storm frequency, Iowa alone had $1 billion in agricultural losses from extreme storms. In 2011, which ranked fifth, Midwestern flooding caused $2 billion in damages. This shows how the Midwest is increasingly vulnerable to flooding if extreme precipitation continues to increase with human-caused climate change, as scientists consistently project will happen.
“This study’s results highlight real issues that have already caused significant pain and suffering in Milwaukee,” said Kevin Shafer, executive director of the Milwaukee Metropolitan Sewage District. “We have learned that we can no longer sit on our hands and hope that extreme rainfall events are not going to happen. We need to explore new ways to soften the impacts of these events and to better protect our residents,” Shafer said.
“In Milwaukee, we are adding green infrastructure to our landscape, reinforcing our grey infrastructure, converting to renewable energy for all our wastewater facilities, and educating our public about what they can do be better prepared for flooding. In these tight economic times, it is not a popular message, but, having lived through it, we understand that it is better than the alternatives,” he added.
-- Loretta Lohman, Ph.D. Nonpoint Source Outreach Coordinator Colorado State University Colorado Water Institute 3375 W. Aqueduct Avenue Littleton, CO 80123 lorett...@gmail.com loretta...@colostate.edu 303-549-3063 www.npscolorado.com