The study, by a team of Wisconsin researchers, indicates that a trend toward extreme weather such as the monsoon-like rainfall events that occurred in many parts of the region this past spring is likely to aggravate the risk for outbreaks of waterborne disease in the Great Lakes region.
"If weather extremes do intensify, as these findings suggest, our health will be at greater risk," according to Jonathan Patz, a University of Wisconsin School of Medicine and Public Health professor of population health and an expert on the health effects of climate change.
A primary threat to human health, according to Patz, are the extreme precipitation events that overwhelm the combined urban storm water and sewage systems such as those in Milwaukee and Chicago, resulting in millions of gallons of raw sewage being diverted to Lake Michigan.
Adding to the risk throughout the region is the growing concentration of livestock operations where heavy rainfall can wash large amounts of animal waste into the rivers and streams that drain into the Great Lakes, the world's greatest concentration of fresh surface water.
"It's the perfect storm," noted Patz. "Deteriorating urban water infrastructure, intensified livestock operations, and extreme climate change-related weather events may well put water quality, and thereby our health, at risk," he added.
Climate change, scientists know, will prompt extremes of the hydrologic cycle, causing intensified precipitation as well as drought.
Using the best available computer climate models, the Wisconsin researchers found that southern Wisconsin is likely to experience a 10 to 40 percent increase in the strength of extremely heavy precipitation events, leading to greater potential for flooding and the waterborne diseases that accompany the high discharge of sewage into Lake Michigan.
According to Patz and Stephen Vavrus, a climatologist and director of the UW-Madison Center for Climatic Research, the new study points to a need to strengthen pubic health infrastructure and improve aging urban drinking water and sewage systems, and to improve land use planning to reduce the amount of runoff that occurs in urban areas during major precipitation events.
"This is where climate policy, land use policy and public health come together," said Patz.