For many central Iowans, the reality of a changing climate was all too evident this past weekend with flooded basements, stranded motorists and water rescues. Many cities around Polk County were deluged with up to 10 inches of rain in just a few hours. Before we write this off as an extreme weather event or an anomaly, we need to look at the long term trends that predicted this latest weather catastrophe.

Climate scientists are reluctant to link one extreme weather event to a changing climate. However, the accumulating climate evidence suggests intense rain events like the one this weekend are becoming more common in Iowa. According to Iowa scientists, there is evidence that the frequency of intense rain has increased in Iowa over the past 50 years.

The flooding this weekend is the latest reminder that Iowa is vulnerable in multiple respects to a rapidly changing climate. This isn’t about distant melting glaciers or polar bears. It’s about the real climate flood risk posed to Iowans now.

Former State Climatologist Harry Hillaker described some of the changes Iowans should expect from a changing climate. Hillaker says that in the last 50 or 60 years, Iowa has had about a 25 percent increase in precipitation, meaning an increase of about 5 or 6 inches of rainfall a year.

For farmers that may seem like a positive. Yet wetter springs delay planting and intense rainfall events lead to greater erosion and loss of nutrients. Increased runoff contributes to the growing dead zone in the Gulf of Mexico.

The 7th annual Iowa Climate Statement issued on August of 2017 focused on escalating humidity levels in Iowa and how that translates to increased precipitation. The report endorsed by 190 science faculty, researchers and educators from 39 Iowa colleges and universities was entitled, “It’s not the heat, it’s the humidity.”

“Discussions about climate change in Iowa usually focus on changes in temperature and rainfall. However, the rise in ‘absolute humidity’ (moisture in the air) is likely to become the most pervasive factor in climate change across the state,” the report said. “Absolute humidity, which is typically measured by dew point temperature, increased in Dubuque during springtime by 23% from 1970 to 2017. (Statewide humidity has increased from 8-23 percent). Increases in humidity have been measured across the Midwest and in Iowa across all seasons and at all long‐term monitoring stations.”

“For Iowa agriculture, increased warm‐season humidity leads to increased rainfall, extreme rain events, water‐logged soils during planting season, soil erosion, and runoff of chemicals to waterways. Rising humidity also leads to longer dew periods and higher moisture conditions that elevate costs of drying grain and increase populations of many pests and pathogens harmful to both growing plants and stored grain. Increased nighttime temperatures coupled with humidity causes stress to crops, livestock and pets and, in extreme cases, heat stress can cause loss of life.”

The earth is warming due to increased greenhouse gas emissions, and the climate models for Iowa suggest both increased frequency and increased intensity of precipitation. Here in central Iowa we have just witnessed the devastating consequences of an extreme rain event. The damage to homes, businesses, infrastructure and loss of life should be a call to action.

Iowa scientists are warning us that similar extreme weather events will continue and become more frequent in the future unless we reduce the warming effect of greenhouse gas emissions. The climate clock is ticking and this weekend’s flooding was the latest alarm.


by Rick Smith
Posted 7/3/18

5 thoughts on “Iowa Flooding Signals A Changing Climate

  1. Thanks for sharing these poignant facts. Of course it will take time to reverse the impacts we have created with climate change emergence, in the meantime we have another strategy that we must consider—restoring soil health! As Gabe Brown has demonstrated on his own farm in North Dakota, after implementing practices that brought the soil on his farm back to life, his soil now absorbs “ten inches of rainfall per hour” instead of the “1/2 inch per hour” which is all it absorbed before—and the practices he implemented to accomplish this remarkable result are already well known—-reduce tillage, include cover crops, and diversify production systems. Implementing such changes, and providing farmers with the financial incentives to implement them, could make Iowa a much more “resilient” place to live in for all of us while we begin the longer term process of implementing the changes we need to make to reduce the longer-term climate change issues we have caused on our lovely planet earth.

  2. People with compromised lungs or other beathing issues are having trouble with the humidity increase, too. I use myself as a case-in-point.
    And with more severe weather in all four seasons, it gets tougher. Iowa is (still) in the forefront in non-polluting energy production; we MUST remain there. Farms must adapt, too (as Mr. Kirschenmann so ably points out) to different techniques, especially ones that reduce the amount of processed fertilizers and herbicides. And they must learn how to control and mitigate their waste. Our water is a precious commodity, and it is not unlimited; we must be stewards of the land (Iowa has indeed been blessed with wonderful land!) and water.

  3. Researchers now know that most Iowa cropfields have topsoil that is so degraded that the fields would continue to leak nutrient pollution into rivers and lakes even if farmers quit using artificial fertilizer altogether. Our biggest problem isn’t fertilizer overuse, it’s degraded topsoil. Fred Kirschenmann is right — restoring soil to health is critical. Iowa topsoil has lost most of the soil organic matter that was built up during many centuries under tallgrass prairie, organic matter that used to hold huge amounts of rainfall and nutrients in place and was made up of complex carbon. As a soil-expert friend pointed out, Iowa doesn’t have a nitrogen problem — what it really has is a carbon problem.

    Every single Iowan, adult and child, should at some point watch a slake test. Watching a single good slake test that takes only two minutes is a major education in why our water quality is currently so bad and how it can be made so much better.

  4. These warnings are based on scientific evidence. Ironically, corporations that rely on scientific foundations are on the sidelines with agricultural reform. As long as corporate profits drive agriculture with the absence of mandates or regulations the situation will only get worse. Without political change reversing the unfettered capitalism of “conservative” politicians we are doomed for more of the same.

    1. And the bilgewater that certain Iowa industrial-ag interest groups are spouting is an insult to common sense. First they proclaim that all farmers are extremely eager to do the right things for water, and then they moan that actually requiring farmers to do the right things for water would be utterly and completely horrible, and then they do their proclaiming and the moaning at the same time. Seriously?

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