» For a more detailed assesment of Midwest climate risk, see "Heat in the Heartland: Climate Change and Economic Risk in the Midwest."

Midwest Map

The upper Midwest economy is dominated by commodity agriculture, with some of the most intensive corn, soybean, and wheat growing in the world.

A farmer surveys his dry pond bed in Ashley, Illinois

A farmer surveys his dry pond bed in Ashley, Illinois

Overall, the agricultural industry in this region includes more than 520,000 farms valued at $135.6 billion per year as of 2012, and the region accounts for 65% of national production of corn and soybeans alone. 18 For the Midwest, commodity agriculture is a crucial business, and the health and productivity of the agricultural sector is inextricably intertwined with climate conditions. Our research shows that under the “business as usual" scenario and assuming no significant adaptation by farmers, some states in the region, like Missouri and Illinois, face up to a 15% likely average yield loss in the next 5 to 25 years, and up to a 73% likely average yield loss by the end of the century. Assuming no adaptation, the region as a whole faces likely yield declines of up to 19% by mid-century and 63% by the end of the century.

Yet while the agricultural industry will clearly be affected by climate change, it is also probably the best equipped to manage these risks. Farmers have always adapted to changing weather and climate conditions, with adaptation and flexibility built into their business models. Armed with the right information, Midwest farmers can, and will, mitigate some of these impacts through double-and triple-cropping, seed modification, crop switching and other adaptive practices. In many cases, crop production will likely shift from the Midwest to the Upper Great Plains, Northwest, and Canada, helping to keep the U.S. and global food system well supplied. However, this shift could put individual Midwest farmers and farm communities at risk if production moves to cooler climates.

The projected increase in Midwest surface air temperatures won't just affect the health of the region's crops; it will also put the region's residents at risk. Over the past 40 years, the Midwest experienced only 2.7 days on average over 95°F. If we stay on our current climate path, the average Midwest resident will likely experience an additional 7 to 26 days above 95°F each year by mid-century, and 20 to 75 additional extreme-heat days—potentially more than 2 additional months per year of extreme heat—by the end of the century. On the other hand, the region will also experience fewer winter days with temperatures below freezing.

But the real story in this region is the combined impact of heat and humidity, which we measure using the Humid Heat Stroke Index, or HHSI. The human body's capacity to cool down in the hottest weather depends on our ability to sweat, and to have that sweat evaporate on our skin. Sweat keeps the skin temperature below 95°F, which is required for our core temperature to stay around 98.6°F. But if the outside temperature is a combination of very hot and very humid—if it reaches a HHSI of about 95°F—our sweat cannot evaporate, and our core body temperature can rise until we actually collapse from heat stroke. Even at an HHSI of 92°F, core body temperatures can get close to 104°F, which is the body's absolute limit.

To date, the U.S. has never experienced heat-plus-humidity at this scale. The closest this country has come was in 1995 in Appleton, Wisconsin, when the HHSI hit 92°F. (At the time, the outside temperature was 101°F and the dew point was 90°F.) The only place in the world that has ever reached the unbearable HHSI of 95°F was Dhahran, Saudi Arabia, in 2003 (outside temperature of 108°F, dew point of 95°F). Our research shows that if we continue on our current path, the average Midwesterner could see an HHSI at the dangerous level of 95°F two days every year by late century, and that by the middle of the next century, she or he can expect to experience 20 full days in a typical year of HHSI over 95°F, during which it will be functionally impossible to be outdoors.

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18 U.S. Department of Agriculture, 2007 Farm and Ranch Irrigation Survey, Vol. 3, (2010), available at http://www.agcensus.usda.gov/Publications/2007/Online_Highlights/Farm_and_Ranch_Irrigation_Survey/fris08.pdf.