by Don Hofstrand, retired extension agricultural business specialist, agdm@iastate.edu and reviewed by Dr. Eugene Takle, retired professor emeritus Iowa State University
Iowa is warmer. It is approaching 1.5 degrees warmer today than it was in 1988. This does not mean that every year is warmer than the previous one. There is a considerable variation between years, but the overall trend is up.
This small increase in temperature may not seem like it could have a significant impact on climate. However, the difference in Earth’s temperature between now and the ice age when glaciers reached down as far as Des Moines is only about 10 to 12 degrees.
Northwest Iowa has warmed the most and Southeast Iowa the least. Minnesota, Wisconsin, Nebraska, and Missouri have all warmed faster than Iowa.
Winters have warmed more than any other season. Falls have warmed more than springs. Summers have essentially remained unchanged, but this is expected to change in the future. Also, nights have warmed faster than days.
The Midwest is projected to see the largest future increases in temperatures in the US. So, Iowa’s temperatures will likely ramp up. Five out of every 10 years, a five-day heat wave now averages 90 to 95 degrees in central Iowa.
By 2050, the average is expected to climb seven degrees to 97 to 102 degrees. Once every 10 years, temperature will spike 13 degrees higher, pushing the five-day heat wave to 103 to 108 degrees. In addition, day-to-day and season-to-season temperature variability is expected to increase.
Iowa’s annual precipitation has increased since the beginning of the 20th Century. This is due in large part to warmer waters in the Gulf of Mexico and the fact that warmer air can hold more moisture. Most of the wettest years on record have occurred since 1982. In the future, most of the increase in precipitation will come from wetter springs, with drier or little change in summers. However, summer precipitation will become more variable with longer stretches between rainfall events.
The intensity of rainfall events has also increased. Across the Midwest, very heavy rainfall events increased by 42% from 1958 to 2016. Iowa ranks fourth nationally in the number of floods since 1988. The increase in heavy rainfall events is expected to continue into the future.
Essentially, we are experiencing what the rest of the planet is experiencing. Wet areas are getting wetter, and dry areas are getting drier.
See the Ag Decision Maker website for more from this series.
