Climate statement 2017: It's the humidity

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Water-logged spring soils, extreme rain events, mold, and mosquitoes are all expected to be more prevalent in Iowa due to a rarely discussed impact of climate change: increased 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.

Absolute humidity, which is typically measured by dew point temperature, increased in Dubuque during springtime by 23 percent from 1970 to 2017. In Cedar Rapids, humidity has increased 22.2 percent since 1973. Increases have been measured across the Midwest.

Humidity couples with temperature to create the “heat index” that is a measure of how hot it feels.

High levels of humidity create hazardous conditions for workers and sensitive populations through the danger of heat exhaustion and heatstroke. Allergic rhinitis and asthma are worsened by heightened exposures to mold and dust mite allergens in humid environments. There also is evidence for increased aggression and societal violence associated with hot, humid weather.

For 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 higher moisture conditions that elevate costs of drying grain, and increase many pests and pathogens harmful to growing plants and stored grain.

Increased moisture accelerates metal corrosion, rot and warping of wood, and peeling of paint.

Iowans should recognize the damaging effects of increased humidity rival those of higher temperatures and heavy precipitation, and create unique needs for adapting our infrastructure. We must all do more to mitigate the effects of climate change, by curtailing emissions of heat-trapping gases, improving energy efficiency, and increasing use of clean and renewable energy.

For more information about the Iowa Climate Statement 2017 visit

• Gene Takle is director of the ISU Climate Science Program. Betsy Stone is an associate professor at UI.

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