Iowa scientists find increasing humidity

The climate change could affect people, animals and crops

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DES MOINES — The state’s signature summer humidity is no longer just an annoyance, it’s now a costly reminder that climate change needs to be addressed, a group of Iowa scientists said Wednesday.

Gene Takle, one of the architects of the 7th annual Iowa Climate Statement endorsed by 190 science faculty, researchers and educators from 39 Iowa colleges and universities, told a Statehouse news conference that “absolute humidity” — measured by dew-point temperature — has increased statewide by 8 to 23 percent since 1971 and scientists have “good evidence” that’s due to increased carbon dioxide in the atmosphere that’s likely to increase.

Takle, a professor of geological and atmospheric sciences in Iowa State University’s Department of Agronomy, said the conditions relate to the increase of springtime moisture from the Gulf of Mexico that settles along Eastern Iowa, resulting in higher humidity readings measured across all seasons at all long-term monitoring stations in Iowa.

“The increasing cost for flooding, mold, insects, mosquitoes, humidity-related health issues, grain drying, air conditioning, erosion, etc., are evidence that climate change in humidity already is having a negative impact on both public and private checkbooks,” Takle said,

Iowa has been a national leader in embracing renewable energy sources, he said, but factors outside the state’s boundaries and direct control are negatively impacting the state’s climate. “As long as we avoid making progress on reducing the atmospheric concentration of carbon dioxide, these effects are going to increase,” he said.

The latest statement issued by the Iowa scientists describes the impact of significantly higher humidity levels on people, animals, crops and infrastructure.

According to the scientists, there is evidence the frequency of intense rain has increased in Iowa over the past 50 years; there is a northward expansion of species formerly restricted by a colder climate that could disrupt natural ecosystems and introduce agricultural pests and diseases; and agriculture, human health and economic stability could be affected if greenhouse gas emissions continue to increase.

“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,” said Betsy Stone, a University of Iowa associate professor in areas of chemistry and biochemical engineering,

Stone pointed to monitoring data dating to 1971 indicating that average humidity increased by 23 percent in Dubuque, 14.8 percent in Burlington, 11.9 percent in Des Moines, 10.7 percent in Waterloo, 9.2 percent in Sioux City and 8 percent in Mason City. Similar data since 1973 showed humidity increases averaging 22. 2 percent in Cedar Rapids and 11.5 percent in Ottumwa.

“Increased levels of humidity create hazardous conditions for Iowa workers and sensitive populations through the danger of heat exhaustion and heatstroke. Asthma is worsened by higher levels of allergens in the air. And the cost of air conditioning homes and businesses to maintain comfort levels increases,” said Takle.

“For Iowa’s agriculture, increased warm‐season humidity leads to water‐logged soils during planting season, rising humidity also leads to longer dew periods and higher moisture conditions that elevate costs of drying grain. Increased nighttime temperatures coupled with humidity causes stress to crops, livestock and pets.”

Visit to view the 2017 statement and all previous Iowa climate statements

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