Is climate change affecting allergy season across the United States? Experts say it is.
In many parts of the country, the spring allergy season has already begun, with impacts — namely high pollen counts that can lead to runny noses and itchy eyes for approximately one in four adults — expected to extend into the summer months.
Now, a new report from non-profit Climate Central says that millions of Americans in most major cities are suffering from earlier, longer, and more disruptive allergy seasons amid the effects of human-caused climate change.
The analysis, which used data from the National Oceanic and Atmospheric Administration, said that a warmer and earlier spring has resulted in a longer growing season, giving plants more time to grow and release their allergy-inducing powder.
The freeze-free growing season between 1970 and 2024 was found to have extended by 20 days in 87 percent of the 198 cities they analyzed since 1970.
While all regions have seen their freeze-free growing seasons lengthen by at least 13 days on average since 1970, cities across America’s Northwest and Southwest have experienced the largest average change, increasing by 24 and 20 days, respectively.
“The freeze-free growing season increased the most in: Reno, Nev. (96 more days); Las Cruces, N.M. (66 more days); Medford, Ore. (63 more days); and Tupelo, Miss. and Myrtle Beach, S.C. (both 52 more days),” the report said.
And, cities in the South, Southeast, Ohio Valley, and Northeast have experienced the longest average freeze-free seasons, which are now at least 10 percent longer in 70 of the cities that were analyzed.
The analysis comes following a previous study that found human-caused warming was a primary driver of North American pollen seasons lengthening from 1990 to 2018.
Last year, the Department of Health and Human Services also noted that the changing climate has caused more frost-free days, warmer seasonal air temperatures, and more carbon dioxide in the atmosphere that “may lead to both higher pollen concentrations and earlier and longer pollen seasons.“
Data from the National Phenology Network indicates that the start of spring has, on average, occurred earlier in the contiguous U.S, since 1984, and that total pollen amounts increased up to 21 percent between 1990 and 2018. The greatest increases were recorded in Texas and the Midwest.
“Some of these changes in pollen due to climate change could have major impacts on human health such as increasing individuals’ exposure to pollen and their risk of having allergy and/or asthma symptoms,” it said.
Climate Central also tied these changes to carbon dioxide pollution: a prevalent greenhouse gas contributing to the warming of Earth’s atmosphere.
“With continued high rates of CO2 pollution, the U.S. could face up to a 200% increase in pollen production by the end of this century, according to a 2022 study,” it said.
