Behind the Forecast: Is allergy season getting longer

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.
Updated: May. 14, 2021 at 9:14 AM EDT
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Since 1970, the average number of days above freezing has steadily increased in Louisville.
Since 1970, the average number of days above freezing has steadily increased in Louisville.(Climate Central)

LOUISVILLE, Ky. (WAVE) - Springtime brings the dreaded allergy season. More than 50 million Americans deal with allergies each year, according to the Asthma and Allergy Foundation of America (AAFA), Climate change may play a role in the seemingly longer Spring allergy season.

A 2020 study published in the Proceedings of the National Academy of Sciences of the United States of America found that “anthropogenic climate change” has made pollen seasons in North America worse. These researchers believe that “climate-driven pollen trends” will cause significant impacts on respiratory health in the coming decades. Research determined that the length of pollen season and pollen concentrations have both increased. The research used data from 60 North American stations from between 1990 to 2018.

With Fall-like temperatures lingering later and Spring-like temperatures seemingly arriving earlier each year, the growing season and pollen season both appear to be longer. In fact, according to data from Climate Central, Louisville’s average Spring temperature has increased 3.7° between 1970 and 2020. Louisville on average sees 14.7 more days with temperatures above normal in the Spring. According to data, Louisville’s growing season has been extended by 17 days. Bend, Oregon, and Reno, Nevada have seen their growing season extended by 99 days!

Carbon dioxide has a significant impact on pollen production.
Carbon dioxide has a significant impact on pollen production.(Climate Central)

The amount of carbon dioxide in the air influences pollen levels because it helps to spur plant growth. A 2014 study found that grass pollen levels doubled when carbon dioxide levels increased from 400 ppm (where we are now) to 800 ppm. Some reports have found that those higher levels were possible by the end of the century if current trends continued.

Longer growing seasons and higher pollen concentrations can and would have a significant impact on those with allergies or asthma.

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