Climate change is extending allergy season and making allergies worse, according to a report by Climate Central, impacting the nearly 20 million Americans who suffer allergies. Laboratory research shows elevated CO2 levels cause some plants, like ragweed, to increase pollen production. And, according to MacArthur grantee Climate Central, regional allergy seasons have lengthened by an average of two weeks since 1970 because fewer days with frost mean a longer growing season.
