This allergy season could be worse than those of past years in the U.S., heavy snow and rain in many places, followed by a sudden shift to warm weather, have led to a profusion of tree pollen and mold.
A new study in the Proceedings of the National Academy of Sciences shows a link between warming temperatures and a longer ragweed pollen season. According to researchers led by Lewis Ziska of the U.S. Department of Agriculture, the ragweed season is now 27 days longer in the northernmost areas of North America, largely because winter starts later and ends earlier, extending the time for pollen-bearing plants to thrive. It's not the first piece of research to make the claim that global warming will worsen allergies, but it's the most detailed and it's peer-reviewed.
In general, allergy seasons have been getting longer and more challenging, although pollen counts and allergy attacks vary widely from region to region.