My pollen allergies seem to be getting worse and worse. Is it me, or is pollen actually increasing?
—Walt Jipposson, Chicago
You are probably not mistaken, and a changing climate might be the cause. A recent study from the University of Utah has found that rising temperatures have both worsened and lengthened the pollen season across North America. Three decades of pollen-count data from 60 monitoring stations across North America showed that the pollen season starts 20 days earlier than in 1990, lasts ten days longer and involves 21 percent more pollen. The biggest increases were recorded in the Midwest and Texas. Higher temperatures keep plants producing pollen for a longer period and tend to increase pollen concentrations in the air.