A new study finds that pollen season and its awful nasal drips is coming earlier and hitting harder — and that’s because of global warming. Monday’s study is the first to use accepted scientific methods to attribute worsening allergies in the United States directly to human-caused climate change. The study finds that since 1990 pollen season has started about 20 days earlier in the U.S. and Canada and pollen loads are 21% higher. Pollen is nothing to sneeze at. Experts say asthma, often triggered by allergies, can cost the U.S. $80 billion a year with hospitalizations up and test scores dropping for pollen-hit students.