A longer pollen season is associated with a warming climate
Scientists have long hypothesized and now confirmed that a warmer climate could increase the production of pollen and pose problems for people suffering from seasonal allergies and asthma. A study published in the March 8, 2011 issue of the Proceedings of the National Academy of Sciences documents how the ragweed pollen season has increased by as many as 13 to 27 days in northern latitudes since 1995.
Scientists evaluated approximately 20 years of climate data and pollen records at 10 locations throughout North America. Pollen records were obtained from the National Allergy Bureau in the United States and from Aerobiology Research Laboratories in Canada.
The climate data show a clear increase in the number of frost-free days and a shift in the delay of fall frosts. These changes in climate were significantly associated with a prolonged ragweed pollen season at northern latitudes above 44 degrees. Lower latitude stations in Texas, Oklahoma, and Arkansas did not show a significant increase in the duration of the pollen season.
The prevalence of allergic disorders has increased in the United States over the last 30 years, with estimated costs of approximately $21 billion per year. Scientists do not yet fully understand why allergic disorders are increasing – likely, there are multiple factors involved – but an increase in exposure to pollen due to climate change may be an important piece of that puzzle.