Get out your tissue box: researchers find that global warming extends the pollen season in northern latitudes.

3/11/11

Credit: Sue Sweeney/ Wikimedia Commons

Researchers studying ragweed (Ambrosia spp.), one of the worst allergy-causing plants, particularly for the summer and fall season, have found that its pollen season has been extended, due to warming temperatures in the upper latitudes.  In northern states, such as Wisconsin and Minnesota, the ragweed pollen season has been extended by roughly two weeks (13-16 days).  Further north, in areas of Canada, such as Winnipeg and Saskatoon, the ragweed season has been stretched by almost one month (25-27 days)!

Their findings are consistent with the United Nations' Intergovernmental Panel on Climate Change (IPCC) assessment that current and projected increases in global warming are not uniform and depend, rather, on latitude and elevation.  The researchers looked at pollen counts and weather data from 10 locations across the North American continent, from as far south as Georgetown, Teaxs to as far north as Saskatoon, Canada over a 15 year period (1995-2009).  As latitude increased, they observed an increase in the usual length of the growing season (increase in the frost-free period), as well an a change in the number of days to first frost.  Upper latitudes are warming faster than mid-latitudes and the researchers found that changes in the length of the ragweed pollen season were in proportion to these warming differences.

The impact of study goes beyond a couple of sniffles and sneezes.  The authors cite that ragweed may cause more seasonal allergic reactions than all other plants combined.  And for those who suffer from asthma, allergies can oftentimes trigger asthma or make it worse.   With a now longer pollen season and increased pollen counts, the number of people affected by allergic reactions to ragweed could increase dramatically.


Sharinne Sukhnanand

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These briefs are part of a weekly series of updates to the publication: Climate Change: Past, Present, and Future.  The entire series can be found here.