An anticipated extension of the pollen season may spell misery for millions.
If recent trends are any clue, future climate change will significantly extend the ragweed-pollen season, giving added grief to millions who suffer from hay-fever.
Lewis Ziska, a plant physiologist with the US Department of Agriculture in Beltsville, Maryland, and his colleagues looked at how meteorological changes between 1995 and 2009 affected the ragweed-pollen season at sites stretching from central Texas to south-central Saskatchewan1. At the southern end of this swath, the length of the pollen-generating season — which ends when the first frost of autumn kills the ragweed plant — was little changed in 2009 compared with 1995.
However, at latitudes above 44° N, the first frost was substantially delayed, resulting in a pollen season 13 to 27 days longer in 2009 than in 1995. The higher the latitude, the more the pollen season lengthened over time — a trend that is consistent with the Intergovernmental Panel on Climate Change projections that relative warming will increase with latitude.
References
Ziska, L. et al. Recent warming by latitude associated with increased length of ragweed pollen season in central North America. Proc. Natl Acad. Sci. USA. 10.1073/pnas.1014107108 (2011).
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Perkins, S. More hay-fever misery. Nature Clim Change (2011). https://doi.org/10.1038/nclimate1064
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DOI: https://doi.org/10.1038/nclimate1064
