Get Out the Kleenex — Climate Change Lengthens Allergy Season

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For about 36 million Americans with seasonal allergies, torture time is just around the corner. As spring flowers, the pollen will flow, resulting in nasal congestion, red itchy eyes and overall awfulness. It’s not just cosmetic either — for an estimated 23 million Americans with asthma, allergies can pose a serious health threat. Nor is it cheap — allergies and allergy-driven asthma cost the U.S. an estimated $32 billion a year.

Bad news, snifflers — it’s going to get worse. A new study in the Proceedings of the National Academy of Sciences shows a link between warming temperatures and a longer ragweed pollen season. According to researchers led by Lewis Ziska of the U.S. Department of Agriculture, the ragweed season is now 27 days longer in the northernmost areas of North America, largely because winters starts later and ends earlier, extending the time for pollen-bearing plants to thrive. It’s not the first piece of research to make the claim that global warming will worsen allergies, but it’s the most detailed and it’s peer-reviewed. (More on Asthma Hits Poor Minorities Worst in California)

As Kim Knowlton — a scientist at the Natural Resources Defense Council and a professor at Columbia University — wrote in a blog post, the evidence is strong:

We knew already that springtime was coming 10 to 14 days earlier than it did 20 years ago. But this new work measures the length of the ragweed pollen season in the US for the first time, and finds it’s getting longer as temperatures rise, especially the farther north you go. (States like Minnesota and Wisconsin showed some of the strongest effects.) If these warming trends continue (as they’re projected to) under a changing climate, the health of people with severe allergies or asthma could really suffer.

The PNAS researchers examined ragweed and daily temperature data from Canada and the U.S. at 10 different latitudes. In eight of those areas — and in all seven spots north of 40 degrees latitude, around Philadelphia — the ragweed season increased between 1995 and 2009. (More on Can Overuse of Antibacterial Soap Promote Allergies in Kids?)

It makes sense that the increases in the allergy season would be more extreme the farther north the researchers looked. Climatologists have long predicted that warming would be most intense at the poles, and so far the data has borne them out. So it was with the PNAS study — in LaCrosse, Wis., ragweed was in the air 13 days longer in 2009 than 1995, and in Saskatoon, Saskatchewan, the season was 27 days longer. By contrast, in southern cities like Georgetown, Texas, the allergy season was actually four days shorter. That’s strong proof, as Ziska told DiscoveryNews:

I was surprised to see the signal as strong as it was. I thought we might see something fairly weak, but I was surprised that even in the last couple of decades we could see things.

Of course, 14 years is still a fairly short period of time for researchers to draw long-term conclusions about how climate change will impact allergies in the future. But there’s already been a doubling of asthma in the U.S. since 1980, and a longer and earlier spring — and more pollen — won’t help, as Paul Beggs, an environmental scientist at Australia’s Macquarie University, points out:

The significant lengthening of the ragweed pollen season, particularly in the higher latitudes of North America, over the last 15 or so years, revealed in this research, adds to the likelihood that climate change has for some time now already been having an adverse impact on human health

Given the unlikelihood of climate change being curbed any time soon, I’ve got one word for allergy suffers: Claritin.

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Allergies Worse Than Ever? Blame Global Warming