Climate Change to Blame for Longer, More Severe Allergy Season

Researchers say rapid climate change has led to an at least 20-day extension of allergy seasons and an increase in the amount of pollen in the air. 

An electron microscopy image of ragweed pollen reveals the fine details of a type of microspore that researchers say is more prevalent in our air due to rapidly accelerating climate change. (Courtesy of Lewis Ziska)

(CN) — The acceleration of climate change is linked to a host of mounting health and safety challenges in communities around the world. Now, the current warming trend is also to blame for extended allergy seasons worldwide, according to a study released Monday that brings distressing news for those who struggle with seasonal allergies. 

Since the late 19th century, Earth’s average surface temperature has risen about 2.12 degrees Fahrenheit, according to data analyzed by NASA. Scientists attribute the spike in temperature to industry and human activity driving carbon dioxide emissions into the atmosphere.

Most of the warming Earth has experienced has occurred in just the last 40 years, according to the National Oceanic and Atmospheric Administration (NOAA) data, which also found that the seven most recent years have been the hottest on record. 

The years 2016 and 2020 are tied for the warmest years in recorded history, NOAA data show.

The study led by William Anderegg of the University of Utah School of Biological Sciences found that increasingly warmer temperatures and weather play an elevated role in lengthening the period where environmental conditions — namely the prevalence of airborne pollen — trigger allergic reactions in people.

“The strong link between warmer weather and pollen seasons provides a crystal-clear example of how climate change is already affecting peoples’ health across the U.S.,” Anderegg said in a statement released with the study. 

Researchers analyzed U.S. and Canada pollen data compiled by the National Allergy Bureau between 1990 and 2018.

Certified pollen counters in 60 stations across both countries collected and hand-counted airborne pollen and mold samples.

The analysis found that nationwide pollen levels increased by 21% since 1990 and that pollen seasons start at least 20 days earlier than normal, according to the findings published in the journal Proceedings of the National Academy of Sciences.

Researchers have found that warming temperatures are causing plants like the Rocky Mountain Columbine flower in southwestern Colorado to produce pollen earlier each year. (Courtesy of William Anderegg)

According to the study, which analyzed dozens of climate models, climate change can be attributed to nearly half of the pollen season lengthening and close to 8% of the increase in pollen production.

“Climate change isn’t something far away and in the future. It’s already here in every spring breath we take and increasing human misery,” Anderegg said. “The biggest question is: are we up to the challenge of tackling it?”

The findings suggest anthropogenic — or human-caused — climate change is triggering plants’ phenology — or internal reproductive cycles — to produce pollen earlier in the year.

“Advances in pollen season start date and increases in spring pollen integrals strongly support a phenological seasonal shift of pollen loads to earlier in the year,” the study said. “Long-term increases in pollen season length and annual pollen integrals indicate that exposure times to allergenic pollen as well as amount of pollen have increased significantly for North America in recent decades.”

Texas and midwestern U.S. states saw the largest increase in pollen production, mainly in tree pollen, the study said.

The change will mean those who struggle with seasonal allergies will face additional weeks of itchiness, drippy noses and other symptoms, the study said. 

But the issue has implications beyond being a seasonal nuisance; an increase in airborne pollen can trigger complications with respiratory health, worsen viral infections and affect students’ ability to perform well in school, the study said. 

Previous studies have probed the interplay between pollen production and surges in temperature and atmospheric carbon dioxide within greenhouse settings while others looked at certain locations experiencing longer allergy seasons or climate change’s effect on certain plants. 

The study led by Anderegg is the first to examine climate change’s role in shaping pollen production on a continental scale, according to researchers. 

“A number of smaller-scale studies — usually in greenhouse settings on small plants — had indicated strong links between temperature and pollen,” Anderegg said. “This study reveals that connection at continental scales and explicitly links pollen trends to human-caused climate change.”

Researchers did not immediately respond to a request for further comment on the study. 

The study was funded by the David and Lucille Packard Foundation, the National Science Foundation and the USDA National Institute of Food and Agriculture.

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