Climate change is causing allergy seasons to start earlier, last longer, and be more intense, according to a new study from the University of Utah.
The study, published in the Proceedings of the National Academy of Sciences, shows that pollen seasons in North America are, on average, starting 20 days earlier, lasting 10 days longer, and feature 21% more pollen than 1990 levels.
The research found that human-induced climate change played a significant role in the lengthening of the pollen season, and a partial role in the increasing pollen counts.
Pollen allergies are a nuisance for many people, but they can also have more serious health effects. In Australia, there have even been deaths associated with high pollen – including during a thunderstorm asthma event in Melbourne in 2016.
“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.,” says William Anderegg, the lead researcher on the study.
While past research has found that higher temperatures and carbon dioxide levels cause more pollen production, this study shows that pollen seasons are increasing on a larger scale as the weather warms.
“A number of smaller-scale studies – usually in greenhouse settings on small plants – had indicated strong links between temperature and pollen,” Anderegg notes. “This study reveals that connection at continental scales and explicitly links pollen trends to human-caused climate change.”
The team compiled measurements between 1990 and 2018 from 60 pollen count stations across the United States and Canada, maintained by the National Allergy Bureau. These stations collect airborne pollen and mould samples, which are then hand-counted by certified counters.
The results showed that climate change alone could account for roughly half of the pollen season lengthening and around 8 percent of the pollen amount increasing. By splitting the study years into two periods, 1990-2003 and 2003-2018, the researchers found that the contribution of climate change to increasing pollen amounts is accelerating.