New research has shown that pollen season has both intensified and lengthened across North America due to human-caused climate change. Pollen season starts up to 20 days earlier and lasts up to 10 days longer compared to 30 years ago. The study also found out that pollen concentration rose to 20.9%. Numerous factors such as changes in temperature, rainfall, frost days, and even carbon dioxide concentrations were looked at. The scientists discovered that the increase in average annual temperatures was the biggest factor.

The results are in line with Climate Central’s 2019 research brief, which found that global warming extends the freeze-free season, allowing plants more time to grow, flower, and produce pollen. At the same time, some plants producing allergenic pollen develop even more of it as CO2 levels continue to increase, studies showed. “There’s an enormous body of research on how climate change is already affecting our health. Our study fills in a key piece connecting climate change to pollen, which is one of the largest driver of asthma, allergies, and respiratory health problems,” according to William Anderegg, an assistant professor of biology at The University of Utah and lead author of the study.