Longer, More Intense Pollen Seasons Driven by Human-Led Climate Change, Study Says

Compared with pollen season in 1990, today's pollen season is starting earlier and lasting longer, largely because of human-caused climate change, researchers said.

Climate change created by humans is creating pollen seasons that start earlier in the year and last longer and is partly to blame for the increased amount of pollen concentrations, according to a new analysis from university researchers.

Although the paper did not directly analyze health impacts, the authors, from the University of Utah, University of California, Rutgers University, the Hackensack Meridian School of Medicine, Kean University, Boston University, and Columbia University, said they “hypothesize that climate-driven changes in spring and/or annual pollen integrals would have important implications for spatial and temporal patterns of allergy and asthma prevalence and associated medical costs.”

The paper, published this week in the Proceedings of the National Academy of Sciences, looked at pollen trends on a continental scale and included simulations of 22 climate models. Smaller, previous studies have found that increases in temperature and atmospheric carbon dioxide can cause more pollen production or a worsening of pollen seasons. This study looked at the issue on a larger scale and attempted to quantify the effect of climate change.

The researchers analyzed data from 60 pollen stations (mainly in the United States, 2 in Canada) from 1990 to 2018. Combining that information with observational climate datasets as well as the climate simulations, they aimed to answer 3 questions: what are the long-term pollen trends? How much of a role does changing temperature, precipitation, and increasing carbon dioxide play in those metrics? How much of the change can be attributed to human-caused climate change?

The stations, maintained by the National Allergy Bureau, collect airborne pollen and mold samples. The statistically significant findings showed that pollen season in North America, compared with 1990, is:

  • Lasting 10 days longer
  • Starting 20 days earlier
  • Has 21% more pollen concentration
  • Affecting Texas and the Midwest the most
  • Increasing the amount of tree pollen the most

The length of pollen season, as well as the increased concentrations of pollen, are most closely linked with global warming. Human-led climate change was a factor in about 50% of the change in pollen season and about 8% of the increase in pollen concentrations.

In addition, the overall study period was divided into 1990-2003 and 2003-2018, and the researchers found that the contribution of climate change to increasing pollen amounts increased faster in the most recent timeframe.

Scientists have been warning about the impact of climate on health for years. Air pollution is a known factor for respiratory diseases like asthma, pneumonia, and others. It has also been linked to lung infections, especially in small children.

Last month, 4 cardiovascular organizations issued a joint statement urging action to mitigate the effect of air pollution on health. In one of his first actions after taking office, President Joe Biden signed executive orders announcing sweeping reforms to the previous administration’s climate policies, including rejoining the Paris climate accord, cancelling the Keystone XL pipeline, pausing oil and gas leasing on federal land, and adding an office devoted to climate and health to HHS.

Asthma and allergies are one of the leading causes of illness and health care utilization, the researchers noted.

"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.," William Anderegg, PhD, lead author and an assistant professor of the University of Utah School of Biological Sciences, said in a statement.

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

Reference

Anderegga WRL, Abatzogloub JT, Andereggc LDL, Bielorye L, Kinney PL, Ziskaim L. Anthropogenic climate change is worsening North American pollen seasons. Proc Natl Acad Sci U S A. Published online February 8, 2021. doi:10.1073/pnas.2013284118