Flowers blooming in the spring, trees turning color in the fall … the changing seasons can be beautiful. But for many people, they come with a major downside: seasonal allergies.

And research shows that allergy season is getting worse.

“Warmer temperatures and higher CO₂ concentrations are really kind of super-charging pollen seasons,” says William Anderegg of the University of Utah.

Anderegg was part of a team that analyzed pollen trends over three decades across North America.

They found that pollen season now arrives on average about 20 days earlier than it used to and lasts more than a week longer.

They also found that overall, there’s about 20% more pollen in the air.

“In warmer temperatures and higher CO₂ atmospheres, plants tend to grow a little bigger. They tend to actually grow slightly bigger flowers, and then produce more pollen per individual flower,” Anderegg says.

And he says that for people with severe allergies or asthma, pollen can have significant respiratory health impacts.

“This is a crystal-clear example of how global warming is affecting our health dramatically,” he says. “It’s really here with us with every breath we take in the spring.”

Reporting credit: Sarah Kennedy/ChavoBart Digital Media