The pollen season extends from the end of winter to autumn.
But the global warming would be at the origin of the increase of the duration and intensity of this season.
A number of smaller scale studies, usually conducted in greenhouses, had indicated strong links between temperature and pollen levels.
Our work highlights this link on a continental scale, and establishes an explicit correlation between pollen levels and climate change driven by human activities.
"Climate change is not something distant and future. Its consequences are already very visible." William Anderegg, lead author of the study
The study was conducted from 60 monitoring stations in North America between 1990 and 2018.
Conclusions: In the United States and Canada, the pollen season starts up to 20 days earlier and can last up to 8 days longer.
Allergies would also be also more intense: The concentration of pollens would be up by 20.9% over the period.
However, the authors of the study noted regional differences.
This could depend on:
- the precipitation rate,
- the number of days of frost
- and the concentration rate of carbon dioxide
Note: Climate change accounts for 50% of the lengthening of the allergy season but only 8% of the increase in pollen levels.
Pollen can cause asthma, allergies or respiratory problems.