This post comes from the newsletter “Human warmth”, broadcast every Tuesday at 12 p.m. Journalist Nabil Wakim, who moderates the event, speaks every week Human Heat Podcast, answers questions from Internet users about the climate challenge. Here you can register for free:

Before we answer the question of the week, a little extra promo for the book “Chaleur humaine”, published and available in all bookstores. I hope you find there the spirit of the podcast and some food for thought for the debate on the climate challenge.

The question of the week

“Hello and thank you for your podcast. I’m sorry to ask a somewhat personal question, but over the last few years I’ve had more and more allergies and I see that more and more people around me are allergic to pollen. Is climate change to blame? » Question asked by Manon at chaud humaine@lemonde.fr.

My answer : Yes, climate change is making allergies worse, this is a scientific fact that has been proven for many years. On the one hand, the increase in temperature leads to an extension of the pollen season and, on the other hand, to a high CO concentration₂ in the atmosphere increases pollen production. For more information, see this very well-crafted article with graphics by my colleague Raphaëlle Aubert.

1 – Why pollen is amplified

According to Inserm, pollen allergies affect around 30% of adults and 20% of young people in France. Three reasons explain the gradual worsening of pollen allergies due to climate change. First, pollen seasons are lengthening: temperatures are higher, allowing certain trees to bloom earlier, particularly hazelnut trees, alders and cypresses. This has two consequences: the painful phase for allergy sufferers gets longer every year and the number of those affected increases.

Another factor is important: our use of fossil fuels – oil, gas and coal – increases the concentration of carbon dioxide (CO).₂) in the air. This excessive occurrence of greenhouse gases is the cause of climate change, but also has another consequence: CO₂necessary for plant photosynthesis, significantly increases pollen production.

Finally, as shown in the published map In this article (you have to go down a bit), climate changes are allowing certain species to gradually migrate to areas that are not really affected by pollen allergies today.

You still have 50% of this article left to read. The rest is reserved for subscribers.