It’s hard to ignore: global warming will put our bodies and brains to the test. First, directly, by the increase in the number of deaths during episodes of extreme heat, mainly linked to dehydration, as was the case in 2003 in France with the death of nearly 15,000 people. “Heat-related mortality among people over 65 increased by 167% compared to 1990,” underlines an alarming study of The Lancet.
Added to this, heavy rainfall or other more extreme and more frequent climatic events which will cause numerous victims, as evidenced by the floods in Valencia in Spain, the provisional death toll of which stands at 227 deaths. But many other indirect effects will significantly affect our health. Climate change will therefore significantly modify agricultural production, reducing yields in certain cases. “We also observe a degradation of the nutrient composition of certain cereals with heat”explains Basile Chaix, research director at Inserm and Sorbonne University.
Bad weather: electricity networks on the front line
Increasing temperatures also favor the development of disease-carrying insects. This is the case of the tiger mosquito, now present as far as Normandy. Dengue, Zika, Chikungunya… These tropical diseases are appearing in France. “Between January 1 and April 19, 2024, 1,679 cases of imported dengue fever were notified to Public Health France compared to 131 over the same period in 2023,” note Public Health France. An explosion due to two phenomena: heat increases both the number of eggs in female mosquitoes, but also promotes the replication of the virus. Another disease vector: the tick. The latter, present over most of France, sees its development cycle accelerate with rising temperatures.
The risk of suicide
Another concern that increasingly concerns researchers: the direct link between heat and deterioration of mental health. Several studies show an increase in mental disorders, suicides and even attacks, and more generally violence, during heat peaks. For example, for every 1°C increase in average monthly temperature, the risk of suicide increases by 1.5%. Even more surprising, an American study drew a parallel between extreme temperatures and the quantity of hate messages on the social network
increase online hate by 22.5%. The cause: lack of sleep, on the one hand, which increases irritability and stress. An effect of heat, on the other hand, on the production of hormones such as dopamine and serotonin, affecting, again, anxiety and mood. A violence which will surely increase with the scarcity of resources, particularly water, already the subject of several clashes in France.
“What doesn’t change are the physical limits of the planet” (Marie-Claire Daveu, director of sustainable development at Kering)
Pollution and heat: a bad cocktail
It is customary to see the warning sign on the road to summer holidays: “Air pollution, reduce your speed”. And for good reason, rising temperatures lead to
the increase in the concentration of ozone in the air, a gas very irritating to human mucous membranes. Another effect of warming: the increase in the number and intensity of forest fires. In France, seven mega fires – those destroying more than 100 hectares of forests – were recorded on average between 2001 and 2020 according to the National Research Institute for Agriculture, Food and the Environment (INRAE). Global warming will favor an average of ten per year in 2050, and twenty if we follow scientists’ most pessimistic scenario. However, the combustion of wood emits fine particles called PM 2.5 – whose diameter is less than or equal to 2.5 micrometers – which penetrate into the interior of the lungs. In addition, dust storms in arid and semi-arid regions, which are also increasing under the effect of climate change, add particles to the air. In the short term, these lead to an increase in respiratory and cardiovascular diseases. The long-term effect is more uncertain, but some scientists fear an increase in the risk of cancer or even psychological disorders such as dementia.
