Hard to ignore: global warming it will put our body and brain to the test. First, directly, from the increase in the number of deaths during episodes of extreme heat, mainly linked to dehydration, as in 2003 in France with the death of almost 15,000 people. “Heat-related mortality among people over 65 have increased by 167% compared to 1990″. underlines an alarming study of The Lancet.
Added to this, the heavy rainfall or other more extreme and more frequent weather events that cause numerous victims, such as as evidenced by the floods in Valencia in Spainwhose provisional balance is 227 deaths. But many other indirect effects significantly affect our health. Climate change will therefore significantly modify agricultural production, reducing yields in some cases. “We also observe a degradation of the nutrient composition of some cereals with heat”explains Basile Chaix, director of research at Inserm and the Sorbonne University.
therising temperatures it also promotes 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 appear in France. “Between January 1 and April 19, 2024, 1,679 cases of imported dengue were notified to Public Health France compared to 131 in the same period in 2023.” note Public Health France. An explosion for two phenomena: the heat increases both the number of eggs laid in female mosquitoes, but also promotes the replication of the virus. Another disease vector: the tick. The latter, present on most of France, sees its development cycle accelerate with the rising temperature.
The risk of suicide
Another concern that increasingly concerns researchers: the direct link between heat and the degradation 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 each increase of 1 ° C in the 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 amount of hate messages on the social network.
increase online hate by 22.5%. In question: the lack of sleepon 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 that certainly increases with the scarcity of resources, especially water, already the subject of many clashes in France.
Pollution and heat: a bad cocktail
It is customary to see the warning sign on the road during the summer holidays: “Air pollution, it reduces your speed.” And for good reason, the increase in temperature leads to
the increase in the concentration of ozone in the air, a gas very irritating to the human mucosa. Another effect of warming: the increase in the number and intensity of forest fires. In France, seven mega fires – those that destroy more than 100 hectares of forest – 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 years in 2050, and twenty if we follow the most pessimistic scenario of scientists. However, burning wood emits fine particles called PM 2.5 – whose diameter is less than or equal to 2.5 micrometers – which penetrate inside the lungs. In addition, dust storms in arid and semi-arid regions, which are also growing 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.
