the(Intergovernmental Panel on Climate Change) estimates that with an increase in the global temperature of the globe of 1.5°C by the end of the century compared to the pre-industrial level, the frequency of episodes of extreme will be multiplied by four! In the United States, the heat is already the phenomenon which kills the most for thirty years: from 1991 to 2020, the heat caused the direct death of 143 people per year on average, followed by the floods, then the the the , and finally cold and snow. In this country, the have more than doubled over the past 40 years.
A thermal index is used to assess the risk to the human body
To measure the degree of heat-related discomfort and health risk, scientists use two indices:(heat index) which combines the temperature of the environment and the relative humidity in the shade, but also the wet bulb (wet-bulb temperature), a less subjective and more precise index. the wet bulb characterizes the lowest temperature of an object or body that cools when moisture evaporates from it. This index quite simply measures the ability of our body to cool down thanks to the during hot and humid weather. The idea is then to define from which level our body can no longer cool itself: it is from this level that the becomes real.
Originally the wet bulb was measured with a simple thermometer wrapped in a wet cloth and exposed to the open air. The thermometer then recorded the temperature as the water evaporated from the laundry. Nowadays, this index is calculated from electronic equipment in weather stations that work with satellite data. Theuses instruments located in the like AIRS (Atmospheric Infrared Sounder) et ECOStress (ECOsystem Spaceborne Thermal Radiometer Experiment). The American organization is currently developing a new project, the SBG (Surface Biology and Geology mission) in order to obtain more accurate data on the moisture evaporation process.
Some parts of the world will be too hot to survive by 2050
Scientists consider that the index wet bulb the highest a human can withstand is 35°C for six hours. The recordings ofhave already noted wet bulbs above 35°C many times since 2005: in the subtropics of Pakistan and the Persian Gulf. For 40 years, the frequency of these wet bulbs extremely high has tripled. Most of the hot and humid regions of the planet have an index wet bulb which generally does not exceed 25 to 27°C.
NASA’s climate forecasting models are trying to determine the countries where the index wet bulb will soon be too high to survive. This will be the case for southern Asia, the Persian Gulf (Iran, Oman, Kuwait), and the countries bordering the Red Sea (Egypt, Saudi Arabia, Sudan, Ethiopia, Somalia, Yemen) from 2050. Eastern China, parts of South Asia and Brazil are also expected to regularly exceed an index wet bulb 35°C by 2070. NASA predicts the same fate for some US states in the midwest 50 years from now, like Arkansas, Missouri and Iowa. However, the researchers point out that the risk of death is present even with indices lower than that of 35°C. Duringin the northwestern United States and western Canada (estimated 1,400 dead), the wet bulb did not exceed 25°C. The index testifies to a health hazard as soon as it exceeds 12°C below the normal, with body temperature around 37°C.