How about playing scared each other? Chronicle of a disaster scenario.

Various studies carried out by researchers at Princeton University and MIT in the United States have highlighted results that resemble disaster film scenarios. But here, reality could well join and even overtake fiction.

The main actor is once again global warming . In the near future, it could make all life in the tropics impossible. The threatened territory is vast. It extends mainly from Central and South America, passing through central and part of southern Africa, northern Australia and part of Indonesia. Hundreds of millions of inhabitants are affected. If we do not accelerate measures to reduce global warming, the situation in these regions will have become such that no life will be possible. This is essentially what emerges from the various studies.

In a few years, it will be too hot and the humidity will have become unbearable. The study, published a few days ago in Science Advances   is based on new, more precise computer data that models future weather trends and future climate disruptions in regions at risk.

Why are these regions of the world particularly exposed?

Due to an index which is called "index temperature thermometer wet globe, its original name wet bulb globe temperature (WBGT)." This index measures both the temperature, humidity and solar radiation observed in a given region. It is the only index of temperature felt to take solar radiation into account, unlike the heat index .

The WBGT index was developed by the United States Marine Corps at Parris Island in 1956 to reduce the risk of heat stress injuries in new recruits and has been revised several times. It is used in industrial hygiene, but also by athletes and the military to determine levels of exposure to high temperatures.

Compared to the studies of our researchers, the index shows dramatic trends that climatologists had underestimated. The concern is not so much the rise in temperatures, which is obviously worrying in itself, as the rise in humidity that accompanies it. And in the regions affected by the forecast, humidity levels are high. The combination of the two becomes fatal once past a certain threshold. If it is too wet, the body can not cool s e evaporating sweat. However, in humid regions, the evaporation of sweat is slowed down. If the process were to stop, the body would risk overheating. Medicine has shown that no human can tolerate a humid temperature above 35 ° C, even with plenty of hydration. The most resistant people can continue to evolve outside until a humid temperature of 32 ° C, but the value of 35 ° C is considered as a theoretical limit of survival.

Work carried out by researchers at Columbia University shows “that between 1979 and 2017, a humid temperature of 30 ° C, until then considered rare, has already been reached about a thousand times! The 33 ° C that the researchers thought was out of reach was recorded 80 times. "

Before the end of this century, we may well see waves of unprecedented population displacement. People will flee from unbearable “damp heat” levels. Moreover, the populations of the Middle East and certain regions of Africa did not wait until the end of this century to start moving in order to face the increasing heat and drought.

A scientific journal reported that: “At a humid felt temperature of 75 ° C (35 ° C with a humidity level of 85%), the human body cannot be cooled naturally to survive more than a few hours. These climatic conditions are still rare. But smaller heat waves have already occurred. In 2015, a heat wave killed more than 3,500 people in India and Pakistan. The observed wet bulb temperature was then 50 ° C. A similar temperature had already been observed in Chicago in 1995. "

It would take colossal means to make the most vulnerable regions livable by building infrastructures to protect them from bodily hyperthermia. However, these climatic disasters will largely affect poor countries unable to protect themselves. Without counting the devastation on the cultures which represent most of the time their only means of subsistence.

A researcher participating in the study says: "If greenhouse gas emissions are not drastically and rapidly reduced, these deadly heat waves could affect many parts of the world in a few decades, with devastating effects on land fertile rivers of the Indus and Ganges, for example, which feed millions of people. Even more frightening, the study conducted by Eltahir tells us that without reductions in carbon emissions, these heat waves will affect 70% of the world's population by 2100.

Seen from Europe or the United States, Bangladesh seems far away. However, the results of the modeling have not forgotten us. The heatwave that France experienced in 2003, for example, could become a recurring phenomenon. Our summer temperatures could then regularly exceed 50 ° C in certain regions of the country. Scientists estimate that the new temperature records will be 6 to 13 ° C higher than current records.

So much additional data, if it were still needed, which shows that time is running out. It is, therefore, more than urgent that the signatory members of the Paris Agreement who will meet at the end of the year in Glasgow for the COP 26 implement all the means in place to ensure that the commitments are respected, this time. . The answer to greenhouse gas emissions is, in large part, political. If we do not want to fall victim to a dramatic ending worthy of a disaster movie, then we must do everything to contain global warming. Otherwise, beware of the point of no return.