A new study of more than 13.000 cities around the globe has found that the number of days on which people are subjected to extreme heat and humidity has tripled since the 1980s.
The increase affects almost a quarter of the world’s population, according to its report published in Proceedings of the National Academy of Sciences.
Over the last couple of decades, over 100 million people have moved from the countryside to the cities where more than half of the world’s population now lives.
Scientists investigated maximum daily heat and humidity on more than 13.000 cities between 1983 and 2016.
A reading of 30 is the coarse equivalent of 106 degrees Fahrenheit on the so-called “real” heat index-the point at which even most healthy people have trouble working outdoors for long periods of time and those who are unhealthy may get extremely sick or even die.
The researchers then compared meteorological data to statistics about the population of each city during the same 33-year period.
The worst-hit town was Dhaka, the fast-growing capital of Bangladesh, where the peak heat level rose by 575 million days in the period studied.
In the United States, contamination in about 40 large cities has “rapidly,” risen, most notably in the Gulf Coast states of Texas, Louisiana, Mississippi, Alabama, and Florida.