The majority of world population could face deadly heat waves by 2100

Up to 75% of people could be exposed to extreme heat conditions

Up to 75% of people could be exposed to extreme heat conditions

Unless carbon emissions decrease rapidly, the three-quarters of world population could face deadly heat waves by the end of the century. This is the conclusion of a scientific study, which should be taken as a warning sign from governments and policy makers. Even if the world drastically reduces emissions though, still almost half the world’s population (48%) will eventually be exposed to extreme heat conditions. For the study’s author Camilo Mora from the University of Hawaii, it is still a human’s choice whether our future will be ‘bad or terrible’, as the impacts of warming could be reduced significantly. According to the study, published in the journal Nature Climate Change, the greatest risk to human life from heatwaves will be in the tropics, almost throughout the year, while in larger latitudes, this risk will be limited to the summers.

The method followed

The researchers conducted a global analysis of documented lethal heat events to identify the climatic conditions associated with human death and then quantified the current and projected occurrence of such deadly climatic conditions worldwide. They found 1,900 locations where, after 1980, climatic conditions had caused lethal heat events. Analyzing these conditions for the 783 most lethal heat events from 164 cities in 36 countries, they identified a global threshold beyond which daily mean surface air temperature and relative humidity become deadly.

Around 30% of the world’s population is currently exposed to climatic conditions exceeding this deadly threshold for at least 20 days a year. By 2100, this percentage is projected to increase to ∼48% under a scenario with drastic reductions of greenhouse gas emissions and ∼74% under a scenario of growing emissions. An increasing threat to human life from excess heat now seems almost inevitable, but will be greatly aggravated if greenhouse gases are not considerably reduced.

The research team created an online application which can, for any place on Earth, calculate the number of days in the year that temperature and humidity are estimated to exceed the lethal threshold. For example, by 2100, New York is expected to have about 50 days a year with climatic conditions above the threshold, Sydney 20, LA 30, but in Orlando Florida and Houston, Texas, all summer days will be above the threshold.

Examples of lethal heat events

The threat to human life from excess heat seems almost inevitable. In 1995, 700 people died in Chicago because of the extreme heat. In 2003, heat waves in Europe cost the life of more than 70,000 people, while in 2010, 10,000 deaths from the same cause were reported in Moscow. Cities like New York, Washington, Los Angeles, Toronto, London, Beijing, Tokyo, Sydney, Sao Paolo and others have faced deadly heat waves as well.

Source: National Geographic