Longer and more frequent heatwaves, exploding demand for air conditioning and even more threatening viruses: major cities around the world and their billions of inhabitants will face serious crises if the climate change on the planet continue at this rate and the temperature rise by 3 °C compared to pre-industrial times, warns report.

“The difference between 1.5°C and 3°C is a matter of life and death for billions of people around the world,” said Roger van den Berg of the US institute WRI, which published this report documenting the problems that the inhabitants of Dakar in Senegal, Rio in Brazil or Padang in Indonesia will face.

The report examines potential climate risks in nearly 1,000 major cities that are currently home to 2.1 billion people, 26% of the world’s population and more than 50% of those living in urban centers.

The report’s authors explain the big difference a 1.5°C rise in global temperatures compared to pre-industrial times will make to humans, compared to the 3°C rise the world is currently heading towards.

According to the most recent UN figures from November, the planet appears to be on track for a 2.9°C rise in temperature, based on the commitments made by nations so far.

“With 3°C warming, many cities could face month-long heatwaves, an explosion in energy demand to power air conditioning, and a change in the risks associated with insect-borne diseases – often all at the same time,” the authors point out. .

“People living in low-income cities will be hardest hit,” they add.

The WRI estimates that the longest heat wave to affect residents of major cities will be 16.3 days if the temperature rises by 1.5°C, and 24.5 days if the temperature rises by 3°C. Furthermore, their frequency will increase from 4.9 heat waves per year to 6.4.

At the same time, due to the heatwaves, the demand for air conditioning and therefore for energy will also increase, while the heat will increase viruses transmitted by mosquitoes, such as dengue fever, zika and chikungunya.

Globally, the poorest countries, which have less means of adaptation, will be more exposed to the effects of rising temperatures. In a world where the temperature will be 3 degrees warmer, sub-Saharan Africa will be hit hardest by the increase in the frequency of heat waves and the spread of viruses.

As a result Freetown in Sierra Leone or Dhaka “may experience heatwaves lasting more than a month”, with an average of seven heatwave events per year.

“The time has come to prepare cities for a much warmer world by doing everything we can to drastically reduce emissions” of greenhouse gases, van den Bergh concludes.