Summer 2023 heatwaves “impossible” without climate change

Records boosted by climate change. According to a study by the NGO Climate Central, greenhouse gas emissions made the heat waves that hit the world in the summer of 2023 more likely. Between June and August, most continents were affected by heatwave episodes: Asia, Africa, Europe or even North America.

Over this period, almost half of the world’s population, or around 3.8 billion people, experienced at least 30 days of extreme heat made worse by climate change.

“Hardly anyone on the planet has escaped the influence of global warming in the past three months,” said Andrew Pershing, vice president of science for Climate Central.

“In each of the countries we analyzed, particularly in the southern hemisphere where it is the coldest time of the year, we observed temperatures that would have been difficult to reach, if not impossible, without the climate change caused. by man,” he added. “Pollution from carbon dioxide emissions is clearly responsible for this season’s record heat. »

The NGO relied on methods to determine the probability of a given daily temperature in each country, with or without current levels of carbon dioxide (CO2) pollution.

The same approach allowed scientists to measure the role of climate change in extreme weather phenomena, such as the conditions that allowed the outbreak of major fires in Quebec this year.

Climate Central has developed a Climate Change Index (CSI) ranging from -5 to 5, with levels above 0 indicating temperatures made more likely by warming. For example, Level 3 means that climate change has made the recorded temperature three times more likely.

From June to August, 48% of the world’s population therefore experienced 30 days of temperatures corresponding to at least CSI level 3, and 1.5 billion people experienced it every day, according to the NGO’s calculations.

The role of climate change has been three to four times stronger in the heat waves experienced by the least developed countries and small island nations than by the much wealthier G20 countries, according to Andrew Pershing. Some countries “bear greater responsibility for the climate change and pollution that fuels the heat we are all experiencing right now,” he said.