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Current heat almost impossible without climate change: study

July 25, 2023

The hot spells in parts of Europe and the US would not have occurred without human-made global warming, researchers say. This month is likely the hottest the Earth has seen in about 120,000 years, according to some.

People walk next a mist machine to cool down, in Monastiraki district of Athens, on Thursday, July 20
Temperatures in Southern Europe, as here in Athens, have been rising well over 40 C (104 F)Image: Petros Giannakouris/AP Photo/picture alliance

Human-made climate change appears to be overwhelmingly to blame for intense heat waves affecting several world regions this month, a study released on Tuesday said.

In a rapid analysis of the current high temperatures, particularly in Southern Europe and the US Southwest, researchers from the World Weather Attribution group concluded that the deadly heat would have been virtually impossible without the continuing buildup of warming gases in the air.

So far, the world has warmed 1.2 degrees Celsius (2.2 degrees Fahrenheit) above pre-industrial levels, and scientists have warned that going beyond a 1.5 C rise will have catastrophic consequences for human civilization.

What did the researchers say?

Because of the warming climate, severe heat waves like the current ones can now be expected approximately once every 15 years in North America, every 10 years in Southern Europe and every five years in China, the researchers said.

If the global temperature rises by 2 C (3.6 F) above pre-industrial levels, as could be the case if humans fail to rein in greenhouse gas emissions, they will occur every two to five years by around 2050, they said. 

The heat waves have also been hotter than they would have been without climate change, according to the study.

Climate change has made the heat wave in Southern Europe 2.5 C hotter, the one in the US and Mexico 3.6 C hotter and the one in China 1 C hotter, the study said.  

Only the heat wave in China could have statistically occurred without global warming, the data used in the study showed, but was still made 50 times more likely by climate change.

How much heat can humans tolerate?

'Overwhelming' role of climate change

"The role of climate change is absolutely overwhelming," said climate scientist Friederike Otto of the Grantham Institute for Climate Change and the Environment at Imperial College London.

"As long as we keep burning fossil fuels we will see more and more of these extremes," she added.

"The most important thing is that they [heat waves] kill people and they particularly kill and hurt and destroy lives and livelihoods of those most vulnerable," Otto said.

Among other things, the current heat has driven devastating wildfires in Greece that have caused mass evacuations in some areas.

The researchers used weather data and computer model simulations to compare the climate today with that of the past to see how far the current heat waves diverge from what would have been expected without global warming. 

Although the results have not yet been peer-reviewed, the techniques used in the study are considered scientifically valid.

tj/fb (AFP, AP)