The fingerprints of climate change on ever hotter heat waves


The fingerprints of climate change on ever hotter heat waves

PARIS (AFP) – Warmer, longer, more frequent. Heat waves like the one currently ravaging much of Europe, or the record-breaking heat wave experienced by India and Pakistan in March, are an unmistakable sign of climate change, experts said on Monday.

– Humans to blame –

“Every heatwave we experience today has been made warmer and more frequent due to human-induced climate change,” said Friederike Otto, senior lecturer at Imperial College London’s Grantham Institute for Climate Change. .

“It’s pure physics, we know how greenhouse gas molecules behave, we know there are more of them in the atmosphere, the atmosphere is getting warmer and that means we expect see more frequent heat waves and hotter heat waves.”

In recent years, advances in the discipline known as attribution science have allowed climatologists to calculate how much global warming contributes to individual extreme weather events.

The Indo-Pakistani heat wave, for example, would have been 30 times more likely with the warming of more than 1.1 degrees Celsius that human activity has caused since the mid-19th century.

The record-breaking heat wave across North America in June 2021, killing hundreds as temperatures soared to 50°C in places, would have been virtually impossible without global warming.

And the last major European heat wave, in 2019, was made 3C warmer by climate change.

“The increase in frequency, duration and intensity of these events over the past decades is clearly linked to observed global warming and can be attributed to human activity,” the Organization said on Monday. world weather forecast in a press release.

– The worst to come –

Despite the unbearable temperatures this week, scientists are unanimous: the worst is yet to come.

At 1.5°C of warming – the most ambitious target of the Paris climate accord – UN climatologists calculate that heat waves will be more than four times more likely than the pre-industrial baseline.

At 2°C or warming, this figure is 5.6 times more likely, and at 4°C, heat waves will be almost 10 times more likely to occur.

Despite three decades of UN-led negotiations, countries’ climate plans currently put the Earth on track to warm to a “catastrophic” level of 2.7C, according to the UN.

Matthieu Sorel, climatologist at Météo-France, said climate change was already influencing the frequency and severity of heat waves.

“We are on the way to increasingly hotter summers, where 35C is becoming the norm and 40C will be hit regularly,” he said.

– Danger of death –

Future heat waves largely depend on how quickly the global economy can decarbonize.

The United Nations Climate Science Panel has calculated that 14% of humanity will be hit by dangerous heat every five years on average with a warming of 1.5°C, compared to 37% at 2°C.

“In every place in the world where we have data, there is an increased risk of mortality when we are exposed to high temperatures,” said Eunice Lo, climatologist at the Cabot Institute for the Environment of the United States. University of Bristol.

It’s not just the most vulnerable people who are at risk of health impacts, it’s even fit and healthy people who will be at risk.”

There is a real risk in the future of so-called “wet bulb” temperatures – where heat combines with humidity to create conditions where the human body cannot cool itself through sweat – reaching deadly levels in many many parts of the world.

In addition to the imminent threat to human health, heat waves are worsening drought and making larger areas vulnerable to wildfires, such as those currently raging in parts of France, Portugal, Spain , Greece and Morocco.

They also threaten the food supply.

India, the world’s second-largest wheat producer, opted to ban grain exports after a heatwave impacted harvests, worsening a shortage in some countries caused by Russia’s invasion of Ukraine, a key exporter.

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