Climate change leading to earlier and earlier heatwaves, scientists say

Issued on: 18/06/2022 – 16:10

Although heatwaves now happen regularly, this one came as a surprise – a clear indication that the consequences of global warming are being felt earlier and earlier.

Forecasters and meteorologists describe France’s current heatwave as “remarkably early”. Heatwaves in France usually take place in July or August. A heatwave in June is unprecedented and worrying, with meteorologists pointing the finger at man-made global warming.

“With climate disruption, these events are occurring earlier and lasting until later in the year. They are also more intense than they were in the past,” said climatologist Aglaé Jezequel. “Today, this is the exception, but with the changing climate, we can already expect heatwaves to arrive earlier,” she said.

A taste of our future climate

Extreme weather will gradually become the norm if we remain passive in the face of climate change, scientists say.

“We are already experiencing the impacts from, and the increase in, heatwaves today, but it could become much worse in the future if we continue to emit greenhouse gases (GHGs),” Jezequel added.

Oil, gas and coal are the main culprits of global warming. World leaders adopted the historic Paris Agreement on December 21, 2015 at the COP21 summit, setting out longterm strategies for countries to meet their commitments to wean themselves off fossil fuels.

The landmark agreement aimed to limit global warming to 2° Celsius this century, and continue efforts to limit it further to 1.5° Celsius.

But last September, two months before the COP 26 summit in Glasgow, with the target seemingly out of reach, UN Secretary-General Antonio Guterres warned that the world was on a catastrophic path towards +2.7°C of warming.

The most obvious sign of global warming caused by greenhouse gas emissions is the increase in the number and intensity of heatwaves around the world. “We are experiencing a foretaste of our future climate. There is only one solution to prevent this from becoming the norm: reduce greenhouse gas emissions due to the burning of fossil fuels,” climatologist Christophe Cassou told France Inter.

According to Cassou, who co-authored the latest IPCC (Intergovernmental Panel on Climate Change) report, this reduction must be immediate, sustained over time and on a large scale. “It’s not in three years. It’s now, because it’s the accumulation of CO2 emissions that counts for the level of warming, for the level of risk, and for the level of occurrence of these heatwaves.”

Heatwaves lasting longer, becoming more frequent

France’s national meteorological service, Météo-France, defines a heatwave as a continuous increase in temperature for at least three days.

In France, the data clearly show the multiplication of these heatwaves. Of the 43 phenomena detected since 1947, nine took place before 1989, the rest between 1989 and 2020. According to Météo-France, there have been “three times more heatwaves in the last 30 years than in the previous 42 years”. 

“The country has warmed by 2°C since the beginning of the 20th century, which is therefore higher than the global average of 1.1°C,” said climatologist Françoise Vimeux.

The heatwaves in June come after a particularly hot and dry spring that has already caused soil drought in a large part of France, leading to fears for the harvest and creating favourable conditions for fires. “May was the hottest month on record,” Vimeux added.

This is just the beginning of extreme hot weather events, climatologists say. According to Cassou, the probability of a heatwave today is one in ten. “In 2030, it will be one in five and around 2050-2060, it will be one in two,” he said.

At the current rate, Météo-France predicts an average of 20 to 35 days of heatwaves per year at the end of the 21st century (compared to 3-4 days at the end of the 20th century).

Cassou says the duration of heatwaves determines their impact. “What we show in the IPCC report is that these heatwaves last for a longer period of time, the summer seasons are longer and will have greater impacts – including heat waves that start early – in so far as they entail risks for agricultural yields.”

But the economic cost of heatwaves is much more far-reaching. According to the French public health agency Santé Publique France, the health impact of heatwaves in France between 2015 and 2020 amounts to between 24 and 37 billion euros.