"Without human activity, these temperatures would have been impossible"

More than 50 degrees in Death Valley in the United States, a historical record of 45.3 ° C in Catalonia, more than 43 ° C in Phoenix for 24 days: without climate change, such heat waves would have been "almost impossible" in Europe and the United States, said Tuesday the World Weather Attribution (WWA) network. Initiative scientists collaborated to assess the extent to which human-induced climate change has altered the likelihood and intensity of July extreme heat in these three regions.

July 11, 2021 in Death Valley National Park, California. AP - John Locher

Text by: Clea Broadhurst Follow


Read more

The main conclusions of this study are clear: the extreme temperatures we observe around the world would never have happened without human-induced climate change. "We've seen a lot of people in the media ask, 'Is this our new normal?'" says Dr. Clair Barnes, a research fellow in climate data analysis and interpretation for extreme weather events at WWA.

«If we continue to burn fossil fuels, we continue to emit CO2 and other greenhouse gases, the climate will continue to warm. It may be that one day we will look back and tell ourselves that it was a cool summer in 2023. And indeed, these events will become more and more frequent. »

According to the researcher, this type of extreme temperature would have been "totally impossible" in pre-industrial times. And action should be taken now to slow down the inevitable. "The temperature distribution has essentially shifted, so the type of average temperatures we would have seen in pre-industrial times would have been two and a half degrees colder in southern Europe," she continues. "The temperatures we see are abnormally warm, even in the current climate. The temperature evolution and conclusions are fully in line with the IPCC's warnings.


Alarming figures

A maximum heat of 53.3°C in the United States, such as that of July 2023, would have been virtually impossible to achieve in the region, if humans had not warmed the planet by burning fossil fuels. WWA scientists found that the defined heat waves are between 1 and 2.5° warmer depending on the region.

In line with forecasts from previous climate projections and IPCC reports, these events are no longer rare today: an event like the one currently occurring is expected approximately once every 15 years in the US/Mexico region, once every 10 years in southern Europe and once every 5 years in China.


This is always the problem with communicating the temperature increase, because it doesn't seem like much, 1°C. Clair Barnes explains. "But all of our agriculture, all of our infrastructure is designed to exist in today's climate. And if we continue to push the boundaries of what our current climate can do, we will begin to run up against the limits of our previously installed system of life.


Another study recently showed that we should expect a 30% increase in the number of days we will need air conditioning to make the climate livable in Northern Europe.

Increasingly phenomenal impacts

The WWA, a group of international scientists assessing the role of climate change in extreme weather events, spent a week analyzing the dangerous heat waves that swept across the northern hemisphere in July, destroying crops and livestock, starting wildfires, exacerbating water stress and killing people on three continents.

In China, this is an event that, pre-industrial era, should have happened about once every 250 years. Now, these extreme heat events are expected to occur every two to five years in the country. "We already see in the news how much of an impact this heat is. There are forest fires in Greece, but also in Canada, around the world. These types of events are more likely to spread and spiral out of control because temperatures are very high, causing fuels to dry out.


More than 60,000 people have died in recent years, including immediate cases of people dying from heat stress in Greece and Italy because they worked in the sun. "There are a whole series of consequences that will have immediate impacts on human health. And there are longer-term risks from these droughts potentially occurring in poorer regions and leading to food insecurity.


The authors of the report consider it "absolutely essential" to adopt international legislation on the phase-out of fossils at the 28th United Nations climate conference in Dubai in November.

NewsletterReceive all the international news directly in your mailbox

I subscribe

Follow all the international news by downloading the RFI application


Read on on the same topics:

  • Climate change
  • Climate
  • Our selection