“If temperatures drop in 2025, that does not mean that we no longer have to worry,” argues climatologist Robert Vautard

For the past year, the average temperature recorded across the planet has broken a new heat record every month. The month of May which has just passed confirmed this, announced the European Copernicus Observatory on Wednesday June 5. This surge in temperatures, initiated in spring 2023, has notably resulted in long heatwaves, brutal floods and devastating fires across the world. Franceinfo asked climatologist Robert Vautard, co-chair of the working group on climate physics within the IPCC, to take stock of this extraordinary climatic year.

Franceinfo: Each month has broken its own heat record for a year. How can we explain this headwind in global average temperatures?

Robert Vautard: Several factors come into play. The first, of course, is global warming which continues its course. There is also the influence of the El Niño phenomenon, which has been acting in the Pacific Ocean since spring 2023 and has started to decline after peaking in December-January.

This year, the particularity is that we are also observing extremely high temperatures on the surface of the Atlantic Ocean and the Indian Ocean, the cause of which we do not yet know how to truly determine. There is certainly a part of climate change, but also a part of natural variability, or even other forcing effects which would be added.

For example, we are seeking to understand the impact of legislation that recently came into force to limit sulfur emissions from ships on ocean surface temperatures. Some studies estimate that this influence is less important than previously thought, but several hypotheses are being studied.

Can records still fall in the following months? Can we anticipate when this series will end?

If we look at the temperature curve, we see that they continue to increase, in particular due to the seasonal cycle. But the warm anomalies will be less important as El Niño weakens. We can reasonably think that the temperature curve will cross that of last year by the end of the year.

From a physical point of view, a climate system cannot spiral infinitely in one direction in the space of a few years. On the other hand, we must monitor how this system evolves and what these evolutions tell us about a transformation that takes place over the long term.

“Having had an exceptional year in 2023, the warmest on record, may create some confusion and give the impression that there would be a sudden acceleration in the rate at which the planet is warming.”

Robert Vautard, climatologist

at franceinfo

In reality, such “spikes” appear in all climate models. We also experienced similar phenomena in the 1970s. However, the “jump” between the temperatures of 2022 and 2023 was very significant, which nevertheless makes it a fairly rare event. If such a jump were to occur again between 2023 and 2024, for example, then we would be in something that we do not know how to explain. But this is not at all what is expected.

However, should the speed at which global warming is progressing worry us?

We didn’t have to wait until 2024 to worry. Yes, we must continue to worry, because global warming continues at a significant speed, regardless of the variations linked to the alternation between El Niño [qui s’accompagne traditionnellement d’une hausse globale des températures] and La Nina [qui a tendance à rafraîchir]. El Niño years are warmer than in the past, La Niña years are warmer than in the past… Assuming that temperatures drop, in 2025 for example, which is entirely possible, that does not mean that There is no longer any reason to worry.

“Climate change acts on much longer time scales, of the order of decades and more. And today, we are already seeing that its effects are happening very quickly. It is manifested in particular by extremes everywhere in the world.”

Robert Vautard, climatologist

at franceinfo

This winter we saw extreme conditions in Asia, Africa and South America, with values ​​that exceeded the heat that a human is capable of absorbing, in particular because of humidity. In Asia, we saw it in 2022, 2023, 2024… Almost every year now, we observe extreme temperatures in spring, from March-April and before the monsoon, where humidity plays a very important. These phenomena are attributed to climate change.

France and other countries in the west of the European continent experienced a wet, even very rainy, spring. These conditions clash with the idea of ​​a warming climate…

In the territory, climate change has two faces: that of heat, with extreme episodes, or when the weather is bad, it takes the form of extreme rain. Climate change is very visible here and not only in the form of heatwaves and droughts. We see these effects almost every year. Just look at the number of floods that mainland France has experienced this year: just since the start of winter, between Pas-de-Calais, Charente, Moselle… Many territories have suffered severely. the effects of climate change.

Considering this year’s records, are certain already weakened ecosystems, such as glaciers or certain forests, at risk of crossing a “tipping point”, i.e. a stage beyond which it is impossible to go back?

Crossing a tipping point is observed over the long term. Some disappearances have already been recorded, such as that of small glaciers in France. If temperatures do not stabilize, the risk of reaching a breaking point increases. Currently, large masses of ice are turning to water in Antarctica, with glaciers and polar ice caps heavily destabilized by rising temperatures. There are still many unknowns, but if the planet’s glaciers reach their breaking point, it is estimated that sea levels could rise by 2 m by the end of the century, compared to an estimated rise of between 50 cm and one meter without breakage.

There is also the issue of the observed decline in general ocean circulation. On this point, the uncertainties are enormous and no one is able to say whether it can accelerate and reach a breaking point by the end of the century.

“What we do know is that climate change itself, with the global temperatures it is already causing, constitutes in itself a point of no return.”

Robert Vautard, climatologist

at franceinfo

Carbon dioxide, CO2, accumulates in the atmosphere. Even if we stopped all greenhouse gas emissions, it would remain there, in the atmosphere, for hundreds of years during which we would maintain the temperatures we know today. So the point of no return, in a way, is crossed each time the planet takes an additional fraction of a degree.

Can reducing greenhouse gas emissions stop global warming quickly enough, given what we have already observed over the last twelve months?

Drastically reducing greenhouse gas emissions is the only way to contain warming to a level such that the consequences remain manageable by society. We must quickly reduce emissions, with a goal of carbon neutrality in 2050. Even if it seems difficult to establish or implement today, we must do everything to get closer. What we have seen in recent months across the world is not an example of what could happen in the future, it is what is already happening with today’s conditions. . Without reducing emissions, tomorrow’s extremes will be worse. Not at the end of the century, but in ten years.