A French climatologist's cry of alarm
A climatologist contacted us to share with the public the climate changes occurring in France. He observed a very rapid warming, particularly during a sensitive period for vegetation.
Vincent Cailliez, winner of the André Prud’homme Prize, awarded by the Société Météorologique de France (Weather and Climate), shares with us the conclusions of his work. For spring, real climate change is happening much faster than physical models suggest. The forecasts published by the IPCC in 2021 predicted a warming of 1.5°C in 55 years of the average maximum temperatures, between 1995 and 2050. In fact, the climate is changing much faster. In 35 years, spring days are already around three degrees warmer (2.5-3.8°C) in the Massif Central as well as in part of the Alps and the Pyrenees. This divergence is present across the whole of Western Europe, albeit less intense. The observed temperatures are therefore already much higher than the IPCC indications. Vincent Cailliez compares them to the warming forecasts under medium to high GHG emission scenarios (SSP4.5 to SSP7.0). For the first few decades, the differences between the trajectories of the two IPCC scenarios are quite small, and the reality exceeds them by far (see the graph in the short video below). This is an alarming information. We know that the climate of Western Europe is changing quickly, but the figures that appear here are even higher. I hope that these are only seasonal variations, limited to spring. It is also possible that it's particularly strong in hilly and mid-mountain areas.
This frenetic pace suggests more generally that certain extreme events predicted for the end of the century, floods and deadly heat waves, could occur much earlier.
Local ecosystems will also be disrupted much faster. Yet we need them for proper functioning of the biosphere.
Vincent Cailliez also adds that as we do not reduce CO2 emissions as much as the IPCC recommends, the continuation of this excessive warming is the most optimist scenario we can expect for the coming decades.
AP3C research and development project
The AP3C project was based on the actual warming observed in France, and more particularly in the Massif Central. It was launched in September 2015 to obtain localized information and to diagnose the small-scale effects of climate change. The team analyzed local temperatures since 1980. They then used the relative perspectives of global physical models and updated them with the actual trajectories. In short, they carried out a "slope correction", unprecedented in Europe at least.
They conclude that if the evolution continues at the current rate, it would lead to +4°C annual average at the end of the century as indicated in the TRACC reference trajectory which now applies in France.
Snow cover will be reduced in many places. Its disappearance will have a very strong effect on winter temperatures, the albedo effect will make them increase a lot, so the warming would be the strongest in winter in the impacted areas.
Rainfall will decrease in summer in the south of the Massif Central.
In spring, the water balance decreases a lot, to below -120 mm/50 years from the Cévennes to the south of the Lot. Change will appear most clearly in this season. In addition, the water tables would fill up less in winter.
Spring daytime temperatures are a crucial parameter for the restart of vegetation, and for agricultural production as a whole. Early droughts become more likely, and could pose serious problems for crops. The South-West is particularly threatened, by a combination of reduced precipitation and maximum increase in evaporative demand, but everywhere else the degradation is noticeable.
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Vegetation will start faster, especially at altitude, where it will advance up to one month in 50 years, in continuity with what is already happening.
The number of exceptionally hot days will increase rapidly in the south.
The conditions suitable for growing vines, including Provence rosé grape varieties, will move northward, but the south could be too hot for this crop as early as 2050.
Such a climate will prevail in France if the current rate of warming remains stable, and in this case we could certainly experience mild April evenings but we will already be exposed to heat waves, droughts and floods.
Tipping points and thresholds
Unfortunately, Vincent Cailliez also warns about the exceeding of tipping points (irreversible) and thresholds (theoretically reversibles). According to him, it is very likely that warming has already passed a threshold and therefore accelerated at the beginning of the 21st century.
He shows in particular the graph by James Hansen, which describes an acceleration observed since 2010 and predicts, at this rate, a temperature of +2°C in 2040 on average worldwide. Furthermore, ocean surface temperatures now seem to be increasing by 0.25°C per decade, which implies that warming would be close to the maximum suggested by James Hansen and shown by the yellow funnel on the graph below.
During the spring days, and for about forty years, inland France has been warming 3 to 4 times faster than predicted by the IPCC at medium altitude, and 2 to 3 times faster elsewhere. Vincent Cailliez suggests that these divergences will increase further in the future, because models don't include a series of tipping points that according to him we are crossing right now. He cites the Antarctic ice shelf, which is shrinking significantly, suggesting that a global tipping point is being reached. This vast expanse of ice reflects the sun's rays. Its melting will facilitate the absorption of heat by the ocean.
The concentration of atmospheric methane is also increasing faster and faster. This powerful greenhouse gas is emitted by industrial activities, by livestock, by rice paddies, by the permafrost of mountains and polar regions, as well as by the margins of the oceans.
On January 6, an editorial in Nature, a major scientific journal, also discussed the acceleration of the climate and a possible tipping point, the disappearance of clouds. It's a major concern for researchers in the field. The destabilization of these elements, of the Antarctic ice shelf, of methane emissions, and of cloud cover, would accelerate the change that would disrupt other elements of the Earth system, and so on in a vicious circle.
The fact that a climatologist is contacting us to share this information also shows us the gravity of the climate situation. Agriculture will be disrupted much more than expected, the population will be in danger, the future evolution is uncertain and very worrying. We must focus on safeguarding our living conditions on Earth as a priority.