Since the end of April, the precipitation has also rained down viral comments on social networks questioning global warming. “It’s raining everywhere all day even in the South […] Despite a very rainy month of March + April, the media dare to talk about drought and warming every day #crooks”, an Internet user on Twitter indignantly, accompanying his post with weather maps announcing rains.
Others use a rainy weather map and draw a parallel with the twenty departments put on drought alert. And denounce the fact that France would have “fallen on its head” as during the Covid. At the beginning of May, it was the cool temperatures “below seasonal averages” that would defeat so-called forecasts of “heat waves not seen for decades in May”. The accumulation of these posts aims to demonstrate the absence of reality of global warming.
FAKE OFF
Except that this is a confusion between weather and climate. Asked about this content, Jean Jouzel, paleoclimatologist and former vice-president of the Intergovernmental Panel on Climate Change (IPCC), said he had no problem saying that there was precipitation 30% higher than the averages in March or that temperatures may have been lower than seasonal averages in May.
“My fear is that if we have a perfectly normal summer, which is quite possible, people will say: you see global warming, that’s not true,” he says. No, global warming is the average temperature increasing, and that is very well documented”, with the first part of the IPCC assessment report, published in 2021. This is the latest update scientific knowledge on climate change, which highlights in particular that the global surface temperature “has increased more rapidly since 1970 than during any other 50-year period over the last 2,000 years”.
In France, the average temperature has increased by 1.7 degrees, including since the 1960s, he recalls, specifying that this means increasingly mild winters, earlier and later heat waves, more significant, heat records broken, but that there can still be harsh winters. And adds that not all summers will be like that of 2022. “Last summer was exceptional, he explains. We may not find a summer of this type again until 2030. They are becoming more and more frequent, but it is not every year. »
Trends over long periods
“What the climatologist is going to look at is that 2022 was the hottest year in France for a hundred and fifty years and not just that, it broke the record for the year 2020 by almost 1.5 degrees. , that’s the conclusion, he supports. Not the fact that there was a month in a place that was colder than average, that’s completely normal. »
This is also explained by Simon Mittelberger, climatologist at Météo-France. “There is a lot of confusion between the climate side and the meteorology side [dans ces posts], that is to say that the trends in terms of global warming are trends over long periods: on average, we are moving towards increasingly hot months of May, but without making it impossible to May have occasionally colder, more rainy months. »
May, a month of transition
Regarding precipitation in May, an excess of nearly 20% was noted [au 15 mai 2023], details the climatologist of Météo-France. This month contrasts with May 2022, which had been extremely dry, with a rainfall deficit of almost 65%. On the contrary, in 2021, a surplus of nearly 40% was noted. What to conclude? “Generally speaking, May is a month of transition between the winter and summer season, which means that we can have both months which can be very dry in certain years, but also very wet months”, completes- he.
This observation is also valid for temperatures. “In 2022, we had an exceptionally hot month of May, the hottest ever recorded on the scale of France, continues Simon Mittelberger. If we go back to 2021, May had been much colder than normal with a difference of -1.6 degrees. We can find the months of May above as well as below normal. »
Groundwater in the red despite the rains
Finally, despite the spring rains in France, 68% of the water tables remain at moderately low to very low levels, including 20% at very low levels, according to the hydrogeological bulletin of the Bureau of Geological and Mining Research (BRGM), published May 17.
In March and April, the cumulative precipitation was excessive over a large part of the territory. Some aquifers have been able to recharge, but after the winter drought, the situation remains heterogeneous and worrying, particularly on the Rhone corridor and around the Mediterranean.