A France a little warmer, particularly in the east, where frosts are less frequentand or soils sometimes become drier. Here is the country drawn by the update of “climatic normals”, more often called seasonal normals, by Météo-France this Tuesday. The public body updates these standards, which allow “characterize the climate” over a given periodevery ten years, to align with the recommendations of the World Meteorological Organization.
The new reference period is from 1991 to 2020, so forecasters will refer to averages for this period to “analyze climatic events in real time”, explains the weather service.
A rising average annual temperature
The new average annual temperature normal in France is therefore almost 13°C, at 12.97°C. An increase of just over 0.4°C compared to the previous reference period, which ran from 1981 to 2010 (12.55°C). The average annual temperature was even lower, at 11.82°C, between 1961 and 1990, the period that the WMO recommends taking as a reference for communication on climate change.
Hot weather up, frost down
Is the spring and summer than the rise of the new normal annual temperature is the strongest. She is also slightly more marked on the continental east, in the Grand-Est and Bourgogne-Franche-Comté regions, and a little less in the coastal areas, in Brittany and Corsica.
Compared to the previous period, the number of hot dayswith a maximum temperature greater than or equal to 30°C, increases in particular in Nîmes (+8 days), Figari (+9 days) or Marignane (+10 days).
These changes in climate normals do not not in question the heat wave vigilance thresholds, who “are calculated in relation to bio-meteorological indices”, in collaboration with Public Health France and other agencies, explains Matthieu Sorel, climatologist at Météo-France to AFP.
The number of frost days, with a temperature below 0°C, is itself falling8 days in Troyes, Poitiers, Langres or Chambéry, and up to 10 days in Lyon.
Less rain in the Northeast, more winter rain in the Southeast
For its part, the average cumulative precipitation changes little (a range between 911 and 935 mm over the updates), except in the North-East where this average cumulative decreases more significantly. Conversely, in PACA and Corsica, average rainfall increases, particularly during the groundwater recharge period, which runs from September to March.
Météo-France further notes a more marked drying of the soil from the Massif Central to the Grand Est, especially summer and fall, but soils pmore humid in certain areas such as the west facade, except Poitou.
The heat “rises” to the North and changes the climate of the cities
The lesson of these updates, for Météo France, is that the climate of the cities changes as the heat “rises” to the north from the country. If we compare the normals of 1961-1990 with those of 1991-2020, we see that “the climate of Lille today was the climate of Rennes before, that the climate of Châteauroux today was the climate of Agen before”, explains Matthieu Sorel, climatologist at Météo France to franceinfo.
The climate of Lyon before is now the climate of Strasbourg – Matthieu Sorel, climatologist at Météo France
“So we see that we have this rise towards the north of the climate of the cities of the South which characterizes well, unfortunately, the evolution of climate change”, he explains. “Soon, we will be able to cultivate vines in Northern Europe, it will no longer be only the fruit of the regions of Southern Europe. The climate of Lyon before is now the climate of Strasbourg”, he illustrates.