A spring air floated during the holiday season. Records of softness were broken all over France, with for example 20.9 ° C recorded on December 29 in Nîmes, or 20.7 ° C listed on December 30 in Marseille-Marignane, two cities where the measurements have been recorded since 1922.
The climatologist Jean Jouzel believes with franceinfo that this is a sign of global warming. “When we talk about global warming, we are inclined to focus our eyes on summers, summer heatwaves and episodes of drought”, argues the former vice-president of the Intergovernmental Panel on Climate Change (IPCC). In the collective imagination, the link is less clearly established with the “exceptional winter sweets”. Yet, he assures, with climate change “winters are getting milder and milder”. Here are three graphics to better understand this exceptional episode, and put it in perspective.
Fewer cold waves
Frigid temperatures, snowfall … Cold spells are episodes “durable and extensive” during which “the national average temperature (drops) at least one day below a certain threshold (-2 ° C)”, describes Météo France on its website. According to the institute, there have been 46 cold waves since 1947 in France. More than half of them (24) were observed before 1970, which means that there have been more cold spells in 23 years than in the last 51 years.
“There is a rarefaction of cold waves”, comments to franceinfo Christine Berne, climatologist at Météo France. “The last big cold snap dates from the beginning of February 2012. In the meantime, there was a small spike of cold in February 2018. But since then, we have not experienced a cold snap”, she recalls. And this trend is expected to continue: “The number of days of cold spells or frost is decreasing in all scenarios [de réchauffement étudiés par le Giec]”, according to the latest climate projections from Météo France (PDF).
Temperature averages on the rise
What is the origin of the wave of softness in recent days in France? Robert Vautard, climatologist at the CNRS, explains to franceinfo that “the meteorological situation meant that, for several days, air masses coming from the tropical Atlantic did not mix with air masses higher up” in Europe. According to the specialist, “So we had arrivals of ‘pure’ tropical air, which came from a relatively warm ocean, and which did not cool off along the way.” And, according to him, climate change has made the situation worse, “providing a small supplement compared to the meteorological situation”, Who “would not have happened a few decades ago”.
In fact, the temperatures recorded in winter (December, January and February) deviate more and more regularly from the seasonal norm. The average temperature measured in winters for the past 30 years on 30 points in France (thermal indicator) is 5.43 ° C. Since 2014, each winter has exceeded this threshold. The average “used today is based on the temperatures recorded between 1981 and 2010. The new normal, between 1991 and 2020, is being calculated at the moment and we should observe a slight increase”, specifies Christine Berne.
Between Christmas and New Years, the sweetest week on record since 1947
This latest infographic shows the exceptional nature of the wave of mildness observed in France in recent weeks. Météo France has published an image showing, year by year, the national thermal indicator, on a national average between December 24 and December 31.
“This is the sweetest week between Christmas and New Years on record since 1947”, writes the weather agency, reporting that the indicator for this period of the year 2021 is at + 10.7 ° C compared to normal.
* Graphic update: national thermal indicator, on an average of 8 days. This is indeed the sweetest week between Christmas & New Years on record since 1947. pic.twitter.com/YYq6puWsyV
– Météo-France (@meteofrance) December 31, 2021
For Jean Jouzel, “exceptional weeks like the one between Christmas and New Years will be more and more frequent” in the future. In detail, to fully understand, he argues that there will be “variability”. This means that we may not experience such sweetness again at the same time. “for five or six years” but that, in the end, these temperatures will still be more frequent with a longer period.
If the mild temperatures between the two New Years Eve could have been appreciable to spend a moment with family or friends, Robert Vautard believes that it would be a mistake to watch this episode only from an urban point of view, with sunny terraces and banks. calling for picnic. “For agriculture, this is not necessarily positive. Nature needs cold in winter so as not to bud too early”, he recalls. There, due to human activity, “nature will have to adapt to rapid and brutal changes”. For him, this “extreme softness” is the “a sign of global disruption that will affect many systems and not just the life of the holiday season.”
As pleasant as they are, these exceptional temperatures are similar, according to Jean Jouzel, to “a reminder of the reality of climate change which reminds us of the urgency to act”.