Frozen mimosa from leaves to buds, whitewashed roofs, and glistening roads, covered by a centimeter of ice.
Sometimes very aesthetic on the face, episodes of extreme cold like this week are also formidably dangerous, on the tails.
And after the heatwave, avalanches, thunderstorms, strong winds, floods, waves-submersion, snow, it is the turn of the ice to have been the cause of the placing in red vigilance of four departments (the Vendée , Deux-Sèvres, Indre and Vienne) this Thursday evening and Friday morning.
If the specialists in climatic conditions had already placed several departments on orange alert for these slip risks, this is the first time, since the creation of color vigilance in 2001, that Météo France has used red vigilance for ice.
This colored device, which signals an exceptional danger, was created after two devastating storms at the end of 1999.
Appearance of new alerts and climate change
And it is clear that Météo France's map of France is colored, from year to year, more and more red.
According to Météo France figures, an average of 7 red vigilances have been activated each year over the last decade.
Much more than the previous decade.
And this year 2021 does not seem to be deviating from the rule.
Including the snow and ice alert on Thursday evening, this is already the fourth time that at least one department has been placed in red.
And we are only in mid-February!
weather alert infographic
To find the reasons for this increase, we must first turn to the vigilance criteria.
Since 2011, Météo France has added two new phenomena to its alert panel: floods, directly linked to Vigicrues, and waves-submersion.
“We see that two-thirds of the alerts in a year are due to floods and rain floods, points out Michel Lambert, deputy director of the general forecast department of Météo France.
In addition, these phenomena are more visible in vigilance because they extend over several days.
"
But that's not all: the weather - and no doubt climate change - has something to do with it too.
“We must not forget that we have broken heat records in recent years.
But also that a heatwave is quickly several days of alert, ”continues the specialist.
"Météo France does not cry wolf through and through"
Thus, according to the annual reviews, on average, in 2020, each department will have been affected by five episodes of strong vigilance (orange or red).
It was eight in 2019 and ten in 2018, with two very hot summers across the country.
If we are interested in the reasons for this vigilance, we see that other phenomena (except floods and heat waves) come back regularly.
Météo France does it too much?
The public establishment defends itself against any abuse by alerting the populations and the authorities.
“We do not cry wolf through and through, otherwise we would lose credibility,” assures Michel Lambert, with supporting evidence.
READ ALSO>
Climate: floods, floods… why is it raining so much?
Morning essentials newsletter
A tour of the news to start the day
Subscribe to the newsletterAll newsletters
Each year, the organization is evaluated by a whole series of actors, including members of Civil Security, agents from the road departments and hydrologists.
They thus calculate a false alarm rate, that is to say levels of vigilance deemed unjustified a posteriori, because the risk would not have occurred, or in any case not in the anticipated proportions.
And this rate is estimated at 10% for the year 2020, one of the lowest results of the last five years.
Conversely, when significant consequences are observed in a department not placed in orange vigilance, Météo France sees its other assessment rate, called the non-detection rate, increase.
It was 1.4% in 2019.