snow. Will global warming sound the death knell for plains snowflakes?

They’re one of the few fights we’d like to see more often. Unfortunately, they are rarer now. In the coming decades, snowball fights will indeed have to face a few forced truces due to a climate that will make it increasingly difficult for snow crystals to form and fall at lower elevations as it warms. Explanations.

Also read: What will our winters be like in 2050?

Subzero temperatures from the ground to the clouds

The formation of snowflakes is subject to strict rules that require very precise air configuration.

“For snow to exist, we have to have subzero temperatures, and that’s throughout the atmospheric column.”Matthieu Sorel, climatologist at Météo France, recalls. “If we have negative temperatures at one level, positive temperatures at another level, and negative temperatures again near the ground, we will have freezing rain, not snow.”he says.

Therefore, all layers of the lower atmosphere must be below 0°C in order for water vapor to condense to form crystals in clouds around dust grains, increase in size, and then fall to the ground without melting.

But by definition, global warming implies that these conditions are less and less fulfilled.

It has already snowed less

Because its effect is more spectacular in summer, but it also has consequences in winter. “We face ever-rising temperatures and increasingly mild winters”remembers Matthieu Sorel, who clarified this “The 9 Coldest Decembers Recorded Before 1970.”

The result of this structural warming: the number of snow days in the plains has therefore already decreased dramatically. For example, Rouen (Seine-Maritime) saw an average of 19 days of snow per year between 1961 and 1990, and only 11 between 1991 and 2020. He went from 16th to 13th at Orly (Val-de-Marne).

Also read: For the first time in the coldest village of France, there was no frost in October

“What we’re seeing is a reduction in both the number of episodes, the amount of snow that falls, and the amount of snow that stays on the ground.”Matthieu Sorel summarizes.

A phenomenon that will accelerate

As the climate of mainland France is still expected to warm (the average temperature recorded in France in 2050 will be 1.7°C higher than that recorded between 1976 and 2005), “Episodes of snow on the Plains will become rarer over the years as global warming increases temperatures.”. This decline is currently poorly measured, but undeniable.

The same should be true for frost days that return less and less, without disappearing, including in highly exposed areas like the Northeast or Midwest.

See also: VIDEO. Global warming: here is the temperature forecast for 2050 in France

There is little snow in the mountains

The situation will be similar in the mountains, where the snow cover should clearly decrease in both volume and thickness in the medium term.

“The general trend is a marked decrease in snow cover”confirmed Météo France’s Agathe Drouin earlier in the month. “The middle mountains will be more affected as the rain-snow limit will increase in altitude”.

The number of days on which Mercantour will record 50 cm of snow at an altitude of 1,800 m will thus increase from 45 at the end of the 20th century.e to 24 in 2050. In Devolu, this total will drop from 73 to 43.

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