Climate: why current mild weather is a ‘ticking time bomb’

Flowering tree in Rennes, January 6, 2023 (©Timothée L’Angevin /

If some like it moderate temperatures From the end of 2022 and the beginning of 2023, after the cold in early December, we should not be too happy about this. Quite the opposite.

However 2022 was the hottest year ever recorded in France According to Météo France, the end of the year was marked by exceptional mildness and temperature records broken in late December and early January, the current context should indeed be cause for concern.

“False Spring”

“It’s normal for the mildness to peak in winter, but above all, this the length of the problematic period”finds Serj Zaka, agroclimatologist at ITK and administrator of the Infoclimat association.

In some winters it can be +10°C and this is not a problem. On the other hand, what is new this year is that these peaks of sweetness go up to +20°C and last longer, sometimes for whole months. This is what is happening right now.

Serge ZakAgroclimatologist

The expert, who predicts that there will be a “hidden sweetness between +3 and +5°C above the norm” for a few more days until January 15, does not hesitate to talk about it. “Time Bomb” encountered what he called a “false spring.”

The result: the species wakes up

This long period of mildness causes the awakening of some plants that have already started their first bloom…in January! According to the agrometeorologist, “all species have two to three weeks in advance”, some more.

For the awakening of plants, some use the length of the day (shorter in winter), while others determine depending on the duration of the cold period during winter. When it is long enough, it can start at the beginning of spring.

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We didn’t have enough cold for most plants to wake up. It’s the mild temperature that’s waking them up now. Although the day is short, they still react because they have a long sweetness.

Serge ZakAgroclimatologist

Which species are particularly affected?

Mostly waking up right now decorative trees in gardens, the agroclimatologist notes.

For hazel trees or, for example, mimosas, which usually bloom in mid-January, depending on the region, they started in late December, early January. About two weeks early.

Serge ZakAgroclimatologist

As for the first cherry, apricot or almond trees that “break” (open their buds), “we are still in the swollen bud stage. They have started to wake up, but it hasn’t opened yet.”

Why is this problematic?

The main risk of early flowering: arrival of frost can destroy already flowering plants. “Currently, at the level of agriculture (a sector that can cause large economic losses, editor’s note.), we have excessive development plants, but we have not yet reached the fateful threshold for agriculture”, notes Serge Zaka.

This “lethal threshold” is when the buds begin to open, because then “plants are exposed to the air and are therefore more susceptible to frost than when they are warm in bud.”

The agroclimatologist recalls the frost episodes of previous years, which in 2021 caused losses of more than four billion euros for viticulture and horticulture.

“We still have the risk of three months of frost and if that happens, destroys the blooming flowers”, he continues. How destructive it can be for buds:

Plants with swollen buds are more sensitive to cold, simply because there is sap inside, and if that sap freezes, it causes the bud to swell and the tissues inside the bud to burst.

Serge ZakAgroclimatologist

“We are not immune to the great cold”

Given the weather forecast, if the sweetness persists (enough to further develop the plants in the wake), temperature drop according to meteorologists, it should start after January 15.

“If temperatures return to seasonality, this will stop the plant from growing and this will prevent the early opening of the buds”, emphasizes Serge Zaka.

Right now, we can’t yet cry for a national agricultural disaster, but we’re not immune to a big cold snap in February.

Serge ZakAgroclimatologist

Not only plants are interested

Another problem is that plants are not the only ones that wake up early. “They told me about sun-tanned lizards, even coming out of hibernation As for the turtles, these species may not have enough food to eat at this time of the year,” the expert warns.

He cares for these animals “above and beyond other animal cycles.” If the frost returns, he warns, “These animals are in danger of dying. »

The same applies to birds, some of them are already “singing morning and evening as in spring.” If a big cold comes suddenly, we can face loss. »

We can clearly see that there is a deregulation of biological cycles, which is never a good point for the survival of ecosystems.

Serge Zak

A lack of high-altitude snow and ice also poses a problem for water resources “important for agriculture, humans and ecosystems, which are gradually released by spring melt.” .

Is this an isolated phenomenon or a major trend?

Of course, ecosystems are like that can adapt. “They have room for maneuver, a range of resistance temperatures inherent to them,” detailed the professional, noting that this range is crossed “regularly” and “more often.”

Previously, we left this row exclusively during climatic disasters. Now we have heat waves, droughts, late frosts, every year. Ecosystems are getting weaker every year.

Serge Zak

Growing “climate pressure”

This constitutes a recurring climate threat “Increasing climate pressure”putting ecosystems in a state of “suffering, thermal, water stress…”

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Plant populations may suffer more and more, animal populations may decline, and after a while this may lead to the extinction of species in certain regions or the extinction of an ecosystem.

Serge Zak

Although the agroclimatologist qualifies by reminding that a disappearing ecosystem will be “replaced by another that is more adapted to the climate,” the fact remains that the “transition period” is subtle, especially since “climate change is so rapid compared to climate change. evolution of ecosystems”.

However, “it’s been 30 years since INRAE ​​scientists published their reports stating that there is a greater risk of frost damage with climate change because plants are more developed in winter,” he notes. We can’t say we weren’t warned. »

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