signs of climate change in France? 19/03/2022

Climate change in France between now and 2100 – Badeau et al. 2007

Increasingly contrasting weather in France:

The winter of 2021-2022 will not be remembered as a very harsh or cold winter. Climatic events generally remained few in number, and it was, on the contrary, the anticyclonic periods that dominated and proved to be especially recurring for several months now.

No cold wave was observed either throughout the winter period and the snow was almost absent on the plaine, only concerning certain regions in the east and north. Ultimately, winter ranks 2021-2022 among the softest and driest in over 60 years nation-wide.

Comparison of precipitation and average winter temperatures in France since 1959 – Meteo France

It is especially in the Southeast that this winter was the driest with only ten days of rain in 3 months and precipitation deficits reach up 70 to 80% in many sectors. Snow was also almost absent up to high altitudes in the southern Alps due to the lack of rainfall and temperatures that remained too high.

This has been noticed for several years the winters are generally much milder than usual in the country with the winter of 2019-2020 on the first step on the podium (above + 2.8 ° C). A trend that has increasingly been asserted since the beginning of the 2010-2020 decade.

Average winter temperatures in France since 1900 and deviation from the 1981-2010 average – Meteo France

In terms of rainfall, this trend is more heterogeneous for the winter season, but we also noticet a significant contrast from month to month in our country. The weather can remain permanently dry and anticyclonic for several weeks or even several months in the country, however these periods are followed almost systematically by much more disturbing episodes over a short period of time. The year 2020 was a very good example of this type of situation with very dry months interrupted by much wetter periods.

Annual rainfall in France in 2020 – Weather cities

The most recent example was the markedly rainy episode involving the Languedoc and the Cévenn from 11 to 14 March 2022 with total volumes of over 200 to 400 mm in 48 hours, i.e. 2 times more than in the previous 3 monthswhich appears from the soil moisture index in Hérault from 1 December to 13 March with d.Values ​​close to record lows in early March and close to record highs a few days later.


Development of the soil moisture index in Hérault from 1 December 2021 to 13 March 2022 – Meteo France

It therefore seems that the climate is gradually being torn apart in our country increasingly contrasting seasonsalternating between very dry periods and periods suddenly very disturbed, sometimes extremely.

The same goes for temperatures. If the general trend is towards gradual warming, Abnormally hot periods are more and more frequent, regardless of the season. We remember the unusual heat waves of June and July 2019, the increasingly frequent early heat waves or even more recently the warmest holiday season ever observed in late 2021.

Map of sweetness registrations (non-exhaustive) from December 29, 2021 to January 1, 2022 Weather cities

The uprising in the Sahara is also an example that supports this gradual climate change in France. These are actually made more and more frequently and especially of more and more markedly over the years. If the episode in mid-March 2022 seems unusual, it should be remembered that a similar episode had been observed a year earlier in February 2021. These events mark the general tendency for the recurrence of strong south / south currents – west brings air directly up. from North Africa in all seasons.

Satellite image from February 6, 2021, showing the sand cloud stretching from Algeria to France – MODIS-TERRA

What trends for the future in France?

The climate therefore seems to be changing little by little in France and this trend has become more and more visible in recent years. What will the climate look like in the future in our country?

Temperatures:

Rising temperatures are the most well-known element in climate change. Average temperatures have been rising steadily for decades now in the world with an estimated value of + 0.9 ° C worldwide over the period 1901-2012 according to the IPCC.

In France, the increase is even greater + 1.7 ° C approximately from 1900 until today with a more marked acceleration since the 1980s. Over the period 1959-2009 we observe a trend of + 0.3 ° C on average per. decadee and an even more marked increase between spring and summer.

Deviation from the norm (1961-1990) of average temperatures since 1900 – Meteo France

This trend is expected to continue in the coming decades. Given a rather optimistic intermediate scenario leading to a reduction in greenhouse gas emissions, average temperatures should rise further by + 1.6 ° C nationally in 2050, + 3 ° C with a pessimistic scenario. The increase is even greater between now and 2100 according to these two scenarios.

Development of average temperatures according to two scenarios between now and 2100 in France – AFP

This would evoke days of frost and less and less frequent cold waves and on the contrary still early and marked heat waves. The current trend should therefore continue to triumph and even rise in the coming years, especially as the observations sometimes exceed the most pessimistic scenarios to date.

With this increase, the climate and biodiversity will change greatly in our country. The Mediterranean climate, which is very hot and dry in summer, is expected to gradually extend north and west to spread to Burgundy and Poitou as well as near the Pyrenees, and the climate in Aquitaine was to gradually encompass much of northern France.

Climate change in France between now and 2100 – Badeau et al. 2007

Rain:

In terms of precipitation, the current trend, which is very much the opposite, should continue to increase in the coming decades. In the period 1959-2009 we observe one increase in annual rainfall in the northern half, but a decrease in the southern half. In the spring and fall, precipitation is generally increasing on our territory, however summer and winter are much more opposite, more and more arid in the south.

According to the models, this very opposite trend was to be accentuated in the coming decades with a systematic increase in precipitation in winter, often greater than 10% and a fall in the hot season of -10 to -20%. If the winter rise could compensate for the summer deficit in the north, the situation could become more problematic in the south with a gradual drying up of the climate.

Development of annual and summer precipitation for the period 2071-2100 across Europe – eea.europa.edu

Increasingly frequent extreme events?

The trend of an increase in extreme events in France mentioned above has been observable since the middle of the 20th century. The number of hot days (maximum above 25 ° C) is increasing, while the number of freezing days is decreasing.

Heat waves are expected to become more frequent in the coming decades. Their frequency is already twice as high since the late 1980s than between the end of the 19th century and 1950. Their intensity is also increasing, with the four longest and four of the five most intense heat waves occurring after 1981.

Intensity and duration of heat waves in France since 1947 – Meteo France

The trend is also applicable at the level significant rainfall events and floods. If the quiet periods are more frequent, the intensity of the disturbed events after them seems to have increased in recent years, especially near the Mediterranean. In fact, there has been an increase in the frequency and intensity of these phenomena in these regions since 1961.

The intensity of extreme rainfall in the Mediterranean since 1961 – Meteo France

Although intense rainfall events are expected to be more frequent, they should be linked to the intended increase in the number of droughts and their extent. As previously mentioned, quiet periods should be more frequent, which at times induces marked risk of drought over many regions and therefore also a greater fire risk and extends to a larger part of the territory.

Development of the risk of fire in France between now and 2100 – Meteo France

Anyway, these drought periods could be interrupted with short, much more disturbing periods similar to what may have happened during the year 2021, when the spring had been very calm and dry with increasing drought in many regions, but the summer had proved to be unusually unstable with regular floods in the northeastern part of the country.

>> Overall, the future looks more and more opposite in France in terms of climate. If the warm trend stands out clearly with increasingly absent winters, lasting heat waves, ever earlier and more prolonged, the weather events are also expected to become more intense.

Persistent and increasingly widespread periods of drought alternating with more intense episodes of disturbance, contrasts from one region to another or even from one season to another, it will be the climatic and meteorological events that should characterize the coming decades.

According to observations of recent years, it seems that this trend has already taken hold in our country and should continue to rise.

Leave a Comment