France France France France

Climate change France

Climate of France

France has a mainly temperate climate. Northern and western France are mainly low-lying, but there are some high mountain regions with the Alps and Jura in the east and the Pyrenees in the south, as well as the Massif Central in central southern France. Consequently, there are considerable variations in climate (1).


The mountainous areas are the coldest regions of France. Northern and north-western France has a maritime climate with mild winters and warm summers. Central northern France has rather colder winters and slightly warmer summers, with Paris having a mean annual temperature of 13°C and a seasonal range of ±8°C. Bordeaux in the southwest has very similar temperature climatology to Paris. Lyon, towards the south-east, has a more continental climate with colder winters and a greater chance of frost and snow. The Mediterranean coast and the island of Corsica have a Mediterranean climate with hot summers and mild, sunny winters. The pleasant winter and spring weather is often interrupted, however, by cold and blustery weather brought by a northerly wind called the Mistral. Nice has an annual mean temperature of 16°C, with a seasonal range of ±7°C (1).

Most of France receives a moderate amount of precipitation throughout the year. The exception to this is the Mediterranean climate area which has dry summers as the track of eastward-moving Atlantic weather systems migrates away to the north (1).

Nice has average annual rainfall of 800 mm, which mostly falls in the autumn and winter, although occasional thunderstorms do occur in summer. Central areas have little seasonal variation in rainfall, although the mechanisms change with summer rainfall associated with convective thunderstorms and winter rainfall with frontal Atlantic disturbances. Lyon has an annual average rainfall of 840 mm and Paris 670 mm. Western France is more exposed to storms coming from the Atlantic, so has more seasonal variation with increased rainfall amounts in winter. Bordeaux has an annual average amount of 980 mm and Brest 1140 mm. The high mountain areas have heavier precipitation, much of it falling as snow in winter (1).

Air temperature changes in France until now

The global warming recorded in mainland France during the 20th century is about 30 % greater than the average warming throughout the globe. The average annual temperature has risen by 0.95 °C in mainland France, compared to 0.74 °C globally. These values are even higher for only the second half of the 20th century: increase of 1.1 to 1.5 °C over the period 1950-2000 (2), or 1.5 °C over the period 1959-2009 (12).


Over the period 1960-2009 there is a spatially consistent warming trend in summer over France and a clear trend to fewer cool nights and more warm nights, and also to fewer cool days and more hot days. The warming trend for summer is 0.35 °C per decade (5th to 95th percentile of slopes: 0.24 to 0.48 °C per decade) and for winter 0.20 °C per decade (5th to 95th percentile of slopes: -0.02 to 0.40 °C per decade) (1).

Recent research suggests that there is a similar air temperature trend in the Alps at low and very high altitudes over the last 100 years. Temperature profiles have been analyzed from boreholes drilled at three different sites between 4240 and 4300 m above sea level in the Mont Blanc area (French Alps). A mean warming rate of 0.14 °C/decade between 1900 and 2004 was found. This is similar to the observed regional low altitude trend in the north-western Alps, suggesting that air temperature trends are not altitude dependent (5).

In the central Pyrenees minimum and maximum annual temperature have increased over the period 1910-2013 by 0.06 ⁰C per decade and 0.11 ⁰C per decade, respectively (13). This increase was larger over the period 1970-2013:  0.23 and 0.57 ⁰C per decade for minimum and maximum annual temperature, respectively. In this latter period spring is the season that presents the greatest warming, with 0.4 ⁰C per decade for minimum temperature and 0.9 ⁰C per decade for maximum temperature (13). 

Heat wave changes in France until now

From observations over the period 1951−2009 eight heat waves were extracted for the Paris Basin, i.e. a mean frequency of about 1 in 7 years (a heat wave being defined as at least one day with daily minimum 18°C and maximum 34°C, minimum duration of 3 days with relatively high temperatures) (9).

Changes in temperature variability in France until now

 

Precipitation changes in France until now

Global warming in mainland France during the 20th century is accompanied with an increase in autumn and winter rainfall (between 5 and 35%) and a drop in summer rainfall (2). Extreme daily rainfall shows an increasing trend in southern France since about 1985, according to a dataset over the period 1958-2013 (20).

Extreme fall 2014 precipitation in the Cévennes mountains 

Fall thunderstorms along the northern Mediterranean coast can produce a few hundred millimeters of precipitation within one day (10). These phenomena are triggered by moist air advected from the warm Mediterranean Sea, hitting the mountain range with convection possibly amplified by colder continental air aloft. Such extremes occurred repeatedly during the fall of 2014, inducing floods and casualties in several places during the season. Extreme precipitation In the Cévennes mountain range reached more than 300mm in a day in the fall of 2014 and induced a record (since 1950) maximal intensity when averaged over an ensemble of rain gauges. In this area since the middle of the 20th century, maximum daily precipitation in fall has increased about 30% and the return period of events such as those found in 2014 is estimated to having been reduced by a factor of about three. At least part of these trends is due to warming (11). 

Model simulations show that the exceedance probability of a 1-in-100-year daily extreme precipitation event in autumn in the Cévennes mountain range in the historical climate has increased by a factor of 2.5 ± 0.8 under the current climate (19). 

Snow cover changes in France until now

 

Ice cover changes in France until now

 

Wind climate changes in France until now

 

Glacier changes until now

From 1850 to 1980 glaciers in the Alps lost approximately 30-40% of their area and one half of their mass. Since 1980 until 1995 another 10-20% of the remaining ice has been lost (15). Data on the longest and most continuous series for six glaciers in the European Alps (In Austria, Switzerland and France, over the period 1962-2013) show a clear and regionally consistent acceleration of mass loss over recent decades over the entire European Alps (14). 


First results from field measurements indicate that the extreme warm and dry weather conditions in summer 2003 caused an average loss in thickness of glaciers in the European Alps of about 3 meters water equivalent, nearly twice as much as during the previous record year of 1998 (1.6 m), and roughly five times more than the average loss of 0.65 m per year recorded during the exceptionally warm period 1980-2000. In 2003 alone, the total glacier volume loss in the Alps corresponds to 5-10% of the remaining ice volume (16).

Air temperature changes in France in the 21st century

Projected temperature increase over France by 2100 compared with 1960-1990 (A1B emission scenario)  is between 2.5°C and 3.5°C. Increases are lower in the north, and higher in southern regions (1). Other research results, based on projections for seven climate models, point at higher temperature increase: 1.7–2.7° in 2050 (A1B emissions scenario) and 2.2–4.2° in 2080 (A2 and A1B emissions scenarios), compared to the present day (1971–2000) (7).

Future cold spells in Western Europe are projected to become about 5°C warmer (and remain above freezing point), thus having a significant climatic impact. This conclusion is based on research in which a cold spell (CS) is defined as a non-interrupted sequence of days in which the 5-day average temperature falls below a threshold value Tcold (3).

Paris

Model calculations based on two emission scenarios (A1B and A2) project an increase of 2-meter air temperature for Paris between 1971–2006 and 2072–2098 of +2.0/2.4°C in winter and +3.5/5.0°C in summer for the minimum and maximum daily temperatures, respectively (4).


The number of cold days (minimum temperature ≤ −5°C) in Paris becomes negligible at the end of this century. In rural areas near Paris, it is projected to decrease from more than 6 cold days per year in present time to about 1 day per year at the end of the century. In the same way, the number of very cold days (minimum temperature ≤ −10°C) which is already very small in present time becomes 0 at the end of this century. The number of frost days (minimum temperature ≤ 0°C) is projected to decrease by 50–60% in comparison with present climate. Finally, the number of ice days (maximum temperature ≤ 0°C) is projected to decreases from 6 to 1–2 days per year (4).

The number of very hot days (maximum temperature ≥ 30°C) is projected to increase from 5 to 6 per year to 29 (42) very hot days per year in urban and rural areas, and 33 (47) very hot days per year in suburban areas at the end of this century according to A1B (A2) scenario. The number of very very hot days per year (maximum temperature ≥ 35°C) is projected to increase from near zero in present time to 8 (15) in urban areas, 10 (17) in suburban areas, and 9 (16) in rural areas at the end of this century according to A1B (A2) scenario (4).

The number of tropical nights per year is projected to increase at the end of this century from 6 tropical nights per year in present climate to 35 (50) for urban areas, from 2 to 23 (36) for suburban areas, and from 1 to 15 (26) for rural areas according to A1B (A2) scenario (4).

The warming trend is more marked in rural areas than in urbanized areas because of the drying of natural soils. Actually, the extremes in temperature are the most important in suburban areas where the effects of partial urbanization and soil dryness accumulate. On the one hand, the urban geometry is less dense than that of the city centre, which reduces the shadow effects and promotes warming of the air in the street-canyon. In addition, the dryness of natural soils severely limits evaporation, which tends to strengthen the sensible heat flux. Because of this, the temperature difference between urban and rural areas, and thus the urban heat island effect, is projected to decrease between 1971–2006 and 2072–2098 (4).

Heat wave changes in France in the 21st century

Maximum summer temperature 

Current record maximum summer temperature in France is about 42°C. Record maximum summer temperature that could be reached in France at the end of the 21st century has been quantified with a regional climate model for a high-end scenario of climate change (the so-called RCP8.5 scenario) (17). This was done for five well defined geographical regions: South-West France (SW), Eastern France (EA), Brittany (BR), Northern France (NO) and the Mediterranean region (ME). These regions characterize the typical spatial extent of record-breaking temperatures and heat waves in France. According to the results mean regional changes in maximum summer temperature by 2100 range from 4.4 °C in Northern France to 6.6 °C in the Mediterranean region. Individual locations within these five regions can experience even greater changes: 6.6 °C (Brittany), 7.7 °C (Northern France), 7.7 °C (Mediterranean region), 9.6 °C (South-West France), and 9.9 °C (Eastern France), respectively. In fact, the authors of this study concluded that by 2100 under this high-end scenario of climate change, the increase in summer temperature maxima in France may exhibit a range from 6 °C to almost 13 °C, relative to historical maxima.


In France, the change in summer maxima of daily maximum temperatures is thus expected to be twice as large as the change in mean summer temperature that has been estimated to be ∼6 °C under this high-end scenario (18). These projections for 2100 point at much warmer summers than the hottest summers so far: in France, the 2003 and 2015 summers are the warmest and second warmest on record, with summer mean temperatures (averaged over France) being +3.2 °C and +1.5 °C warmer than the average value for the period 1981-2010 (17).

These results indicate that record maximum value in France could easily exceed 50 °C by the end of the 21st century. These extreme temperatures are experienced in desert regions, however. In agreement with similar studies of observed present-day heat waves, the results show that the regions with the driest conditions before the heat wave experience large temperature anomalies and a higher number of record-breaking temperatures during the heat wave. These conditions may result from high evapotranspiration in spring and little precipitation in summer. The results also show that regional heat wave temperature anomalies can vary by several degrees due to different soil water conditions prior to the heat wave (17).  

Paris

The number of heat-wave warnings is projected to increase from less than 1 day of warning per year in present climate to 14 (26) in urban areas, 11 (22) in suburban areas, and 7 (17) days in rural areas at the end of this century according to model calculations based on the A1B (A2) scenario. The heat-wave warnings will be more numerous in urban areas than in suburban and rural areas (4).

From observations over the period 1951−2009 eight heat waves were extracted for the Paris Basin, i.e. a mean frequency of about 1 in 7 years (a heat wave being defined as at least one day with daily minimum 18°C and maximum 34°C, minimum duration of 3 days with relatively high temperatures). In addition, for the periods 1960−1989, 2020−2049 and 2070−2099, the numbers of heat waves were projected (using the aforementioned definition of a heat wave) based on (1) several (regional and global) climate models and the A1B emission scenario, and (2) one regional climate model and 3 emission scenarios (A2, A1B, B1). For the period 1960−1989 on average one heat wave in 10 years was calculated, for 2020−2049 1 heat wave every 2 years was projected, rising to at least 1, and up to 2, heat waves per year on average over 2070−2099. Heat wave duration also increased in time, with mean durations varying between 6 and 12 days over 2070−2099, and exceptional durations reaching 5 to 9 weeks (9).

Changes in temperature variability in France in the 21st century

 

Precipitation changes in France in the 21st century

Europe shows a strong contrast in projected precipitation changes, with large decreases in the south and large increases in the north. France falls towards the southern region with decreasing precipitation, with projected decreases of up to 20% in the southwest, but with smaller decreases of up to 5% further north. The position of the transition zone between increasing and decreasing precipitation over Europe is uncertain, however.


Research results, based on projections for seven climate models, point at +0.4 to −14 % change in annual precipitation in 2050 (A1B emissions scenario) and +4 to −24 % change in annual precipitation in 2080 (A2 and A1B emissions scenarios), compared to the present day (1971–2000) (7).

Recent modelling studies confirm conclusions from the IPCC report of 2007 (AR4) that heavy winter precipitation and flooding could increase with climate change for continental France, although these projections are based upon large-scale climate modelling experiments across the European domain. Due to France covering the transition zone between Northern Europe and Mediterranean Europe, extreme precipitation events over the north and south of the country may show differing responses to climate change. In the Alps the more relevant extreme events such as those with 10-year return period remain in summer and increase strongly in intensity (21).

Snow cover changes in France in the 21st century

Changes in mean winter snow water equivalent (SWE), the seasonal evolution of snow cover, and the duration of the continuous snow cover season in the European Alps have been assessed from an ensemble of regional climate model (RCM) experiments under the IPCC SRES A1B emission scenario. The assessment was carried out for the periods 2020–2049 and 2070–2099, compared with the control period 1971–2000. The strongest relative reduction in winter mean SWE was found below 1,500 m, amounting to 40–80 % by mid century relative to 1971–2000 and depending upon the model considered. At higher elevations the decrease of mean winter SWE is less pronounced but still a robust feature. For instance, at elevations of 2,000–2,500 m, SWE reductions amount to 10–60 % by mid century and to 30–80 % by the end of the century (6).

Based on a very large ensemble of high resolution climate projections it was suggested that large changes in snowfall over the French Alps are to be expected in the future climate, with a winter decrease of roughly 25% in the middle of the 21st century compared with 1961–1990 (with a 20–80% quantile range of 20-35% decrease) under the A1B emissions scenario (8).

Wind climate changes in France in the 21st century

 

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for France.

  1. UK Met Office (2011)
  2. ONERC (2007/2009)
  3. De Vries et al. (2012)
  4. Lemonsu et al. (2012)
  5. Gilbert and Vincent (2013)
  6. Steger et al. (2013)
  7. Habets et al. (2013)
  8. Piazza et al. (2014)
  9. Lemonsu et al. (2014)
  10. Ducrocq et al. (2014), in: Vautard et al. (2015)
  11. Vautard et al. (2015)
  12. Ribes et al. (2016)
  13. Pérez-Zanón et al. (2017)
  14. Vincent et al. (2017)
  15. Haeberli and Hoelzle (1995), in: Agrawala (2007)
  16. UNEP (2004)
  17. Bador et al. (2017)
  18. Terray and Boé (2013), in: Bador et al. (2017)
  19. Luu et al. (2018)
  20. Blanchet et al. (2018)
  21. Brönnimann et al. (2018)
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