I.2.2. Climate change projections in the world, in France and in Île-de-France

The evolution of various climate parameters in the context of climate change are described in the Green Paper of the Regional Plan for Climate Change (ÎdF 2010), included in other regional studies on adaptation to climate change.

As most of the studies on climate change in France, the Green Paper is based on climate simulations by Météo-France (Appendix 2b, ÎdF 2010), which, in their turn are based on three IPCC scenarios:

  • The B1 scenario, considered optimistic, implying a stabilization world population in 2050 and proactive policies to reduce GHG emissions horizon;
  • The A1B scenario, median scenario, which assumes rapid economic growth based on more balanced energy choices and more efficient technologies;
  • The A2 scenario, considered pessimistic, implying a high population growth, low economic development and increased GHG emissions. (Fig.8)

During the twenty-first century, all scenarios predict a rise in average air temperature globally. Estimates of the increase the average global temperature by 2100 is between 1.8 ° C – B1 scenario, and 4 ° C – A1F1 scenario. These scenarios represent medium temperature values, within a rather wide (+1.1 to +6.4 ° C) range (IPCC, 2007)

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Fig. 8 Mean surface temperature change (IPCC 2007)

 IPCC projects more hot summers, higher minimal temperatures, more heat waves, less cold waves, more draughts as very likely, which, according to the likelihood scale of IPCC, means from 90 to 100% certitude of the occurrence of the particular event.(IPCC 2010)

It is also very likely that heat waves will be more intense, more frequent and longer lasting in a future warmer climate, while cold episode

s are projected to decrease significantly. Almost everywhere, daily minimum temperatures are projected to increase faster than daily maximum temperatures, leading to a decrease in diurnal temperature range. Decreases in frost days are projected to occur almost everywhere in the middle and high latitudes, with a comparable increase in growing season length. (IPCC 2007)

According to the latest projections of France’s climate in 21 century and in line with the premise of global scenarios of IPCC [1],  in the period between 2021 – 2050 France will experience an increase in average temperatures between 0.6 and 1.3 ° C ( higher in the Southeast in summer), an increase in the number of days of heat waves in summer, particularly in areas of the South-East quarter (Ouzeau et al. 2014)

The accuracy of available data does not allow to have a precise information about the possible changes in climatic parameters on the territory of Plaine Commune, so the maps for Île-de-France will be used (Fig.9)

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Fig. 9. Evolution of average annual temperatures for three IPCC scenarios by 2080 (source: Green Paper of the Regional Plan for Climate, Regional Council of Ile-de-France, IdF 2010)

The table below (table 3) summarizes the expected effects of climate change on the scale of the Ile-de-France, for the main effects of climate parameters and the three IPCC scenarios considered in the Green Paper:

Table 3. Expected effects of climate change in Île-de-France. Source: ÎdF 2010

Climatic parameter Current situation 2030 2050 2080
         
Average annual temperatures 11,5°C (1951-2009). -A2: Increase of 1.1 ° C.-A1B: Increase of 1.4 ° C.

-B1: Increase of 1.2 ° C.

-A2: Increase of 1.9 ° C is more pronounced in summer (2.6 ° C in July).-A1B: Increase of 2 ° C, was more marked (2.8 ° C to July).

-B1: Same trend in 2030

-A2: Increase of 3.4 ° C is more pronounced in summer (5.5 ° C in July / August).-A1B: Increase of 2.9 ° C, especially in summer (4.7 ° C in July / August).

-B1: Increase of 1.9 ° C is more pronounced in summer (2.5 to 3 ° C in July / August).

Annual rainfall 630 mm / year (1951-2009) -A2: Down 4.2%, mainly in summer.-A1B: No significant decline.

-B1: No significant decline.

-A2: Down 6.7%, mainly in summer.-A1B: Down 4.4% greater in the summer.

-B1: No significant decline.

-A2: Down 13%, mostly in summer.-A1B: Down 14%, mostly in summer.

-B1: 7% decrease, mainly in summer.

Heat waves Less than 5 days / year heatwave alert (1951-2009).30-50 hot days per year (1971-2000). Heat alert: No significant increase. 

Warm up to 60 days per year.

A rise starts. 

Warm up to 70 days a year.

Up to 30 days / year (A2). 

80 (B1) and 100 (A2) hot days per year.

Droughts 19 days / year (1951-2009). 28-34 days / year depending on the scenario

Main expected changes in climatic parameters at the regional level by the end of the twenty-first century are:

– A steady increase throughout the century of annual average temperatures (1.9 to 3.4 ° C by 2080), particularly pronounced in summer (between +2.5 and + 5.5 ° C);

– A significant deficit of average annual rainfall (up 14%), again particularly pronounced in summer: the Green Paper stresses the possible occurrence of a dry period, which may extend from May to September;

– A net increase of exposure to drought (28 to 34 days per year in 2080 against 19 in the last half-century);

– A significant increase in exposure to heat waves, with the doubling of the number of hot days and a significant increase in the number of heatwave alert days per year. (ÎdF 2010)

[1] It’s important to note that all the scenarios and projections used in the thesis are coherent, meaning that they are based on the same socio-economic development scenarios yet on different territorial levels (in this case national and global)

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