Heat waves, water shortages, floods: how will France adapt to a 4°C warming in 2100?

The summer of 2022 with its 40 degrees and its exceptional drought marked the spirits. But if this was just a taste of the France of 2100, how could it adapt? The government kicks off its new strategy on Tuesday to deal with a warming that could reach 4 degrees.

“The global reality of global warming is essential (….) we must therefore prepare concretely for its inevitable effects on our territory and on our lives”, explains Sunday the Minister of Ecological Transition, Christophe Béchu, in a press release. .

“This is why we want to give our country a clear trajectory in terms of adaptation” in order to “build a model of resilience as close as possible to the realities on the ground and to avoid mal-adaptation.”

For this, it is launching a public consultation on Tuesday until the end of the summer to define the reference warming trajectory for the adaptation of France (TRACC), on which it will base the next French adaptation plan to change. (PNACC), expected for the end of the year, in parallel with efforts to reduce greenhouse gas emissions.

The first two versions of this plan, dating from 2011 and 2018, only took into account the hypothesis of the objectives of the Paris agreement, aimed at limiting global warming to below 2°C and preferably to 1 .5°C compared to the pre-industrial period, i.e. a maximum increase of +3°C for France. But is this still realistic, when France is already at 1.7°C?

The year 2022, the hottest ever recorded in France since 1900, with the hottest summer ever recorded in Europe, and recent extreme weather events around the world (drought in Spain, heat waves in Asia, hurricane in Burma, drought in the Horn of Africa …) show that the effects of climate change are accelerating.

The latest IPCC report estimated in March that global warming would reach the 1.5°C mark worldwide by 2030-2035.

– Up to two months of heat wave –

The government now wants to plan for a “more pessimistic scenario” corresponding to “the probable trend in the absence of additional measures”, in which global warming would be 3°C, and therefore 4°C in metropolitan France.

In this scenario, heat waves could last up to two months and certain particularly exposed areas (Mediterranean arc, Rhône corridor, Garonne valley) could experience up to 90 tropical nights per year.

The government expects more intense extreme rains, especially over a large northern half, and drought episodes lasting more than a month in the summer in the south and west.

Water shortages will multiply with “strong tensions on agriculture and forestry” and “almost all French glaciers will have disappeared”.

– 2.3 billion additional –

The increase in floods will have a “strong impact” on insurance, land use planning and transport.

Finally, “significant risks to all buildings, transport infrastructure and energy, water and telecommunications networks” are to be expected with “marked effects on coastal areas (erosion of the coastline, marine flooding )”.

At +3°C in the world, the drop in gross domestic product (GDP) would be between 6.5% and 13.1%, estimates the reinsurance giant Swiss Re. On the insurance side, the damage could increase by 30% by 2050. Agricultural crop losses of 7.4% for wheat and 9.5% for barley are expected in 2050, and for the forest, the yield would drop between 4.6% at 11, 6% for pine.

Faced with this, the French government, in addition to the measures already in place (Water plan, Green Fund, etc.), is proposing three projects.

The first will aim to update the various reference systems (Drias, Drias Eau, Climadiag) on ​​which the authorities rely to anticipate the effects of global warming. The second will be a support plan for local authorities while the third will launch vulnerability studies to adapt economic activity.

“The adaptation measures to be put in place today, whatever the adaptation trajectory set, represent at least an additional 2.3 billion euros per year”, already warns the government.