“Climatically, we can say what this will look like, but it doesn’t really make sense. Today’s Paris is not livable at +4°C for example! explains Magali Reghezza-Zitt, geographer specializing in adaptation, member of the High Council for the Climate. The difficulty is that people’s lives will not depend solely on the climate, but on our capacity to have sufficiently transformed our ways of living. “Let us still try to paint a landscape. For the geographer, we must imagine winters where the cold becomes very rare but still exists and in which we will be “less and less well prepared, therefore which will generate a lot of mess “. Summers that start much earlier with the first heat waves in May and the last in October, where 40°C is the norm.
“In a climate of +4°C, summer 2022 is a cold summer “, she says. However, it is the second warmest recorded since 1900, after 2003. When it rains, the storms will be very violent and will dump a lot of water. It will snow much less, the glaciers will have disappeared, with as a result of the absence of spring melt feeding the rivers. “Water will be a rare resource everywhere in France “, she notes. Low-lying coastal areas will be flooded very frequently. “France will depend on this climatic atmosphere. But daily life will not be the same depending on whether we have succeeded in decarbonizing and adapting, or whether we have failed “, insists Magali Reghezza-Zitt.
In Lyon, precision plantations
What trees will grow in Lyon at the end of the century, when it is promised the climate of Rome? “We are even told about the climate of Algiers! But when it comes to vegetation, it is impossible to take a model: we still have episodes of cold and we need to quickly cool the city”, explains Pierre Athanaze, vice-president of the metropolis in charge of the environment. Because Mediterranean vegetation, to protect itself from heat and dryness, voluntarily shuts down its evapotranspiration mechanisms. However, it is this function that allows a tree to take on the role of a natural air conditioner. The metropolis therefore relies on local species (lime, maple, ash) to ensure freshness. While street trees were planted 14 meters apart in the 1970s, “to leave two parking spaces between two trees”, he notes, it is now about planting dense and tight. Rue Garibaldi, a busy thoroughfare, serves as a benchmark. Medium-sized trees, shrubs and ground covers were planted around the taller trees and the temperature under this cover measured. “With these four strata of vegetation, we gain 4.5°C during the four summer months, and 7.4°C during heatwaves, compared to a simple plane tree”underlines Pierre Athanaze.
Scenarios informed by scientific literature
It is an in-between that is offered, in fictional scenarios informed by existing scientific literature, by the consulting firm BL Évolution, specializing in supporting territories on climate issues. In the series “France at +2°C“, the engineers have created six life stories which give an idea of everyone’s reality, in the countryside as in the city, in the mountains as on an island, in a territory – France – subject to extreme climatic events which have become currency current. Why not +4°C? “If climate change is a staircase, before reaching +4°C, we will have to take the step of +2°C. However, it is already a chaotic world which will arrive in the near future, within ten at twenty years old, for which we we are not prepared and in which we do not want to live “, responds Alexandra Watier, energy-climate consultant at BL Évolution and co-author of the series.
The epic tale of Richard, one of the six fictional characters, provides an insight into this. This executive wakes up in Paris, caught in the heatwave. The weather forecast is 50°C. Richard paid a lot for his apartment located near an urban forest which still provides a little coolness. That day he must go to Carcassonne (Aude) for a meeting sealing his appointment to a position he covets. In a capital without public transport, at a standstill for several days to prevent travel during extreme heat, without an electric bike, discharged by the effect of massive power cuts, will it arrive in time? The Paris-Bordeaux rail network is out of service due to the temperature. Richard is diverted on a Paris-Lyon, then stuck in Montpellier, as a very violent Mediterranean episode approaches. The taxi he decides to take must itself leave the highway cut off by the storm. At the end of the journey, his meeting is canceled.
“There is a global lack of risk perception, explains Alexandra Watier. Climate change is going to disrupt our ways of organizing so much! It is about providing elements for help raise awareness of this. “Richard’s adventures tell of the need for naturally ventilated buildings, electrical networks resilient to heat unknown in our latitudes, non-deformable rails, resistant air-conditioned wagons. But also the need to question certain uses, at certain times So, is it possible to adapt all the infrastructures so that this trip takes place at all costs or should we temporarily abandon the latter?
Because adaptation to the impacts of climate change will weigh very heavily on public finances. To prepare, should we invest in unsinkable roads? Or rather imagine temporary closures of certain roads, not serving critical uses, such as a school or a hospital, during flood episodes? “Technically, we would be able to adapt to everything, but the cost would be too high “, explains Vivian Dépoues, researcher at the Institute for climate economics (I4CE).
He is the author of the report “Anticipating the effects of 4°C warming: what are the costs of adaptation?“, which presents costing elements: 1 and 2.5 billion additional euros per year to systematically take heat waves into account in the construction of new housing, “a few hundred million to a few billion euros of additional investments in the coming decades ” for rail and road networks. For the researcher specializing in adaptation, there is no need to imagine the Apocalypse. “At +4°C, not all transport networks will suffer a permanent cataclysm, but the level of service will perpetually deteriorate: without adaptation, managers will spend their time chasing repairs, structural work will be postponed and the material will deteriorate “, explains Vivian Dépoues.
In Gironde, Lacanau is reorganizing facing the ocean
Perhaps one day there will be a dune in place of the dike that protects Lacanau. But, until at least 2050, it is a question of keeping the structure in place, increasingly attacked by erosion and waves. A period of time necessary to allow the seaside resort of Gironde to reorganize itself in order to anticipate the effects of climate change which subject it to increased risks of submersion in particular. Next winter, the seafront car parks will be dismantled, the first aid stations and the Maison de la gliding moved back. The cost of these operations is estimated at more than 13 million euros.
Lacanau has long been attacked by coastal erosion. About ten years ago, the town considered moving housing from the seafront. An operation with staggering costs, nearly 500 million euros, deemed impossible. “We can’t move a city like that, we can’t raze neighborhoods! “, explains Nicolas Castay, director of the Littoral Aquitain public interest group. But the effects of warming are now cumulative and inaction would be too expensive. In a pessimistic scenario, by 2100, nearly 20,000 housing units, representing a value of more than 6 billion euros, and more than 1,800 business premises are threatened in the Gironde department.
The dike which protects Lacanau from the onslaught of the ocean must be regularly reinforced until the seaside resort takes a more radical decision, such as moving businesses and housing built on the seafront. Credit: BAPTISTE FENOUIL/REA
Plan now to adapt infrastructure
To anticipate, it is imperative to project, locally, the time remaining before reaching certain levels of warming. For buildings and railway tracks, it is therefore urgent to imagine a territory at +4°C. “We will not renovate housing twice between now and the end of the century, it is both too complicated and too expensive, the same goes for railway tracks and equipment. “, notes Vivian Dépoues. On the other hand, the roads have more time ahead of them. “The bitumen of a departmental road must be changed every ten to fifteen years, there is no point in wanting to replace it with a mixture resistant to +4°C!, he adds. But we must integrate the reflex of asking ourselves the question at each deadline. However, for the moment, in all the norms, the standards, the technical benchmarks, future climatic conditions do not make reference. “
Resolving the associated technical and financial dilemmas will not be enough. It does not say the capacity of a municipality, a neighborhood, a family to reorganize itself in the event of a climate crisis, nor the mutual aid networks already existing or to be created, nor finally the capacity of inhabitants to invent solutions. alternative modes of travel or work. More than 2 degrees of additional warming will have effects on the core of our lives. “What relationship will we have with the seasons? What sports will we be able to practice? Will we be able to keep the same hobbies? Climate change will have an impact on our resources, but also on our culture, our identity, our values! We must prepare for it while succeeding in the ecological transition, it is an opportunity to question our lifestyles “, insists Alexandra Watier. Fundamental battles to be fought head-on.
In the Jura, the Métabief resort anticipates the end of skiing
Métabief is not waiting for the effects of warming. In 2050, the viability of skiing in this mid-mountain resort in the Jura massif – between 1000 and 1400 meters above sea level – is estimated at zero. These were the conclusions of the ClimSnow study (2020), a method deployed by Météo France and INRAE which makes it possible to quantify the reliability of snow cover. By this date, the resort will have put an end to this activity twenty years ago, i.e. in 2030. Giving up skiing makes Métabief a pioneer in the adaptation of mountain areas. “The key is that this decision came from professionals in the field, from those who make a living from skiing, who understood that protecting jobs meant not locking ourselves into a system “, explains Olivier Erard, a trained glaciologist who for ten years directed the Mont d’Or Mixed Union, the linchpin of this shift.
Rather than planning the costly replacement of the chairlifts, elected officials agreed to invest in their maintenance, in order to simply extend their life. And to think now about a new model, while skiing still represents half of the region’s tourist economy. Mountain biking, disabled sports, trail… Reconfiguring the ski resort into a “mountain resort” is a gamble. “We don’t yet know what it will look like in five years, but getting moving, working on it, is what allows you to swallow the pill of renunciation “, notes Olivier Erard.
By Cécile Cazenave
