Jean-Marc Jancovici is one of the most prominent voices in France’s climate debate. Sometimes described as a prophet of doom, he has been warning about the consequences of climate change since the 1990s. His engineering background shapes the way he makes his case. Rather than appealing to morality, he focuses on physical constraints, energy flows and what is technically feasible.
His influence has long extended beyond specialist circles. In 2021, he and the artist Christophe Blain published the graphic novel Le Monde sans fin. In 2022, it became France’s bestselling book.
By May 2024, sales had exceeded one million copies – a level of success more commonly associated with literary stars such as Michel Houellebecq than with a work about climate and energy.
The book also exposed a rift between Jancovici and parts of the French environmental movement. Many environmentalists share his assessment of the climate crisis, but not his proposed response. Jancovici rejects the idea that modern industrial society can be sustained by wind turbines and solar panels alone. Instead, he argues for a combination of renewable energy, nuclear power and substantially lower material consumption.
The disagreement, then, is not over climate change itself, but over the price of abandoning fossil fuels.
The Heat Is No Surprise
Repeated heat waves have brought Jancovici back to French television studios in recent months. Invitations multiply as temperatures rise. When the weather cools, public interest fades again.
This short attention span frustrates him. In his view, recent developments should surprise no one. Climate models have long predicted that heat waves would grow more frequent and severe as average global temperatures rose. What was once exceptional is now a regular feature of summer.
The meaning of “normal” weather is changing with them. Temperatures regarded as record-breaking today may seem commonplace within a few years.
Even so, public discussion often remains fixated on the immediate consequences of extreme heat: the number of tropical days, rising sales of air-conditioning units or the opening hours of swimming pools. Yet the damage does not disappear when temperatures fall. It remains visible in the soil, forests, waterways and farmland.
A tree may survive one heat wave, but not a decade of drought. Farmers face the same problem. They may withstand one failed harvest, but several in succession can exhaust their reserves.
For now, technology can cushion some of the impact. Irrigation eases drought, imports make up for crop failures and damaged infrastructure can be repaired. Every such remedy, however, requires more money and energy.
That, in Jancovici’s view, is the trap. Climate-related damage will consume ever greater resources just as Europe’s access to oil and gas becomes less secure. He does not foresee a single moment when the system suddenly collapses. Instead, each new shock will strike when repairing the damage costs more than before – in both money and energy.
Everything Begins With Energy
For Jancovici, energy is above all what keeps machines running. Without it, freight transport, agricultural machinery, industry and healthcare would grind to a halt. Cheap, readily available energy created a world in which most people no longer work in the fields, food is transported across continents and ordinary households can draw on the power of hundreds of machines. As Jancovici puts it, every European now commands an amount of energy that would once have required the labor of dozens of people.
Fossil fuels built this world and still sustain much of it. Burning them, however, is also changing the climate. Cutting emissions therefore means far more than replacing one kind of power plant with another. It requires the transformation of large parts of the economy.
This is why Jancovici supports nuclear power. Reactors generate large quantities of reliable electricity without directly burning coal or gas. They are not dependent on the weather and occupy far less land than vast wind and solar farms. He therefore regards the closure of functioning reactors as a strategic error, particularly as Europe seeks to electrify transport, heating and industry.
Nor does he dismiss renewable energy. He expects it to continue expanding, but stresses its physical limits. Solar and wind output inevitably fluctuate. Batteries can shift electricity from midday to evening, but cannot easily store it from summer to winter. The greater the share of renewables in the grid, the greater the need for storage, new transmission lines and backup generation.
Even that infrastructure still depends on fossil fuels. Steelmaking, cement production, mining equipment and freight transport all rely heavily on them. The transition to a low-carbon economy will therefore have to be built largely with the very fuels it is intended to replace.
The Limits of Nuclear Power
Nuclear power is no easy solution either. New reactors take years to build, costs often exceed initial estimates and Europe will have to rebuild some of the industrial capacity it has lost if it is to construct them on a large scale.
Jancovici does not regard reliance on imported uranium as a major vulnerability. The quantities required are relatively small and, unlike oil and gas, nuclear fuel can be stockpiled for years.
Cooling poses a more immediate problem. Many reactors rely on river water, which becomes warmer and scarcer during droughts. Some plants must then reduce their output. Nuclear power is therefore not immune to the effects of climate change.
Nor does Jancovici claim that new reactors alone can preserve the current way of life. Analyses by The Shift Project envisage fewer cars, lower consumption of material goods and less long-distance travel. Nuclear power can cushion the decline in available energy, but it cannot prevent it altogether.
He therefore argues for restraint. This does not mean returning to a pre-industrial society or imposing a blanket ban on comfort and luxury. It means deciding in advance where energy is indispensable and where demand can be reduced. A hospital matters more than another cheap flight. Food production takes priority over an ever-growing fleet of passenger cars, many carrying only their drivers. Restraint may begin with individual choices, but it cannot remain a purely individual matter.
Such decisions will be politically unpopular. Retrofitting buildings, protecting water supplies and transforming the energy system will absorb funds that can no longer be spent elsewhere. This is not merely a matter of increasing a single line in the national budget. It requires a broader shift in economic priorities and public expectations.
Jancovici’s conclusion is an unwelcome one. Europe will have less cheap energy precisely when it needs more of it to cope with climate-related damage. Policymakers can still decide where consumption should be reduced and what they are determined to preserve. Delaying that choice will not make the shortage disappear. It will only drive up the final cost.
According to Jancovici, a more frugal way of life is coming regardless. The only question is whether it will be chosen or imposed by circumstances.