The world is almost certain to surpass 1.5°C of global warming within the next few years, according to a new report from the UN Environment Programme (UNEP). The report acknowledges this overshoot as a near certainty, yet it maintains that a return to that temperature threshold by the end of the century remains technically possible. The key question, scientists say, is whether such a reversal is realistic.
The 1.5°C target, adopted as part of the Paris Agreement in 2015, has long been considered ambitious. The UNEP report now serves as an official recognition of what many researchers have argued for years: current fossil fuel emissions are set to push the planet past this limit. Inger Andersen, UNEP’s executive director, insists the target is not abandoned. “Even if we exceed 1.5, let’s be very clear: that 1.5 target is still the goal. But now we need to approach it differently, from above,” she said.
The report outlines a scenario in which rapid emissions cuts and massive-scale carbon dioxide removal bring warming back to 1.5°C by 2100. Achieving this would require limiting peak warming to no more than 1.8°C, according to report author Debra Roberts of the University of KwaZulu-Natal in South Africa. Beyond that level, irreversible changes could trigger cascading effects that make a return far more difficult. Roberts emphasized that even a successful return would not restore the world to its previous state. “Some losses will be irreversible, which means returning to 1.5 doesn’t mean we return back to the same world we left,” she said.
The report also details the severe consequences of overshooting, including increased food and water insecurity, physical and mental health impacts, and damage to homes and infrastructure. Roberts said the world is not prepared for these conditions. “Therefore we have to advance our adaptation and development strategies to deal with those higher levels of warming, the greater range of risks and impacts,” she said. “Adaptation needs to be transformational to allow us to plan for a changing world.”
The pathway back to 1.5°C depends on two demanding conditions. First, global emissions must be halved by 2035, according to report author Joeri Rogelj of Imperial College London. That appears unlikely, as emissions continue to rise worldwide. Second, the scenario requires carbon removal on a colossal scale: roughly 10 gigatonnes of CO2 per year, compared with current annual emissions of around 40 gigatonnes. This would mean scaling up carbon removal by a factor of about 100,000, said Reto Knutti of ETH Zurich in Switzerland, who was not involved in the report.
Knutti noted that cheap methods like planting forests cannot be expanded enough due to land constraints, while direct air capture remains prohibitively expensive. He believes the goal is technically and financially possible but not politically plausible. “We should be honest when we talk to policy-makers and the public that this is not the thing to plan for,” he said. “I think the plan should be to adapt for at least 2 degrees, if not more.”
James Dyke of the University of Exeter in the UK is even less optimistic. “There are still no credible plans for large-scale carbon dioxide removal,” he said. “Human societies must adapt and prepare for a warmer and more dangerous world that will persist potentially for centuries.”
Among the latest emissions scenarios used by climate modellers, only two imply a return to 1.5°C before 2150, according to Konstantin Weber, also at ETH Zurich. The scenario based on current policies forecasts warming of around 3°C by 2100. Oliver Geden of the German Institute for International and Security Affairs warned that the overshoot concept could become a way to mask ongoing failure. “The overshoot concept may turn out to be no more than a way to mask ongoing failure,” he said.
Despite the doubts, Weber argued that attempting the return is still necessary. “We have to give it a shot. There’s no real alternative,” he said. Andersen echoed that sentiment. “Now is the time to double down on climate action, not to give up on it,” she said. “Every fraction of a degree avoided, every year by which overshoot is shortened and every adaptation action taken will save lives, protect ecosystems and reduce economic losses.”