World likely to overshoot the 1.5°C climate limit, scientists say

The world has just recorded its first three-year run of average temperatures close to or above 1.5 degrees Celsius above pre-industrial levels, with 2023 and 2025 nearly reaching that mark and 2024 hitting 1.55 degrees. The World Meteorological Organization has already confirmed that 2024 was the first calendar year to breach 1.5°C, based on an average across six temperature datasets, though individual datasets ranged from 1.46°C to 1.66°C depending on how they measure ocean temperatures historically. The Paris Agreement's 1.5°C target, set in 2015, is technically measured as a 20-year average to smooth out natural swings like El Niño, so a few hot years do not formally break it. But scientists say the long-term average is now on track to cross that threshold within five to ten years, and some say it may already be effectively unreachable.

Robert Watson, a former chair of the Intergovernmental Panel on Climate Change, put it bluntly: "Climate policy has failed. The 2015 landmark Paris agreement is dead." At a briefing, Copernicus scientist Samantha Burgess said there is "an extremely high likelihood that we will overshoot the long-term average of 1.5°C and the Paris Agreement limit." Not everyone agrees the goal is fully out of reach: Duo Chan of the University of Southampton, who helped build a new temperature dataset suggesting 2024 warming reached 1.66°C, still says "it's too early to give up" on cutting emissions.

Part of the recent surge is tied to El Niño, a natural warming pattern in the Pacific Ocean that temporarily pushes global temperatures higher. A World Meteorological Organization forecast estimated a 66% chance that at least one year in the coming five years would cross 1.5°C, and a 98% chance that at least one of those years would be the hottest on record, driven partly by an expected El Niño on top of the underlying warming trend. But temperatures stayed at record levels even after that El Niño ended in 2024, which surprised many scientists who expected them to ease off.

A deeper reason is that the planet's natural buffers against carbon dioxide are weakening at the same time emissions remain high. For decades, oceans and forests have absorbed roughly half of the carbon dioxide humans emit, cushioning the warming. Now oceans are becoming more layered by temperature, which limits how much carbon dioxide they can pull from the air, and trees are increasingly damaged by heat, drought, and wildfires, which have doubled globally over the past twenty years. Researchers have reported an "unprecedented" weakening of land-based carbon sinks in 2023 and 2024, and African rainforests, once responsible for about a fifth of the carbon dioxide absorbed on land, have shifted from a carbon sink to a source, according to Yale Environment 360's reporting on recent studies.

Scientists' central worry is not just that the world will get hotter, but that certain changes could become permanent once triggered — points of no return known as tipping points. Greenland is currently losing 30 million tons of ice every hour, and Watson says the "current best assessment" is that this melting could become unstoppable around 1.5°C of warming; the ice sheet holds roughly 2,800 trillion tons of ice that would, if it all melted over centuries, raise global sea levels by about 23 feet. The West Antarctic Ice Sheet faces a similar risk. Tropical coral reefs may have already passed a tipping point toward mass die-off, with some studies suggesting reefs worldwide could be dead by mid-century.

Ocean currents that redistribute heat around the planet may also be at risk. The Atlantic Meridional Overturning Circulation, a system of currents that currently helps warm Europe and the eastern coast of North America, could weaken or shut down; James Hansen of Columbia University has argued this is "likely within the next 20-30 years" without action to curb warming, though other studies suggest a shutdown is unlikely this century. A 2025 Global Tipping Points Report led by Tim Lenton of the University of Exeter warned that a failure of this circulation would "plunge northwest Europe into prolonged severe winters." A modeling study by the Potsdam Institute found that if the world does not return to 1.5°C by 2100, there is a one-in-four chance that at least one major threshold — among the Atlantic circulation, the Amazon rainforest, or the Greenland or West Antarctic ice sheets — will be crossed, and co-author Annika Ernest Högner noted that risks would "escalate even more rapidly" past 2°C. Scientists also warn of a domino effect, where crossing one tipping point helps trigger another, such as Greenland's melt disrupting the Atlantic circulation in a way that further stresses the Amazon.

Because tipping points are difficult to model precisely, they are often left out of climate projections altogether, and are still largely absent from the calculations of climate negotiators. Manjana Milkoreit of the University of Oslo, a lead author of the 2025 Global Tipping Points Report, says "current policy thinking doesn't usually take tipping points into account." Meanwhile, global emissions of carbon dioxide from burning fossil fuels reached a new high in 2025, according to provisional data cited by the BBC, and the most recent UN climate summit, COP30, failed to directly mention fossil fuels in its final agreement. The United States withdrew from the Paris Agreement in January 2026, leaving Iran, Libya, and Yemen as the only other UN member states outside the pact.

Efforts to pull carbon back out of the atmosphere, needed to reverse any overshoot, currently fall far short of what would be required. Forest protection and restoration projects are absorbing an estimated 2 billion tons of carbon dioxide annually, but the IPCC estimates that lowering global temperatures by even 0.1°C would require roughly a hundred times that amount, and some recent studies suggest 400 billion tons might be needed to return to 1.5°C by 2100. Industrial carbon capture, using chemical plants to extract carbon dioxide from the air, remains, in the words of Yale Environment 360, "prohibitively expensive." UN Secretary-General António Guterres has said he still hopes temperatures could be brought back down to the 1.5°C target by the end of the century, and scientists stress that sharp emissions cuts can still meaningfully limit future warming and its impacts.