Have we already breached the 1.5°C global warming target? 

A climate protester’s flag in Düsseldorf, GermanyYing Tang/NurPhoto/Shuttersto​ckLast month, researchers confirmed that 2024 was the first year to see global average temperatures rise more than 1.5°C above pre-industrial levels. It was a symbolic moment, given the world’s collective goal, set in 2015 under the Paris Agreement, to keep long-term warming to a 1.5°C threshold. But scientists were quick to stress that this goal is based on a 20-year average temperature, so global efforts to deliver on it are still – technically at least – in play.Yet experts are increasingly asking whether shorter periods of high temperatures could be a sign that the world has already breached 1.5°C. Can we conclude that this target has bitten the dust?Vital Atlantic Ocean current is already weakening due to melting iceAdvertisementEmanuele Bevacqua at the Helmholtz Centre for Environmental Research–UFZ in Germany and his colleagues set out to investigate whether a single warm year above 1.5°C could be a signal that long-term warming will soon reach that level.Using a combination of real-world observations and climate models, Bevacqua and his team studied warming thresholds already breached between 1981 and 2014. They found that the first single year exceeding 0.6°C, 0.7°C, 0.8°C, 0.9°C and 1°C above the pre-industrial benchmark has consistently fallen within the first 20-year period in which the average temperature reached the same thresholds.By that measure, the first single year above 1.5°C puts the world within the 20-year period scientists use to define 1.5°C of long-term warming, the team concludes. “It is highly probable that we are already within the 20-year period,” says Bevacqua. “We are most likely within the first 10 years [of the period]”.The findings chime with most predictions that long-term warming will reach 1.5°C by the late 2020s or early 2030s. It is a “confirmatory result” of what researchers are already predicting, says Paulo Ceppi at Imperial College London.But monthly temperature data may tell a different, more concerning, story. June 2024 was the 12th month in a row with average global temperatures at least 1.5°C above pre-industrial levels. In a separate study, Alex Cannon at Environment and Climate Change Canada used a climate model to compare the first time global temperatures reach 1.5°C for 12 consecutive months with the time when the 20-year temperature average crosses 1.5°C.He found that, in climate model simulations, a run of 12 consecutive months above 1.5°C indicates an 80 per cent likelihood that long-term warming of 1.5°C has already been reached, even when natural variability such as El Niño phases are accounted for. “If you shift back into the real world, that would imply that there’s a good probability we have already passed the long-term threshold [for 1.5°C],” he says.However, the conclusions are based on a climate model that assumes Earth’s atmosphere is very responsive to