2024 confirmed as the first year to exceed the 1.5°C warming limit

Hopes of keeping global warming below 1.5°C above pre-industrial levels are all but ruled out after new data confirmed that 2024 was the first calendar year in which average temperatures exceeded the critical threshold.

Last year was the hottest ever recorded in human history, the World Meteorological Organization (WMO) declared on January 10 in the latest stark warning that humanity is pushing Earth’s climate into uncharted territory.

The average global temperature for the year exceeded 1.5°C above the pre-industrial baseline for the first time, the agency also confirmed, temporarily exceeding the threshold set by the Paris Agreement.

The WMO’s assessment is calculated from the average global temperature across six datasets, with the period 1850 to 1900 used to provide a pre-industrial baseline. Temperature data sets collected by different agencies and institutions around the world vary slightly, mainly due to differences in how ocean temperatures have been measured and analyzed over the decades. Some of these data sets come in just below the 1.5°C mark, but others are well above.

The UK Met Office weather service puts the 2024 average temperature at 1.53°C above pre-industrial levels, with a margin of error of 0.08°C. That’s 0.07°C above 2023, the previous warmest year on record. Meanwhile, the EU’s climate change service Copernicus has 2024 temperatures at 1.6°C above pre-industrial levels, 0.12°C above the 2023 record.

Berkeley Earth, a climate research group in California, finds an increase of 1.62°C, the second time in its data set that the increase in global average temperatures has reached 1.5°C after 2023. Temperature data from NASA puts the temperature increase slightly lower at 1.47° C above pre-industrial levels, and the US National Oceanic and Atmospheric Administration finds an increase of 1.46°C above pre-industrial levels. The WMO finds an average increase of 1.55°C across the six datasets with a margin of error of 0.13°C.

Scientists agree that the increase in temperature was mainly due to the continuation of human-made climate change and an El Niño weather pattern, which tends to push up global temperatures. But the extent and persistence of the heat has shocked many experts, who expected temperatures to drop when El Niño ended in May 2024. Instead, they remained at record levels for the rest of the year.

The world’s oceans have been hardest hit, with sea surface temperatures remaining at record high levels for most of 2024, devastating marine ecosystems. The year also brought no shortage of extreme weather on land, with violent heatwaves, sharp declines in the polar ice cap, deadly floods and uncontrollable wildfires. “This was a year where the effects of climate change are equal across the planet,” said David King, former chief science adviser to the UK government and founder of the Climate Crisis Advisory Group.

Technically, the Paris Agreement’s goal of limiting warming to below 1.5°C is calculated based on a 20-year average, so a single year above the threshold does not signal a formal breach of the goal. But given the pace of warming in recent years, many scientists say the long-term Paris goal is now out of reach.

“The sudden new records set in 2023 and 2024 join other evidence that recent global warming appears to be moving faster than expected,” Robert Rohde of Berkeley Earth said in a statement. “Whether increased global warming is a temporary change or part of a new long-term trend is unknown. Even though the Paris Agreement’s goal of staying below 1.5°C is unattainable, the long-term average will pass this milestone within the next five to 10 years.”

In a briefing on January 9, Samantha Burgess at Copernicus told reporters that the Paris Agreement’s goals were now likely to be unachievable. “There is an extremely high probability that we will exceed the long-term average of 1.5°C and the Paris Agreement limit,” she said.

Duo Chan at the University of Southampton, UK, has helped develop a new global dataset, DCENT, which he says uses advanced technology to produce a more accurate historical baseline of warming levels. This new data set suggests that the global average temperature for 2024 was 1.66°C above pre-industrial levels, he says, although it is not included in the WMO’s calculations.

As a result, Chan also believes that the 1.5°C target is now likely out of reach. “We need to prepare for a wider range of futures, and 1.5°C is not the only target we should aim for,” he says. But he stressed that it should also be a critical moment to be more ambitious about reducing emissions. “It’s too early to give up,” he says.

The outlook for 2025 is still unclear. There are early signs that global sea surface temperatures are finally starting to cool to expected levels. “It’s a good sign that the heat is at least going away from the sea surface,” Burgess said. Meanwhile, after months of anticipation, a La Niña phase has finally developed in the equatorial Pacific Ocean, which should moderate global temperatures into 2025.

But Chan warns that the world may have seen a step change in warming if temperatures follow the pattern of past El Niño events. “Every time we see a big El Niño event … global warming is basically brought to a new level,” he says, suggesting that 2024 could be the first of many years in which average temperatures exceed 1.5°C.