The sun sets on a hot day in London in July 2024
Guy Corbishley/Alay
Hopes of keeping global warming below 1.5°C above pre-industrial levels have faded after new data confirmed that 2024 was the first calendar year in which average temperatures exceeded that critical threshold.
Last year was the hottest ever recorded in human history, the World Meteorological Organization (WMO) will declare later today, in its latest stark warning, that humanity is pushing Earth’s climate into uncharted territory.
The annual average global temperature exceeded 1.5°C above the pre-industrial baseline for the first time, the agency will also confirm, surpassing the threshold set by the Paris Agreement.
The WMO assessment is calculated using the average global temperature from six datasets, with the period 1850-1900 used to provide a pre-industrial baseline. Temperature datasets collected by various agencies and organizations around the world vary somewhat, mainly due to differences in how ocean temperatures have been measured and analyzed over the decades. Some of these datasets will be below the 1.5°C mark, The New Scientist understand, but others are far superior.
The UK’s Met Office weather service puts the average temperature in 2024 at 1.53°C above pre-industrial levels, with a margin of error of 0.08°C. This is more than 0.07°C since 2023, the warmest previous year on record. Meanwhile, the European Union’s Copernicus climate change service has 2024 temperatures at 1.6°C above pre-industrial levels, 0.12°C above the 2023 record.
Scientists agree that the rise in temperatures is mainly caused by the continuation of human-caused climate change and an El Niño weather pattern, which tends to increase global temperatures. But the scale and duration of the heat has surprised many experts, who expected temperatures to drop once El Niño ended in May 2024. Instead, they remained at record levels throughout the year.
The world’s oceans were the worst affected, with sea surface temperatures remaining at record levels for most of 2024, wreaking havoc with marine ecosystems. The year did not lack extreme weather on land, with strong heat waves, significant decrease in polar icedeadly floods and uncontrollable fires. “It was a year where the impacts of climate change are all over the planet,” he says David KingFormer Chief Scientific 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 using a 20-year average, so a single year above the threshold does not represent a formal breach of the goal. But given the pace of warming in recent years, many scientists say the long-term Paris goal is currently out of reach.
In a speech on January 9, Samantha Burgess Copernicus told reporters that the goal of the Paris Agreement was now impossible to achieve. “There is a high probability of exceeding the long-term average of 1.5°C and the Paris Agreement limit,” he said.
Duo Chan At the University of Southampton in the UK, he has helped develop a new global dataset, DCENT, which he says uses cutting-edge technology to create a more accurate historical baseline of warming levels. This new data set suggests that the global average temperature by 2024 was 1.66°C above pre-industrial levels, he says, although it is not in the WMO’s estimates.
As a result, Chan also believes that the 1.5°C target is now probably out of reach. “We need to prepare for a wider range of futures, and 1.5°C is not the only target we should be aiming for,” he says. But he emphasized that it must also be a critical moment to be more ambitious in 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 beginning to cool to expected levels. “That’s a good sign that at least heat is being dissipated from the surface of the ocean,” Burgess said. Meanwhile, after months of anticipation, A La Niña phase has finally developed in the equatorial Pacific OceanWhich should lower the global temperature in 2025.
But Chan warns that the world may have experienced a warming shift if temperatures follow the pattern of previous El Niño events. “Every time we see a big El Niño event … global warming basically rises to a new level,” he says, suggesting that 2024 could be the first in many years when average temperatures exceed 1.5°C.
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