Global average temperatures in 2024 were the hottest on record, surpassing the previous record set in 2023 by a clear margin. In three global temperature assessments released on 10 January, climate scientists reported that temperatures across the world rose faster than expected, reaching 1.46°C–1.62°C above the preindustrial baseline.
“The long-term trends are very, very clear,” Gavin Schmidt, director of the NASA Goddard Institute for Space Studies, told reporters at a 10 January briefing. “It’s warming more over the land than it is over the ocean. It’s warming more in the Northern Hemisphere, where there’s more land, than in the Southern Hemisphere, where there is less. And it’s warming most of all in the Arctic regions.”
In both 2023 and 2024, global average temperatures were hotter than expected, bucking the linear heating trend that had persisted for decades. Scientists believe that a combination of factors—but primarily record high greenhouse gas emissions—contributed to the recent warming acceleration.
“The abrupt new records set in 2023 and 2024 join other evidence that recent global warming appears to be moving faster than expected,” Robert Rohde, chief scientist at climate research nonprofit Berkeley Earth, said in a statement. Their report calls the recent trend an “exceptional warming spike.”
“Whether increased global warming is a temporary change or part of a new long-term trend remains to be seen,” Rohde said.
Record Warmth Across the Globe
Analyses from NOAA and NASA found that global average temperatures were 1.46°C–1.47°C (2.63°F–2.65°F) above the preindustrial baseline of 1850–1900, and 0.10°C (0.18°F) hotter than in 2023, the previous hottest year ever recorded. Berkeley Earth’s report concluded that temperatures were 1.62°C (2.91°F) above the preindustrial baseline.
Global average temperatures on both land and in the ocean were the hottest on record. Nowhere on Earth was there a record cold year.
“All of the groups agree, regardless of how they put the data together, regardless of what data they’re using,” that 2023 and 2024 were far hotter than expected.
The NASA, NOAA, and Berkeley Earth temperature assessments differ primarily because of a choice in sea surface temperature datasets for the baseline reference period of 1850–1900. This typically results in the Berkeley Earth global average temperature calculation being hotter than the NASA and NOAA assessments. However, the teams generally use similar techniques and climate models, and so assessments for more recent years are more in agreement than those from the early 20th century.
Despite small differences, “all of the groups agree, regardless of how they put the data together, regardless of what data they’re using,” that 2023 and 2024 were far hotter than expected, Schmidt said.
Not only was 2024 the warmest year when averaged across the globe, but it was the warmest year at the local scale, too. Scientists at Berkeley Earth calculated that 32% of land areas and 21% of ocean areas had the warmest year on record for the region. For 3.3 billion people across 104 countries, 2024 was their hottest year ever.
Since 1970, global warming has proceeded at a roughly linear pace. But in 2023 and again in 2024, global temperatures rose faster than this rate. The shift in 2023 from La Niña to El Niño conditions played a small role, as did the peak of the 11-year solar cycle and the lingering presence of atmospheric water vapor from the 2022 Hunga Tonga eruption. Nonetheless, scientists at Berkeley Earth concluded that there was only about a 1% chance that the warming spike could have occurred naturally.
By far the most important factors for 2024’s warming were that humans emitted more greenhouse gases than ever before and they emitted fewer sulfur aerosol particles over the ocean. Sulfur aerosols are reflective, so they slightly reduce heat from incoming sunlight. Aerosols can also help seed condensation and cloud formation, further reducing temperatures. A 2020 international rule reduced shipboard aerosol pollution to improve air quality.
“In general, sulfur aerosols are believed to have masked some of the effects of global warming,” the Berkeley Earth assessment reported, by artificially increasing Earth’s albedo and increasing cloud coverage, both of which provided a modest cooling effect. That mask has been somewhat lifted. “It is…reasonable to anticipate that global warming may continue to accelerate if additional reductions in sulfur air pollution are undertaken.”
Can We Still Meet Climate Goals?
International organizations have found that the world is offtrack for limiting global warming to less than 1.5°C (2.7°F), a political goal set by the 2015 Paris Agreement. This is the second year for which Berkeley Earth has reported a global average temperature increase higher than 1.5°C. Other groups have done so as well, though NASA and NOAA have not. Berkeley Earth concluded that remaining below a long-term average of 1.5°C hotter than preindustrial temperatures is now “unobtainable” and that “the long-term average will pass this milestone within the next 5–10 years,” Rohde stated.
This ambitious warming target, as well as a now more realistic one of 2°C (3.6°F), is based on multidecadal averages, so a few years above these thresholds do not yet constitute a failure to achieve these goals.
However, Schmidt cautioned that this ambitious warming target, as well as a now more realistic one of 2°C (3.6°F), is based on multidecadal averages, so a few years above these thresholds do not yet constitute a failure to achieve these goals.
“Even if we likely exceeded [1.5°C] this year, that doesn’t mean that we’ve exceeded it in the context of the Paris accord, which is over a longer time period,” Schmidt said. “But I will say that we anticipate future global warming as long as we are emitting greenhouse gases, and until we get to net zero, we will not get a leveling off of global mean temperature.”
He added that temperature uncertainties from the early 1900s mean that humanity probably won’t definitively know when temperature thresholds are breached until after it happens, but that NASA and NOAA project it may happen in the mid-2030s or 2040s.
Nonetheless, every fraction of a degree of warming matters, the NOAA and NASA scientists warned. People around the world are already experiencing devastating climate impacts. Drought and wildfire ravage communities, sea level rise encroaches on small island nations, and flooding and landslides threaten billions around the world.
“The changes occurring in people’s everyday weather experiences have become abundantly clear,” Schmidt said.
“This is no longer an esoteric academic exercise,” he added. “This is now quite personal.”
—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer
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