Extreme heat in 2023, 2024, and 2025 indicates a warming spike, a new analysis finds.
Global average temperatures in 2025 were the third hottest on record, surpassed only by 2024 and 2023, according to an analysis published by Berkeley Earth, a nonprofit climate research organization.
According to the analysis, last year’s global average temperature was about 1.35°C–1.53°C (2.43°F–2.75°F) greater than the 1850–1900 average. The previous year, 2024, was 1.46°C–1.62°C (2.63°F–2.92°F) above the preindustrial baseline, while 2023 was 1.48°C–1.60°C (2.66°F–2.88°F) above the baseline.
The report’s authors called the exceptional heat of the past 3 years a “warming spike” that may indicate an acceleration in the rate of climate change. “The warming observed from 2023 through 2025 stands out clearly from the long-term trend,” said Robert Rohde, chief scientist at Berkeley Earth, in a statement.
Such a spike may also indicate that the past warming rate is no longer a reliable predictor of future warming, the authors wrote.
“2023, 2024, and 2025 collectively cause us to rethink” Earth’s warming rate, Rohde said in a press briefing. Whether warming is accelerating or not, Earth’s temperature is rapidly exceeding key thresholds, such as the Paris Agreement limit of 1.5°C (2.7°F), he said.
“The overall trends in temperature are very consistent” among international agencies that track global temperature.
The report aligns with an analysis from NOAA’s National Centers for Environmental Information (NCEI) that also concluded that 2025 was the third-hottest year in the global temperature record. NOAA-NCEI calculated that the year was 1.17°C (2.11°F) above the 20th-century global average.
“There are different methodologies for how the global temperature [reports] are created, but the science behind it, the data behind it, by and large, are all shared,” said Karin Gleason, a climate scientist and chief of the monitoring section at NOAA-NCEI.
“The overall trends in temperature are very consistent” among international agencies that track global temperature, she said.
What’s Causing the Spike?
While global average temperatures have been increasing for more than a century, the past 3 years’ warming spike is notably extreme relative to the mostly linear trend of the past 50 years.
“The magnitude of this recent spike suggests additional factors have amplified recent warming beyond what we would expect from greenhouse gases and natural variability alone.”
“The magnitude of this recent spike suggests additional factors have amplified recent warming beyond what we would expect from greenhouse gases and natural variability alone,” Rohde said.
The report suggested that reductions in cloud cover and changes to atmospheric aerosols, particularly as a result of new regulations on sulfur pollution from ships in 2020, may be partly to blame for the spike. The Hunga Tonga volcanic eruption in 2022 may have also contributed to warming, though further research is needed to fully understand the eruption’s effects, the report stated.
The El Niño-Southern Oscillation (ENSO), a climate phenomenon that affects heat storage in the ocean, contributed to extreme heat in 2023 and 2024 during the El Niño phase, but remained in a weak La Niña condition for much of 2025. Such a condition would typically be expected to slightly cool global temperatures. Without the effect of La Niña, it’s possible 2025 would have been the hottest year ever recorded, Gleason said.
Gleason pointed out that a similar “warming spike” occurred in 2015 and 2016 as a result of a strong El Niño.
Humanity Faces the Heat
According to Berkeley Earth’s report, about 770 million people across the world experienced their local hottest year ever in 2025. The majority of the large population centers affected by this record-breaking heat were in Asia.
No place on Earth recorded the locally coldest year ever.
The report came as estimates from the Rhodium Group, a think tank, showed that the United States’ greenhouse gas emissions increased by 2.4% in 2025 after 2 years of decline. The United States experienced its fourth-hottest year ever recorded in 2025, according to an analysis from Climate Central, a nonprofit climate change research group, and another analysis by NOAA-NCEI.
The exceptional warming underscores “how essential sustained monitoring is to understanding [climate] changes in real time,” Kristen Sissener, executive director of Berkeley Earth, said in a statement. “Continued investment in high-quality, resilient, and robust open climate data is critical to ensuring that governments, industry, and local communities can respond based on evidence, not assumptions.”
The Berkeley Earth report predicted that global temperature trends in 2026 will be similar to those of 2025, with 2026 expected to be roughly the fourth-warmest year since records began.
—Grace van Deelen (@gvd.bsky.social), Staff Writer
Citation: van Deelen, G. (2026), The past 3 years have been the three hottest on record, Eos, 107, https://doi.org/10.1029/2026EO260031. Published on 14 January 2026.
Text © 2026. AGU. CC BY-NC-ND 3.0
