2025 was the third-warmest year on record, according to the World Meteorological Organization (WMO). The warmest year on record is still 2024, with 2023 coming in second.
The global average surface temperature for 2025 was estimated to be 1.44° Celsius (2.59° Fahrenheit) higher than preindustrial levels. The last 11 years have been the warmest 11 years since global records began in 1850.
“The year 2025 started and ended with a cooling La Niña and yet it was still one of the warmest years on record globally because of the accumulation of heat-trapping greenhouse gases in our atmosphere,” WMO secretary-general Celeste Saulo said in a statement.
To calculate the mean temperature of 2025, the WMO consolidated eight different data sets from agencies based in North America, Europe and Asia.
Each data set uses a different methodology, resulting in slightly different conclusions and a margin of uncertainty of ±0.13°C (±0.23°F). Six of the data sets were based on measurements made at weather stations and by ships and buoys. The other two, ERA5 by the EU-run Copernicus Climate Change Service and JRA-3Q by the Japan Meteorological Agency, are based on modeling.
Although it wasn’t the warmest year on record, 2025 was expected to be cooler due to a La Niña event, which typically lowers ocean surface temperatures.
But separate research published in January found that the world’s oceans set a heat record in 2025. Scientists estimate that ocean heat content in 2025 increased by about 23 zettajoules. That’s roughly 210 times more than all of humanity’s annual electricity generation, and the largest annual gain since 2017.
Oceans absorb about 90% of the excess heat trapped by human-caused greenhouse gases. Much of that stored energy can later drive sea-level rise and extreme weather events. “Traditionally, the air temperatures have gotten more press, but now the scientific community has realized oceans are really the key,” study co-author John Abraham, a professor of thermal sciences at the University of St. Thomas in the U.S., told Mongabay reporter Edward Carver.
In 2015, the Paris Agreement set a threshold of 1.5°C (2.7°F) of warming above preindustrial temperatures, warning that any temperature rise above this could lead to the worst outcomes of climate change. Though 2025 was perilously close to that threshold, at 1.44°C , scientists caution that we can only determine if we’ve crossed the threshold with a longer data set. Annual figures reflect short-term global temperature averages, so scientists need data sets that span decades to determine whether or not we’ve breached the threshold.
Banner image: A man cools off at the Ramlet al-Baida public beach in Beirut, Lebanon. Image by AP Photo/Bilal Hussein.
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