WMO confirms 2025 was one of the three warmest years ever recorded

The World Meteorological Organization (WMO), a specialised United Nations agency based in Geneva, confirmed in an official statement on 14 January 2026 that 2025 had been one of the three warmest years since continuous temperature measurements began (1850). According to a consolidated analysis of eight global meteorological datasets, the mean surface temperature in 2025 was 1.44 degrees Celsius above the pre-industrial 1850-1900 average, with an uncertainty interval of plus or minus 0.13 degrees. The absolute mean global temperature stood at 15.08 degrees, the report says.

The analysis drew on eight datasets from different national meteorological services and scientific institutions, among them ERA5 (the European Centre for Medium-Range Weather Forecasts, ECMWF), JRA-3Q (the Japan Meteorological Agency), GISTEMP v4 (NASA Goddard Institute for Space Studies), NOAAGlobalTemp v6 (the United States NOAA), HadCRUT5.1.0.0 (Britain’s Met Office and the University of East Anglia), Berkeley Earth, DCENT and CMST. Two datasets (DCENT and GISTEMP) ranked 2025 as the second warmest, while the remaining six placed it third. The warmest year on record across all datasets remains 2024.

In methodological terms, the consolidated WMO report is the standard format the agency has published since 1993. The 1850-1900 period is used as the pre-industrial baseline because the global mean temperature is taken to have been relatively stable in that interval, before anthropogenic greenhouse-gas emissions began to drive accelerated warming. Under the Paris Agreement, that period provides the baseline for the goal of keeping the temperature rise well below 2 degrees Celsius, with the aim of 1.5 degrees.

What the warming means in a wider context

The period from 2015 to 2025 is the warmest 11-year run in the history of measurement, the WMO says, while the last three years (2023, 2024 and 2025) take the top three places across all eight datasets. WMO Secretary-General Celeste Saulo said in the statement that “2025 began and ended with cooling from La Niña, and yet was one of the warmest years ever recorded, because of the accumulation of greenhouse gases that trap heat in the atmosphere”. Ocean heat content rose by around 23 plus or minus 8 zettajoules compared with 2024, while 33 percent of the global ocean had a surface temperature in the three warmest recorded categories.

Other indicators in the report: the mean sea-surface temperature was 0.49 degrees above the 1981-2010 average; annual Arctic sea-ice extent was at or near a record low; Antarctic sea ice had its third-lowest extent on record; glacier melt continues unabated. For the first time in the history of this report, the WMO has also included so-called Earth Energy Imbalance, an indicator that measures the gap between the energy the planet receives from the Sun and the energy it radiates back to space.

The limits of these measurements are worth weighing. A distinction has to be drawn between an annual temperature jump (which can be amplified by natural cycles such as El Niño) and the long-term climate signal, which is read off five-year or ten-year averages. Under the new WMO Decadal Climate Update (2025-2029), the five-year mean temperature for 2026-2030 is, with 80 percent confidence, expected to fall between 1.2 and 1.9 degrees above the pre-industrial average. In other words, a single year above 1.5 degrees does not automatically mean the Paris Agreement threshold has been breached, since that target refers to a long-term mean. IPCC assessments due in the seventh reporting cycle (by 2029) will give more precise contours of where the climate system actually sits.