According to the 36th and latest iteration of the annual State of the Climate report published by the Bulletin of the American Meteorological Society (BAMS), greenhouse gas concentrations, global sea level, and ocean heat content all reached record highs during 2025. Moreover, annual average global surface temperature for 2025 was among the three highest on record – bettered only by 2023 and 2024, years influenced by warm El Niño conditions in the eastern and central Pacific Ocean. The report also points to a continued and ‘clear warming trend’, with the last 11 years being the warmest 11 years on record.
Published annually and compiled by 625 scientists from 60 countries, the report is widely regarded as the most authoritative assessment of the Earth's climate. Drawing on observations from satellites, weather stations, ocean buoys and field research, the report offers a comprehensive overview of the planet's vital signs.
Data records from the ESA Climate Change Initiative (CCI) once again helped to underpin findings in eight areas of the report: lake surface temperature, land surface temperature, soil moisture, snow, vegetation optical depth, ice sheets, ocean colour and stratospheric ozone. Their repeated inclusion reflects the scientific robustness of the CCI datasets.
Each of these satellite-derived records reveals a different aspect of the 2025 story.
Lake surface temperature: the fourth-warmest year on record
The world's lakes were, on average, 0.31 °C warmer in 2025 than during the 1995–2020 reference period. Although this was below the record set in 2024, it was still the fourth-largest anomaly since records began. Over the 1995–2025 period, lake surface temperatures rose by 0.22 °C per decade.
These findings come from the ESA CCI Lakes team, who led the chapter on lake surface water temperature in the State of the Climate report. The team calculated the global and regional anomalies using the satellite data record developed through the ESA Climate Change Initiative – a record which is now being sustained and extended operationally through the Copernicus Climate Change Service and the Earth Observation Climate Information Service.
The record allowed the team to assess 1,912 lakes worldwide in 2025 – double the number covered in 2022. Three-quarters of these lakes were warmer than the reference period, with just over a third exceeding it by more than 0.5 °C. The strongest warming was observed in lakes in Canada, China, Finland, Japan, northwestern Russia, the Tibetan area, and parts of Argentina. Meanwhile, parts of Patagonia and tropical South America were cooler than usual.
The ESA CCI Lakes project developed long-term satellite-derived records that form the emipirical evidence to chart the effects of climate change on freshwater ecosystems and water resources. As satellites measure temperature across a lake's entire surface rather than at a single sampling point, they provide a more accurate representation of how lakes respond to a warming climate.
Land surface temperature: extremes are important
The report also drew on data records made available via the ESA CCI Land Surface Temperature project. Here, contributing researchers from the University of Leicecter used observations from the Copernicus Sentinel-3B satellite to characterise and rank the maximum temperatures recorded at the land surface in 2025. The analysis covers seven-years from 2019 to 2025.
Unlike air temperature, which is measured at weather stations, land surface temperature describes the temperature of the ground itself. These temperatures range from below −30 °C in Antarctica to above 60 °C in northern Africa, north-eastern Australia, Iran, Iraq, and the United Arab Emirates. In 2025, maximum temperatures exceeded the 2019–2024 baseline by more than 10 °C in areas including eastern Antarctica, Mongolia, and the southern coasts of Iran and Pakistan. Almost half of Turkey's landmass recorded its highest maximum land surface temperature of the satellite era, as did large parts of Antarctica – although the report notes that, with only seven years of data available, these rankings should be interpreted with care.
Tracking these extremes is important as land surface temperature is closely linked to soil moisture, vegetation stress and wildfire risk. The satellite record provides consistent means of accurately monitoring across differing terrain, from remote deserts, agricultural plains through to hard-to-reach mountain ranges.
Soil moisture: the driest conditions since 1991
Globally, soil moisture was lower in 2025 than in any other year since 1991. This dryness was mainly driven by the Northern Hemisphere, with the most pronounced anomalies above 55°N – spanning the Siberian boreal forest and tundra, extending west into Fennoscandia, and covering the Canadian prairies and the Tibetan Plateau.
The widespread dryness occurred despite above-average precipitation over global land areas. The report links this apparent contradiction mainly to higher-than-average evaporation, which reduced the amount of water remaining in the upper soil layers. This highlights why long-term satellite observations of soil moisture are important: rainfall alone does not capture how much water is retained in the land surface.
The report uses the Copernicus Climate Change Service COMBINED product, which combines microwave observations from multiple satellite sensors using an algorithm developed by the CCI Soil Moisture project. Soil moisture influences the water, energy and carbon cycles, as well as shaping the risk of drought, heatwaves and wildfires..
Ozone: one good year is not a trend
One indicator looked better in 2025. The Antarctic ozone hole was smaller than average – the fourth or fifth-smallest on record depending on the metric used – and one of the smallest since 1992. This was a consequence of unusually warm Antarctic stratosphere during the year, which limited the extreme cold temperatures necessary for ozone-destroying reactions to take place. While such short-term variations tell us little about recovery, long-term stratospheric ozone profiles do. Tracked in the report using merged satellite datasets that include ESA CCI ozone data, these profiles continue to detail the slow recovery set in motion by the Montreal Protocol.
Snow, vegetation optical depth, ocean colour and ice sheets: supporting the wider assessment
Other satellite data records from ESA’s climate programme contributed to three further assessments, alongside other space-derived and in-situ sources.
In the Arctic chapter, spring 2025 snow water equivalent anomalies were compared using four different products, including CCI Snow data. While most Arctic land areas had higher-than-normal snow mass in April, parts of northern Europe had lower-than-normal values, indicating an earlier-than-normal spring thaw.
The report used the Vegetation Optical Depth Climate Archive, a satellite-based proxy for vegetation water content and density. This archive draws on retrieval and merging methods developed for the CCI Soil Moisture record. It showed sparse vegetation in Bolivia, Brazil, northern Mongolia and Paraguay, which is consistent with deforestation and land degradation, and denser growth in parts of north-eastern China and India, which is linked to intensified agriculture and reforestation.
For the Southern Ocean, the analysis used chlorophyll concentrations from the Ocean Colour CCI product. Positive anomalies dominated south of the Subantarctic Front during the summer months, particularly in the Atlantic sector, where concentrations peaked at around 0.4 mg m⁻³ – almost twice the value recorded in 2024 – relative to the 1999–2020 reference period. Weaker negative anomalies occurred north of the Subantarctic Front, particularly in the Atlantic downstream of South America, where they reached around −0.25 mg m⁻³, as well as in parts of the Indian and western Pacific sectors. As chlorophyll is an indicator of phytoplankton abundance, these records offer insight into the foundation of the Southern Ocean's food web and its role in the carbon cycle.
The report also drew on work from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE), an international collaboration supported by ESA and NASA. IMBIE brings together satellite-based estimates to assess changes in the mass balance of the Greenland and Antarctic ice sheets. In 2025, the Antarctic Ice Sheet experienced above-average surface and near-surface melt during the early and middle part of the melt season, while the Antarctic Peninsula recorded a melt index 30% above the 1991–2020 average.
From single measurements to long-term evidence
The seven contributions are connected not by the individual figures, but by the records behind them. A single year of observations produces a data point, whereas decades of consistent observations reveal a trend. ESA's Climate Change Initiative plays a significant role in this endeavour, converting decades of satellite observations into consistent, long-term datasets of essential climate variables, such as lake and land surface temperatures, soil moisture, snow, and ozone levels. By feeding into the State of the Climate report, these records provide critical evidence for international climate assessments and action.
Clément Albergel, Head of ESA's Actionable Climate Information Section: “Long, global, and consistent satellite observations allow us to place an individual year in the context of decades of change, to put today’s measurements in perspective. This is particularly important for 2025, a year without El Niño conditions, yet ranked it in the top three when it comes to global averaged surface warmth and ocean heat. ESA’s contribution spans several components of the Earth system, helping to show how these conditions compare with those of previous decades.”
All datasets underpinning these findings are freely accessible via the ESA CCI Open Data Portal.