The UN weather agency confirms 2015-2025 as the hottest 11 years on record, with 2025 ranking second or third hottest and Earth’s energy imbalance at a record high, warning of centuries-long warming consequences.
In its State of the Global Climate 2025 report, released today, the World Meteorological Organization (WMO) has said that the 2015 to 2025 has been the hottest 11-year period since reliable records began in 1850.
Global near-surface temperatures in 2025 averaged about 1.43°C ± 0.13°C above the 1850-1900 pre-industrial baseline, ranking the year as either the second or third warmest on record depending on the dataset. The previous year, 2024, remains the hottest at approximately 1.55°C above pre-industrial levels, driven initially by a strong El Niño event before a shift to La Niña conditions provided temporary cooling.
This marks the continuation of an alarming trend. Humanity has now endured eleven consecutive years of record heat, a pattern United Nations secretary-general António Guterres described as no longer coincidental but “a call to act.” The findings underscore how greenhouse gas concentrations – carbon dioxide, methane, and nitrous oxide – reached levels unseen for hundreds of thousands to millions of years, with the 2024 annual increase in atmospheric CO₂ marking the largest since modern measurements began in 1957.
Earth’s Energy Imbalance Hits New High
For the first time, the WMO report prominently features Earth’s energy imbalance as a core climate indicator. Under stable conditions, incoming solar energy roughly equals outgoing energy. However, rising greenhouse gases have disrupted this equilibrium, trapping excess heat at the highest rate observed in the 65-year record. In 2025, the imbalance reached unprecedented levels.
The ocean has absorbed the equivalent of about 18 times annual human energy consumption each year for the past two decades, acting as a massive buffer, the report says. Ocean heat content hit a new record in 2025, with its warming rate more than doubling between 1960-2005 and 2005-2025. Only about 1 per cent of excess energy warms the atmosphere near the surface – the temperatures humans experience – while over 91 per cent is stored in the oceans, 5 per cent in land masses, and 3 per cent goes toward melting ice.
WMO Secretary-General Celeste Saulo emphasised: “Scientific advances have improved our understanding of the Earth’s energy imbalance and of the reality facing our planet and our climate right now. Human activities are increasingly disrupting the natural equilibrium and we will live with these consequences for hundreds and thousands of years.”
Oceans, Ice Sheets and Sea Levels Under Severe Strain
The cryosphere is melting at accelerating rates. Arctic annual average sea-ice extent in 2025 was the lowest or second-lowest in the satellite era (since 1979), while the winter maximum extent hit a record low of about 14.19 million km². Antarctic sea-ice extent ranked third-lowest on record, with the past four years producing the four lowest summer minima.
Glacier mass loss ranked among the five worst years since 1950, with exceptional declines in Iceland and along North America’s Pacific coast. These changes, combined with ocean expansion, drove global mean sea level in 2025 to levels comparable with the 2024 record – approximately 11 cm higher than at the start of satellite measurements in 1993. The rate of rise has accelerated since 2012.
Such changes are largely irreversible on centennial to millennial timescales, according to Intergovernmental Panel on Climate Change projections cited in the report.
Extreme Weather Takes Deadly Toll
The imbalance manifests daily as more extreme weather. In 2025, heatwaves, wildfires, droughts, tropical cyclones, storms, and flooding caused thousands of deaths, affected millions of people, and inflicted billions of dollars in economic losses. Cascading impacts hit agriculture, food security, migration, and biosecurity hardest in vulnerable and conflict-affected regions.
Guterres warned: “On a day-to-day basis, our weather has become more extreme… And in this age of war, climate stress is also exposing another truth: our addiction to fossil fuels is destabilising both the climate and global security. Today’s report should come with a warning label: climate chaos is accelerating and delay is deadly.”
Leaders Call for Immediate Action
The report arrives on World Meteorological Day under the theme “observing today to protect tomorrow.” It highlights how interconnected economies and societies remain vulnerable despite scientific progress. Governments pledged under the 2015 Paris Agreement to limit warming to well below 2°C, preferably 1.5°C, yet current trajectories show the planet is being “pushed beyond its limits,” with every key indicator “flashing red,” Guterres stated.
Saulo added that while weather has always varied, the current pace and scale of change are unprecedented in human history. The WMO, he said, urges accelerated emission reductions, strengthened early-warning systems, and enhanced adaptation measures to safeguard lives and livelihoods.
