The World Meteorological Organization warns disrupting the earth's energy equilibrium is locking in climate consequences for hundreds of thousands of years, including ongoing polar ice melt and sea level rise.
As well as including planetary energy imbalance as a climate indicator for the first time, WMO's State of the Global Climate report confirms the world had sweltered through its hottest 11 years on record.
Last year marked either the second or third warmest on record, depending on the data source.
"On a day-to-day basis, our weather has become more extreme," said Celeste Saulo, secretary-general of the UN climate and weather agency.
"In 2025, heatwaves, wildfires, drought, tropical cyclones, storms and flooding caused thousands of deaths, impacted millions of people and caused billions in economic losses."
Australia has just suffered through another summer of extremes, characterised by accelerating "climate whiplash" between fires, heatwaves, floods and storms, as described by the Climate Council.
A tropical cyclone system has just barrelled through far north Queensland and the Northern Territory, fuelled in part by record-breaking ocean temperatures in the Coral Sea.
The world's oceans absorb much of the excess heat in the atmosphere - 91 per cent - caused by more greenhouse gases trapping in warmth from the sun's rays, the WMO said.
For the past two decades, oceans have been absorbing the equivalent of about 18 times yearly human energy use, helping to buffer heating felt on land but causing coral bleaching, tropical storms and sea ice loss.
Sea ice coverage in the Antarctic has been at record lows for the past four years.
Just one per cent of excess heat is felt near the earth's surface, with three per cent melting ice and five per cent is stored in land masses.
UN Secretary-General António Guterres said the planet was being pushed beyond its limits.
"Every key climate indicator is flashing red."
The world's "addiction" to fossil fuels was destabilising both the climate and global security, he warned.
WWF's global president Adil Najam, who is visiting Australia, said the advanced economy had a significant role to play with its abundant renewables resources.
"The question we are facing today is not whether change is needed, but how decisively and responsibly we choose to act," Dr Najam said
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