The past 11 years (2015-2025) have been the hottest on record, with last year being the second or third warmest year since observations began, according to a report released today by the World Meteorological Organization (WMO).
The State of the Global Climate 2025 report, which tracks important climate indicators, found that atmospheric carbon dioxide concentrations and ocean temperatures reached record levels last year. Global surface temperatures were slightly lower in 2025 than the previous year — the hottest on record — but continued a run of exceptionally high temperatures, the report states. The amount of sea ice in the Antarctic and the Arctic was among the lowest recorded since 1979.
The speed at which temperatures are rising, the ocean is heating up and glacial ice mass is melting is concerning, says Mandy Freund, a climate scientist at the University of Melbourne in Australia.
“We seem to be entering this new era where temperatures will be significantly higher than what they were ten years ago,” says climate scientist Sarah Perkins-Kirkpatrick, who is from the Australian National University in Canberra. The past three years have seen large changes in temperature that could only be a result of climate change, she adds.
Energy imbalance
For the first time, the report includes a measure of the accumulation of heat on Earth and in the atmosphere. The indicator, called the Earth’s energy imbalance (EEI), has been used by climate scientists for at least a decade, and is the difference between the amount of energy that the Earth receives from the Sun and the amount radiated back into space. It allows scientists to monitor the rate of global warming. A positive EEI value means that the total amount of heat stored on Earth is increasing.
Last year, the EEI reached its highest level since observations started in 1960, the report states. The increased concentration of greenhouse gases in the atmosphere traps heat on Earth, reducing the amount of warmth that is radiated back into space.
Thomas Mortlock, a climate analyst at the University of New South Wales in Sydney, Australia, says that the inclusion of EEI in the WMO report is notable. Typically, the rise in surface temperatures is what makes headlines, but the atmosphere absorbs just 1% of the planet’s excess heat so using it to gauge the severity of global warming is “quite misleading”, he says. More than “91% of all of the excess heat that has been received by the Earth since the 1970s has been absorbed in the oceans”, he adds.
Mortlock suggests that the planet’s energy imbalance is a much better descriptor to understand the true impact of global warming.
Freund adds that EEI is also a clearer measure of long-term changes than comparing average temperatures, which can fluctuate year to year owing to events with short-term impacts, such as volcanic eruptions or the La Niña weather pattern.
