The planet is increasingly falling “out of balance”, as more heat becomes trapped in the atmosphere, accelerating global warming. The past eleven years have been the warmest on record.
According to a report by the World Meteorological Organization (WMO), the period 2015–2025 marks the hottest decade ever recorded. The report also notes that 2025 ranks as either the second or third warmest year since observations began.
Record-breaking climate indicators
As reported by Nature, the study titled State of the Global Climate 2025 tracks key climate indicators and found that atmospheric carbon dioxide concentrations and ocean temperatures reached record highs last year.
Global surface temperatures in 2025 were slightly lower than the previous year, the warmest on record, but remained within a sustained period of exceptionally high temperatures.
At the same time, sea ice levels in both Antarctica and the Arctic were among the lowest recorded since satellite monitoring began in 1979.
“The speed at which temperatures are rising, the ocean is warming, and ice mass is melting is alarming,” said Mandy Freund, a climatologist at the University of Melbourne.
Sarah Perkins-Kirkpatrick, from the Australian National University in Canberra, warned that the planet appears to be entering a new phase. “We seem to be moving into an era where temperatures will be significantly higher than they were just a decade ago,” she said, adding that the sharp changes observed over the past three years can only be explained by climate change.
Measuring the planet’s energy imbalance
For the first time, the WMO report includes a measure of how much heat is accumulating within the Earth system and its atmosphere. This indicator, known as Earth’s Energy Imbalance (EEI), represents the difference between the energy the Earth receives from the Sun and the amount it radiates back into space. It allows scientists to track the pace of global warming more accurately. A positive EEI indicates that the planet is gaining heat. According to the report, EEI reached its highest level on record in 2025, with observations dating back to 1960. The increase is driven by higher concentrations of greenhouse gases, which trap heat and reduce the amount released back into space.
Thomas Mortlock, a climate analyst at the University of New South Wales in Sydney, described the inclusion of EEI in the WMO report as significant. Surface temperature trends typically dominate headlines, but the atmosphere absorbs only about 1% of the planet’s excess heat. “Relying solely on atmospheric temperatures to assess global warming can be quite misleading,” he said. More than 91% of the excess heat accumulated since the 1970s has been absorbed by the oceans, making them a critical indicator of climate change.
Mortlock added that Earth’s energy imbalance provides a more comprehensive understanding of the true scale and impact of global warming.
Source: CNA