World Meteorological Day: Ocean Heat Breaks Record, Scientists Warn
NEWS | 23 March 2026
Earth's climate is more imbalanced than at any other time on record, with 2015-2025 confirmed as the hottest 11 years on record, as highlighted by the World Meteorological Organization's annual State of the Global Climate report. Notably, ocean heat content reached a record high in 2025, as the seas continue to absorb around 91 percent of the excess energy trapped by the unprecedented levels of greenhouse gases accumulating in our atmosphere. This is the first State of the Global Climate report to include Earth's energy imbalance as a key indicator. Each year, a certain amount of solar energy reaches our planet. In a theoretical 'stable' climate, the amount of energy that comes in would roughly equate to the amount of energy that goes out. Massive amounts of greenhouse gases in the atmosphere have prevented that energy from making its way back into space. Instead, in an attempt to distribute itself across Earth, that energy is penetrating our environment, and in particular, our oceans. According to the report, just 1 percent of that excess, trapped energy is stored in the atmosphere itself. Five percent accumulates in the land (particularly in heat islands). Three percent is absorbed by ice, contributing to melting glaciers. The remaining 91 percent of excess energy absorbed by our oceans is difficult to fathom, but the report explains it in terms of stored heat. In 2025, the ocean's heat content topped the past 66 years of records, exceeding the record broken in 2024 by about 23 zettajoules: That's 23,000,000,000,000,000,000,000 joules. This is a massive jump, considering that the 14-zetta Joule difference recorded between 2020 and 2021 sounded bad at the time. It's as if, for the entirety of 2025, we have exploded 12 Hiroshima bombs in the ocean, every second of every day. And that's just the heat absorbed by the first 2,000 meters of the ocean's depths. While the ocean's ability to absorb heat and carbon dioxide seemingly 'buffers' climate change experienced on land, modeling suggests that even if humans totally cut our greenhouse gas emissions, the Southern Ocean alone would continue to release heat and perpetuate global warming for at least a century. What's more, hotter oceans fuel more extreme storms, resulting in greater frequency and intensity of extreme and lethal weather events such as Hurricane Melissa, Tropical Cyclones Senyar and Ditwah, and typhoons in Viet Nam and the Philippines, all of which occurred in 2025. It's also extremely bad news for life in the ocean – and for communities that rely on marine resources. Intense and unprecedented marine heat waves in recent years reveal the toll this supposed 'buffer' is really taking. What's more, marine heat waves often result in further release of greenhouse gases, as dead fish and other organisms decay in the aftermath. As well as solar energy, the WMO report notes the ocean has also absorbed 29 percent of carbon dioxide emissions released through human activities in the past decade. When carbon dioxide dissolves in water, it makes the liquid more acidic. Many kinds of plankton – the microorganisms that form the basis of global marine food webs – are essentially being dissolved by the ocean's increasingly acidic waters. More acidic seawater makes it harder for calcifying organisms such as plankton and coral to build and maintain their shells, skeletons, and other calcium carbonate structures; very acidic waters can even dissolve them. Greenhouse gas emissions from human activities – namely, using fossil fuels to power nearly every aspect of our lives, and emissions from agriculture – have driven rapid and large-scale changes within a few decades. "When history repeats itself eleven times, it is no longer a coincidence. It is a call to act," says UN Secretary-General António Guterres. "In this age of war, climate stress is also exposing another truth: our addiction to fossil fuels is destabilizing both the climate and global security," he adds. "Today's report should come with a warning label: climate chaos is accelerating and delay is deadly." Related: Climate Change Could Wipe 40% Off Global Economy, Study Predicts The report is based on data and input from national meteorological and hydrological services around the world, WMO Regional Climate Centers, United Nations partners, and dozens of experts. The World Meteorological Organization's State of the Global Climate 2025 report is available in full here.
Author: Jess Cockerill.
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