Decade of Fire: Earth just lived through its hottest 11 years, WMO warns

Hot on the heels of a scorching decade, the UN’s weather agency has said that the planet’s climate is “more out of balance than at any time in observed history”.

“Between 2015 and 2025, we experienced the hottest 11 years on record,” WMO’s deputy executive secretary Ko Barrett said.

Last year was some 1.43 °C above the 1850 to 1900 baseline in addition to breaking an ocean heat record, she explained.

Grim state of climate

Presenting a grim overview of the state of the climate in 2025, Barrett stressed that as glaciers continue to retreat and ice continues to melt, “the warming ocean and melting land-based ice are driving the long-term rise in global mean sea level rise.”

She said that the findings are an inspiration “to work harder to get lifesaving forecasts and early warnings into the hands of those who can protect lives and livelihoods” so that they can mitigate the devastating impacts of the ongoing climate turmoil on the most vulnerable.

For its part, WMO has been issuing annual climate updates for more than 30 years, and the record figures in the last decade have been an increasing cause for concern.

Record greenhouse gas levels

The agency’s scientific officer John Kennedy said that concentrations in the atmosphere of three key greenhouse gases (carbon dioxide, methane and nitrous oxide) reached record levels in 2024, the last year for which there are consolidated global numbers.

This marked the single-largest year-on-year increase.

“Data from individual sites around the world indicates that levels of these greenhouse gases continue to increase in 2025” and to modify “the energy balance of the planet”, he added.

Worrying energy imbalance

 Kennedy explained that under a balanced system, incoming energy from the sun is about the same as the amount of outgoing energy, but this is not the case at present.

“There’s less outgoing energy due to the increased concentrations of greenhouse gases,” he said. “More energy coming in than going out means that energy is accumulating in the Earth’s system.”

The Earth’s energy imbalance is a new indicator WMO has started tracking, with results pointing to a notable acceleration in the rate at which warming has been progressing between 2001 and 2025.

“The largest fraction of that absorbed energy is going to the oceans, around 90 per cent of the excess energy in the climate system,” Kennedy said. “This matters because over three billion people depend on these marine and coastal resources for their livelihoods. They’re living off the ocean, and nearly 11 per cent of the global population live on low-lying coasts directly exposed to coastal hazards.”