UN chief warns of ‘climate chaos’ as WMO reports record heat and deepening planetary imbalance

"Climate chaos is rewriting the rules of weather,” UN Secretary-General António Guterres warned on World Meteorological Day, as new data confirmed accelerating global warming driven by record greenhouse gas levels.

Highlighting intensifying heat, prolonged droughts, rising seas and increasingly frequent extreme events, the UN chief stressed that “accurate, trusted science is our first line of defence,” underscoring the critical role of global observation systems and early warning services in saving lives.

His message comes as the World Meteorological Organization (WMO) reported that concentrations of greenhouse gases in the atmosphere have reached all-time highs, continuing to drive record temperatures across land and ocean with long-lasting consequences for humanity.

Climate system ‘more out of balance than ever’

Following the hottest decade on record, the UN’s weather agency said the planet’s climate is now “more out of balance than at any time in observed history.”

“Between 2015 and 2025, we experienced the hottest 11 years on record,” said Ko Barrett, WMO Deputy Executive Secretary.

Global temperatures in 2025 were around 1.43°C above the 1850–1900 baseline, she noted, alongside record-breaking ocean heat levels — a clear indication of the growing accumulation of energy within the Earth system.

Warming oceans, melting ice, rising seas

Presenting a stark overview of the state of the climate, Barrett warned that ongoing glacier retreat and ice loss are accelerating sea-level rise.

“The warming ocean and melting land-based ice are driving the long-term rise in global mean sea level,” she said.

She emphasized that the findings must spur stronger efforts to expand early warning systems and ensure that life-saving forecasts reach those most at risk, helping communities better withstand climate shocks.

WMO has issued annual climate assessments for more than 30 years, but recent record-breaking trends have become an increasing source of concern.

Greenhouse gases hit record highs

The agency also reported that concentrations of carbon dioxide, methane and nitrous oxide reached record levels in 2024 — the latest year with consolidated global data — marking the largest annual increase on record.

According to WMO scientific officer John Kennedy, preliminary observations show that levels continued to rise in 2025, further altering the planet’s energy balance.

A growing energy imbalance

In a stable climate system, incoming solar energy is balanced by outgoing radiation. But this equilibrium has been disrupted.

“With increased greenhouse gas concentrations, less energy escapes into space,” Kennedy explained. “More energy coming in than going out means that energy is accumulating in the Earth’s system.”

A new WMO indicator tracking Earth’s energy imbalance shows a marked acceleration in warming between 2001 and 2025.

Around 90 per cent of the excess heat is absorbed by the oceans — a development with major implications, as more than three billion people depend on marine and coastal resources for their livelihoods. Nearly 11 per cent of the global population lives in low-lying coastal areas directly exposed to climate-related hazards.

Call to strengthen global observation systems

Under this year’s theme, “Observing Today, Protecting Tomorrow,” the Secretary-General called for urgent investment in climate monitoring and early warning infrastructure.

He urged governments, development banks and the private sector to scale up support for the global observing system — from ground stations to satellites — and to ensure open and equitable data sharing.

Guterres also stressed the need to accelerate the Early Warnings for All initiative so that, by 2027, every person on Earth is protected by life-saving alerts.

“By observing today, we can protect tomorrow — for people, for planet, for prosperity, and for generations to come,” he said.