World Meteorological Organization Declares 2025 Among Hottest Years

Climate Change and Global Temperature Trends

By Kate Abnett

BRUSSELS, Jan 14 (Reuters) - Last year was among the planet's three warmest on record, the World Meteorological Organization said on Wednesday, as EU scientists also confirmed average temperatures have now exceeded 1.5 degrees Celsius of global warming for the longest since records began.

The WMO, which consolidates eight climate datasets from around the world, said six of them - including the European Union's European Centre for Medium-Range Weather Forecasts (ECMWF) and the British national weather service - had ranked 2025 as the third warmest, while two placed it as the second warmest in the 176-year record.

Impact of Exceeding 1.5 C

All eight datasets confirmed that the last three years were the planet's three hottest since records began, the WMO said. The warmest year on record was 2024. 

THREE-YEAR PERIOD ABOVE 1.5 C AVERAGE WARMING LEVEL

Political Response to Climate Science

The slight differences in the datasets' rankings reflect their different methodologies and types of measurements - which include satellite data and readings from weather stations.

ECMWF said 2025 also rounded out the first three-year period in which the average global temperature was 1.5 C above the pre-industrial era - the limit beyond which scientists expect global warming will unleash severe impacts, some of them irreversible.

"1.5 C is not a cliff edge. However, we know that every fraction of a degree matters, particularly for worsening extreme weather events," said Samantha Burgess, strategic lead for climate at ECMWF. 

Burgess said she expected 2026 to be among the planet's five warmest years.

CHOICE OF HOW TO MANAGE TEMPERATURE OVERSHOOT

Governments pledged under the 2015 Paris Agreement to try to avoid exceeding 1.5 C of global warming, measured as a decades-long average temperature compared with pre-industrial temperatures.

But their failure to reduce greenhouse gas emissions means that target could now be breached before 2030 - a decade earlier than had been predicted when the Paris accord was signed in 2015, ECMWF said.

"We are bound to pass it," said Carlo Buontempo, director of the EU's Copernicus Climate Change Service. "The choice we now have is how to best manage the inevitable overshoot and its consequences on societies and natural systems."

Currently, the world's long-term warming level is about 1.4 C above the pre-industrial era, ECMWF said. Measured on a short-term basis, average annual temperatures breached 1.5 C for the first time in 2024.

EXTREME WEATHER

Consequences of Extreme Weather

Exceeding the long-term 1.5 C limit would lead to more extreme and widespread impacts, including hotter and longer heatwaves, and more powerful storms and floods.

Already in 2025, wildfires in Europe produced the highest total emissions on record, while scientific studies confirmed specific weather events were made worse by climate change, including Hurricane Melissa in the Caribbean and monsoon rains in Pakistan which killed more than 1,000 people in floods.

Despite these worsening impacts, climate science is facing political pushback. U.S. President Donald Trump, who has called climate change "the greatest con job", last week withdrew from dozens of U.N. entities including the scientific Intergovernmental Panel on Climate Change.

The long-established consensus among the world's scientists is that climate change is real, mostly caused by humans, and getting worse. Its main cause is greenhouse gas emissions from burning fossil fuels like coal, oil and gas, which trap heat in the atmosphere.

(Reporting by Kate Abnett; Additional reporting by William James and Emma Farge; Editing by Alison Williams)