The planet continues to warm and September 2025 confirms this: according to data from the Copernicus Climate Change Service (C3S), the month just ended was the third warmest September ever recorded globally. Surface air reached an average temperature of 16.11°C, which is 0.66°C above the 1991–2020 average and 1.47°C above pre-industrial levels.
The result comes from the European service managed by the ECMWF (European Center for Medium-Range Weather Forecasts) as part of the Copernicus programme, funded by the European Union. The data is based on ERA5 reanalysis, which processes billions of measurements from satellites, ships, planes and weather stations around the world.
“Land and sea temperatures remain persistently high, reflecting the ongoing influence of greenhouse gases in the atmosphere,” said Samantha Burgess, ECMWF Strategic Climate Officer.
A Planet that doesn’t cool down
Although slightly lower than the records of 2023 and 2024, September 2025 confirms a non-reassuring trend: the average global temperature of the last twelve months (October 2024 – September 2025) was 1.51 °C higher than the pre-industrial level. A value that exceeds the threshold of 1.5 °C indicated by the Paris Agreement as a limit not to be exceeded to avoid irreversible climate consequences.
Europe boiling (and under water)
In Europe, the average temperature in September was 15.95°C, 1.23°C above normal, placing it fifth in the hottest ever ranking. The largest anomalies were recorded in Fennoscandia (northern European region) and Eastern Europe, while a slight cooling was observed in some areas of Western Europe.
On the rainfall front, the month was marked by heavy rain and floods in several European countries, including Italy, Croatia and eastern Spain, while large areas of the Iberian Peninsula and the Balkans experienced drier than normal conditions.
Ever warmer seas
The global average sea surface temperature hit 20.72°C, the third highest value on record for September. In the Mediterranean, the waters were much warmer than average, particularly in the western and central areas. The marine anomaly is not just a statistical fact: it directly affects the climate and the frequency of extreme events, favoring heat waves, hurricanes and violent rainfall.
Sea ice continues to retreat
Satellite records show the Arctic recorded its 14th lowest annual minimum ice extent, a 12% decline from average. Antarctica also continues to lose ice, with monthly ice extent 5% less than normal. Data that signals a double collapse of the poles, increasingly vulnerable to global warming.
What the numbers tell us
The thermal and hydrological anomalies of September confirm that the Earth’s climate system is in a phase of persistent overheating, aggravated by the record concentration of greenhouse gases. At a regional level, drought and floods alternate, clear signs of a compromised balance.
Behind these data there is a clear signal: the global climate seems to have exceeded a critical threshold. Even without the influence of El Niño, temperatures remain very high, a sign that warming caused by greenhouse gases is now acting on its own. The oceans, which until now had absorbed some of the excess heat, are returning energy to the atmosphere. It is as if the Earth had stopped “cooling”, and its climate system was seeking a new equilibrium, warmer and more unstable.
