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The world recorded its third-warmest September this year, according to new data from the European Union’s Copernicus Climate Change Service (C3S).
Global temperatures averaged 16.11 degrees Celsius (60.9 degrees Fahrenheit), only 0.07 degrees Celsius cooler than in 2024 and 1.47 degrees Celsius above the pre-industrial average.
C3S Deputy Director Samantha Burgess said, “A year on, the global temperature context remains much the same, with persistently high land and sea surface temperatures reflecting the continuing influence of greenhouse gas accumulation in the atmosphere.”
From October 2024 to September 2025, global average temperatures were 1.51 degrees Celsius higher than in pre-industrial times, temporarily exceeding the 1.5 degrees Celsius threshold that the international community aims to avoid.
Although the limit is officially considered breached only when exceeded for several consecutive years, the latest data mark another warning that climate targets are slipping further out of reach.
According to C3S, September’s surface air temperatures were 0.66 degrees Celsius above the 1991–2020 average, showing the continuing impact of rising greenhouse gas levels from human activity, especially fossil fuel use.
The heat affected nearly every region. Europe recorded its fifth-warmest September, with temperatures 1.23 degrees Celsius above the 1991–2020 average.
Southwestern Europe endured particularly extreme conditions, with southern France, Spain and Portugal facing wildfires that forced thousands to evacuate.
Spain alone recorded over 1,100 heat-related deaths.
Unusual warmth also extended to Siberia, Antarctica, the Middle East, and parts of Asia, including China, Japan and the Korean Peninsula.
Japan experienced its hottest summer on record earlier this year, which scientists linked to a prolonged marine heatwave in the North Pacific.
Sea surface temperatures averaged 20.72 degrees Celsius globally in September, the third highest for the month since records began. “Much-above-average” heat was observed in the Mediterranean, North Pacific, and Arctic seas.
A persistent marine heatwave known as the “blob” has stretched about 5,000 miles (8,046.7 kilometers) from Japan to the U.S. West Coast since August, altering weather patterns and putting marine life at risk.
The world’s oceans absorb over 90% of excess heat caused by human-induced greenhouse gases and around a quarter of global carbon dioxide emissions.
As a result, scientists warn that marine ecosystems are facing severe stress, from coral bleaching to declining oxygen levels.
A 2019 Intergovernmental Panel on Climate Change (IPCC) report predicted that marine heatwaves will intensify with climate change, disrupting corals, fisheries, and coastal livelihoods.
Those warnings are already visible, as the world is now experiencing the largest mass coral bleaching event ever recorded, affecting dozens of countries worldwide.
Researchers stress that exceeding 1.5 degrees Celsius for long periods could trigger irreversible changes, including higher sea levels, stronger storms, longer heatwaves, and widespread ecosystem loss.
These trends, Copernicus experts say, underscore the urgency of reducing emissions and investing in adaptation.
“The global temperature context remains much the same,” Burgess said.
“Persistently high land and sea surface temperatures reflect the continuing influence of greenhouse gas accumulation in the atmosphere,” she added.
The data serve as another reminder that global warming is not slowing down.
Scientists say each record year reinforces the narrowing window to limit temperature rise and prevent the most damaging effects of the climate crisis.
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