October 2025 may only rank “third-warmest” on paper, but that ranking is misleadingly calm. According to the EU’s Copernicus Climate Change Service, global average surface air temperature reached 15.14°C in October, about 0.70°C above the 1991–2020 normal for that month and roughly 1.55°C warmer than the late 1800s surface air temperature analysis and C3S news release. Over the last 12 months, from November 2024 through October 2025, the planet has hovered around 1.5°C of warming – the Paris Agreement’s most ambitious limit – making it the first time a full year-long period has sat at that level C3S data reported here. Climate monitors say 2025 is now virtually guaranteed to end among the three hottest years on record, likely just behind 2024 and possibly tied with 2023 2025 warmest-years assessment.

In other words, we are no longer talking about an isolated “hot year” pushed up by natural variations. The last three years form a sustained heatwave at the scale of the entire planet. UN and World Meteorological Organization experts describe 2023–2025 as a “triple whammy” of record-breaking warmth that risks “irreversible damage” to glaciers, sea ice and ecosystems if emissions do not fall rapidly UN/WMO overview. Their latest assessments underline that the 11 years since 2015 are the warmest in at least 176 years of records, and that the chances of keeping long-term warming below 1.5°C without overshooting are rapidly shrinking WMO data summary.

What makes October 2025 especially alarming is that this heat is arriving even as the Pacific has shifted out of the powerful El Niño that helped drive the record-shattering warmth of 2023–2024. NOAA’s Climate Prediction Center reports that the climate system is now in a La Niña state—a phase that usually brings slightly cooler global temperatures—yet the planet remains near record warmth ENSO Diagnostic Discussion. In its October update, NOAA said La Niña conditions are expected to persist through the Northern Hemisphere winter, with a transition back to “ENSO-neutral” most likely between January and March 2026 ENSO evolution and forecast PDF.

Independent forecasts from Columbia University’s International Research Institute for Climate and Society point in the same direction. Their October ENSO forecast shows a strong probability of La Niña lasting through the 2025–26 winter before easing, with early signs that the Pacific could warm again toward borderline El Niño conditions by mid-2026 current ENSO forecast. Taken together, these outlooks mean that even during a “cooling” phase of the Pacific cycle, human-driven greenhouse gas pollution is now keeping global average temperatures perilously high. What used to be a cooling breather in the climate system has become a barely noticeable dip on an otherwise steep curve.

The polar regions send an equally stark warning. Copernicus reports that Arctic sea ice extent in October 2025 averaged about 6.8 million square kilometres – roughly 12% below the 1991–2020 average and the eighth-lowest October in the entire 47-year satellite record Copernicus sea-ice cover and C3S summary post. In the Antarctic, October sea ice extent was about 6% below average, the third-lowest for the month on record C3S data reported here. Less sea ice means that more dark ocean absorbs sunlight instead of reflecting it, amplifying warming and disrupting ocean circulation—changes that can reverberate far beyond the poles.

Even more unnerving, both poles experienced record October warmth at the same time. Climate scientist Zack Labe notes that October 2025 saw the warmest October temperatures across both the Arctic Circle and the Antarctic Circle in the satellite era—an extremely unusual double record that signals how quickly the cryosphere is changing Zack Labe commentary. When the coldest parts of our planet repeatedly smash heat records, it accelerates ice loss, raises sea levels and destabilizes weather patterns far into the mid-latitudes where billions of people live.

On top of the background warmth, individual heat extremes in October 2025 were brutal. According to weather historian Maximiliano Herrera, who maintains one of the world’s most detailed archives of temperature records, the month saw temperatures as high as 46.7°C in Shabankareh, Iran, and 46.1°C in Birdsville, Australia, while parts of Greenland plunged to −50°C and Antarctica to below −67°C during the same period. Major weather stations in Mexico and Australia broke their all-time heat records for any October—yet not a single station with at least 40 years of data set an all-time cold record. Herrera’s logs for 2025 show at least nine countries or territories breaking or tying their national heat record this year, alongside roughly 78 monthly national or territorial heat records by the end of October, with only one monthly national cold record observed. This dramatic imbalance between heat and cold extremes is a clear fingerprint of a warming world, consistent with similar patterns documented in recent years background on Herrera’s record tracking and earlier analyses of unprecedented heat records.

The big picture is that the planet is not just creeping warmer; it is jumping into new territory. Copernicus notes that global sea surface temperatures between 60°N and 60°S remained close to record highs in October, averaging around 20.54°C—the third-highest for the month—driven in part by extreme warmth in the North Pacific C3S data reported here. At the same time, atmospheric concentrations of carbon dioxide continue to break records, recently reaching around 424 parts per million, compared with about 280 ppm before the industrial era CO₂ levels and warming overview. Every fraction of a degree added on top of this already dangerous baseline makes heatwaves, floods, droughts and storms more destructive.

Scientists stress that this run of record years is not inevitable fate but the direct result of policy choices. The physics are clear: as long as humans keep burning coal, oil and gas and destroying carbon-storing ecosystems, temperatures will keep rising, ice will keep melting and extreme weather will intensify. The same physics also give us a way out. Rapid cuts in fossil fuel use, massive expansion of renewables and efficiency, protection and restoration of forests and wetlands, and support for cleaner technologies can still bend the curve and limit future warming.

But the window is closing fast. The fact that the world is brushing up against 1.5°C of warming for an entire year, even as a La Niña begins to cool the Pacific, is a flashing red warning light for governments heading into upcoming climate negotiations. October 2025’s “third-warmest on record” label should not comfort anyone. It should be read as a siren: we are already living in a climate that is hotter, more unstable and more dangerous than the one our societies were built for—and without immediate, large-scale action to cut emissions and adapt, the records of 2023–2025 may soon look like the new normal rather than an exception.