Copernicus says September 2026 was second warmest on record as El Niño strengthens

Global temperatures remained locked above a critical climate threshold in September 2026, according to the European Union's Copernicus Climate Change Service. The month ranked as the second warmest September ever recorded, and it marked the second consecutive month with global average surface air temperatures more than 1.5 degrees Celsius above the pre-industrial level. That back-to-back run is the first since November 2025, a signal that the planet is entering a new stretch of exceptional warmth.

The Copernicus Climate Change Service (C3S), which is implemented by the European Centre for Medium-Range Weather Forecasts (ECMWF), published its monthly climate bulletin on October 12, 2026. The data show that the global average surface air temperature for September was 16.27 degrees Celsius. That was 0.82 degrees Celsius above the 1991 to 2020 average, making it the second warmest September in the ERA5 dataset and 0.11 degrees Celsius cooler than September 2023. Relative to the estimated pre-industrial average of 1850 to 1900, September 2026 was 1.63 degrees Celsius warmer.

The ocean played a central role in the month's record heat. The September average sea surface temperature for the zone between 60 degrees south and 60 degrees north was the highest on record for the month, reaching 21.05 degrees Celsius and surpassing the previous September record of 20.92 degrees Celsius set in 2023. In the equatorial Pacific, El Niño conditions continued to strengthen, and the monthly Niño 3.4 sea surface temperature hit an all-time high of 29.70 degrees Celsius, exceeding the peak values of the very strong El Niño events of 1982/1983, 1997/1998 and 2015/2016.

Europe felt the heat and the dryness. The continent's land surface averaged 16.26 degrees Celsius in September, 1.54 degrees Celsius above the 1991 to 2020 average, making it the third warmest September on record for Europe. Western Europe tied its warmest September on record, matching 2023 at 2.51 degrees Celsius above average. The largest anomalies appeared over southern France, Portugal, Spain and parts of Italy, where temperatures climbed 4 to 6 degrees Celsius above average.

Key Facts

Copernicus reported on October 12 that September 2026 was the second warmest September ever recorded globally. The service put the global average surface air temperature at 16.27 degrees Celsius, which is 1.63 degrees Celsius above the pre-industrial level. The month was the second consecutive month above 1.5 degrees Celsius, following August 2026. The previous such run ended in November 2025.

The National Oceanic and Atmospheric Administration's National Centers for Environmental Information reported on October 9 that September 2026 ranked as the second warmest September in its 1850 to 2026 record, trailing only 2023. NOAA measured the global surface temperature at 2.39 degrees Fahrenheit (1.33 degrees Celsius) above the 20th century average. It was the 51st consecutive September above the 20th century average, and all 10 of the warmest Septembers on record have occurred since 2015. NOAA also reported on October 9 that September 2026 marked the fourth consecutive month with record warm global oceans. The global ocean surface temperature departure averaged 1.98 degrees Fahrenheit (1.10 degrees Celsius) above average, the highest ocean temperature departure for any month on record, beating August 2026 by 0.04 degrees Fahrenheit. Global land surface temperature averaged 3.29 degrees Fahrenheit (1.83 degrees Celsius) above average, third highest for September in the 177 year record.

Sea ice remained far below average. NOAA said global sea ice extent was the third smallest for September in the 48 year record at 8.54 million square miles, which is 800,000 square miles below the 1991 to 2020 average. The Antarctic had its third smallest September extent, and Copernicus noted that around Antarctica the sea ice extent reached its third lowest annual winter maximum.

Other records fell across regions and basins. NOAA reported that September 2026 was the warmest September on record for the Arctic region, North America and Asia. Europe had its fourth warmest September in NOAA's analysis and South America its sixth warmest. The Eastern North Pacific tied its September record for total tropical storms and set new basin records for both the number of hurricanes and major hurricanes. Globally, nineteen tropical cyclones formed during September.

EU Space, in its Copernicus image of the day published on October 12, reported that western Europe tied as the warmest September on record and that the continent as a whole had its third warmest September. The Emirates News Agency reported on October 12 that Carlo Buontempo, director of the Copernicus Climate Change Service, warned that global temperatures are likely to remain above 1.5 degrees Celsius over pre-industrial levels into 2027. Buontempo said: 'September was the second warmest on record globally, with exceptionally high temperatures experienced again across parts of Europe after an extreme summer. Crossing the Paris Agreement's long-term limit is only a matter of time.'

Analysis

The bigger picture here is that the world is no longer treating 1.5 degrees Celsius as a rare ceiling but as a recurring marker. Now, September 2026 is the second straight month above that line, and Copernicus expects the run to continue into 2027. The driver is not a mystery: a strengthening El Niño is adding heat to an atmosphere already loaded with greenhouse gases. The Niño 3.4 index at 29.70 degrees Celsius is higher than the peaks of the three strongest El Niño events of the past four decades.

What this really means is that the short-term record is being rewritten month after month, and the long-term trend is not reversing. NOAA's finding that all 10 of the warmest Septembers have occurred since 2015 is a clear sign of a shifting baseline. The fact that September 2026 was slightly cooler than September 2023 does not contradict that trend. It simply shows that natural variability can modulate the pace, while the underlying direction remains upward.

The regional impacts are already visible. In Europe, the combination of heat and drought produced record low September river flows on the Rhine, Danube, Vistula and Garonne-Dordogne. Those rivers are commercial arteries. When navigation slows and water supply tightens, the economic costs ripple through agriculture, energy and transport. The 4 to 6 degrees Celsius anomalies over southern France, Portugal, Spain and Italy are not just numbers on a map. They represent prolonged heat stress on crops, forests and populations, arriving after an extreme summer.

The ocean records add another layer of concern. The fourth consecutive month of record warm global oceans, with a departure of 1.98 degrees Fahrenheit (1.10 degrees Celsius), is unprecedented in NOAA's record. Warm oceans can supercharge tropical cyclones, and the Eastern North Pacific already set basin records for hurricanes and major hurricanes in September. The global count of nineteen tropical cyclones in September shows that the tropics remained active.

Why It Matters

The 1.5 degrees Celsius threshold is the more ambitious goal of the Paris Agreement. Scientists have long said that every fraction of a degree increases the risk of extreme heat, heavy rainfall, drought and sea level rise. Two consecutive months above that level do not formally breach the agreement's long-term limit. But they show how often the world is now touching that limit. Copernicus director Carlo Buontempo said that crossing the Paris Agreement's long-term limit is only a matter of time.

The persistence of the warmth into 2027 matters for planning. If El Niño remains strong, as Copernicus expects, then the coming year could bring more heat records, more marine heatwaves and more disruption to water systems. The record low river flows in Europe are an early example. Farmers, city planners, insurers and emergency managers need to prepare for conditions that were once considered extreme but are becoming more frequent. The data from Copernicus and NOAA are a warning that the climate system is carrying more energy, and that energy has to go somewhere.

The global picture also matters for the annual temperature ranking. NOAA said it is very likely that 2026 will rank among the five warmest years on record, and most likely second warmest. Year to date, the January to September global surface temperature was the second highest on record behind 2024. That puts 2026 on track to continue the string of exceptionally warm years that began in 2015.

Next Up

Copernicus and NOAA will publish their next monthly climate bulletins in November 2026, covering October. Those reports will show whether the run of months above 1.5 degrees Celsius extends to a third month and whether the record warm ocean temperatures persist. The evolution of the Niño 3.4 index will be a key indicator. If the index remains near its all-time high of 29.70 degrees Celsius, the odds of continued global warmth rise.

The longer-term question is whether 2027 becomes the year that the back-to-back 1.5 degrees Celsius months become a longer streak. Copernicus expects the run to continue into 2027. For now, the September data provide the clearest evidence yet that the world is in a new phase of sustained heat, driven by a record strength El Niño on top of a warming climate. The next few monthly bulletins will show how long this phase lasts.