September 2026 second warmest on record, global temperatures exceed: C3S

September 2026 was exceptionally warm worldwide. C3S measured the global average surface air temperature at 1.63°C above the estimated pre-industrial level. That made the month the second-warmest September in the global record. The result matters because it extends a run of unusually hot months and shows how close the planet remains to, and sometimes exceeds, major climate thresholds.

The month also set a separate ocean record. Average sea-surface temperature across extra-polar oceans, between 60°S and 60°N, reached 21.05°C. This surpassed the previous September record of 20.92°C, set in 2023. Strengthening El Niño conditions were occurring at the same time.

September did not hold the overall September air-temperature record, because another September was warmer. However, it was the second consecutive month in 2026 above 1.5°C, following August, which was tied with July 2023 as the warmest month ever recorded globally. C3S expects the hot run to continue into 2027.

A pre-industrial level is a reference point for comparing modern global temperatures with the cooler climate that existed before large-scale industrial greenhouse-gas emissions. Scientists use an estimated average temperature from that earlier period as a baseline. The article does not specify the exact years used for its baseline, but calls it the estimated pre-industrial level.

The comparison is useful because it turns a complicated global temperature change into one understandable number. In September 2026, the global average surface air temperature was 1.63°C above that reference. This does not mean every place was exactly 1.63°C warmer. It is a global average across land and ocean measurements.

The baseline also helps explain climate targets. A month above 1.5°C is a short-term measurement against this reference. It is different from judging the planet’s longer-term warming level. C3S said September continued a new run of months above 1.5°C, while noting that the Paris Agreement limit concerns the long term.

A ranking compares September 2026 with every other September in the available global temperature record. C3S found that September 2026 was the second warmest, so at least one earlier September had a higher global average surface air temperature. The ranking refers specifically to September months, not to every month in history.

The article gives the temperature for September 2026 as 1.63°C above the estimated pre-industrial level. It also reports that August 2026 was the joint warmest month ever recorded globally, tied with July 2023, at 1.65°C above the same baseline. Those figures provide context, but they do not establish which September was warmer.

The article does identify a separate September record for the oceans. Extra-polar sea-surface temperature reached 21.05°C, beating the previous September ocean record of 20.92°C from 2023. Thus, September 2026 was second warmest for global air temperature but first for September extra-polar ocean temperature.

When a month exceeds 1.5°C, its global average temperature is more than 1.5°C above the estimated pre-industrial reference. September 2026 reached 1.63°C above that level. This is a monthly temperature result, so it captures conditions during one month rather than the planet’s settled, long-term warming state.

The Paris Agreement’s 1.5°C limit is assessed over a much longer period, generally using sustained global warming rather than one unusually hot month. Natural variability can temporarily push monthly temperatures above the threshold. El Niño is one influence that can add heat to a long-term warming trend. A single month therefore does not by itself prove that the long-term limit has been permanently crossed.

C3S said September was the second consecutive month above 1.5°C in 2026 and that the run may last into 2027. Carlo Buontempo said crossing the Paris Agreement’s long-term limit is only a matter of time, while the amount and duration of overshoot remain important.

El Niño is a recurring climate pattern involving unusually warm surface waters in the equatorial Pacific. Those ocean changes affect the atmosphere above them and alter the movement of heat and moisture around the world. The article reports that El Niño was strengthening in September 2026 and was likely to become one of the strongest events ever recorded.

Warm Pacific waters release more heat and moisture into the atmosphere. This can raise global average temperatures for a time, especially when it combines with the background warming caused by greenhouse gases. El Niño also shifts large-scale rainfall patterns. Some regions can receive more rain, while others become unusually dry.

The World Meteorological Organization said El Niño would continue intensifying and likely peak in December. It warned of above-average temperatures across much of the globe, changed rainfall patterns, and increased risks of drought and floods in different regions. C3S said the strengthening event could help keep the run of months above 1.5°C going into 2027.

Unusually warm oceans store and release more heat, influencing the atmosphere and weather systems. They can help raise global temperatures and support a stronger El Niño. Changing ocean conditions also affect rainfall patterns, which matters for water supplies, agriculture, ecosystems, and communities exposed to extreme weather.

The WMO said the strengthening El Niño could bring above-average temperatures to much of the world and shift rainfall. That combination can increase drought risk in some regions and flood risk in others. The article gives no regional examples, but it links the changing rainfall pattern to both hazards. The warmer ocean also set a September record, reaching 21.05°C across extra-polar waters.

Sea ice provides another indicator of unusual conditions. Around Antarctica, sea-ice extent reached its third-lowest annual winter maximum. The article reports this alongside the ocean record, but does not claim that one event alone caused the sea-ice result. Continued warming and a strong El Niño could bring further unusual conditions into 2027.

Greenhouse gases such as carbon dioxide and methane absorb some heat that Earth sends toward space and re-emit it. This slows the loss of heat, warming the atmosphere and surface. The oceans absorb much of the extra energy, so they warm too. This process builds over years and decades rather than lasting only for a season.

El Niño can temporarily add heat to global temperatures by shifting heat from the tropical Pacific into the atmosphere. Greenhouse-gas warming is different because it changes the underlying climate baseline. When an El Niño occurs on top of that baseline, its temporary warmth can produce especially high monthly or yearly temperatures. September 2026’s 1.63°C reading occurred during strengthening El Niño conditions.

The article focuses on records rather than explaining the greenhouse effect. It reports a second consecutive month above 1.5°C and expects the run to continue into 2027. Reducing greenhouse-gas emissions would limit additional long-term warming, while natural events such as El Niño would continue to cause shorter-term fluctuations.