The temperature of all oceans – excluding polar zones – reached 21.05°C worldwide in September, the highest level ever recorded for this month, surpassing the previous monthly record of September 2023 (20.92°C).
Surface temperatures “remained exceptionally high over a large part of the tropical Pacific, where El Niño conditions are strengthening and expected to further intensify in the coming months,” notes Copernicus in its monthly bulletin.
El Niño is a natural climate variation that warms surface temperatures in the central and eastern equatorial Pacific Ocean. The current episode, declared in June, could become the most intense on record, amplifying the effects of human-caused climate change.
Absolute record in September
Sea surface heat in the “Niño 3.4 region,” a reference zone in the Pacific, reached an all-time high of 29.70°C in September. This exceeds the maximum values of previous very powerful El Niño episodes in 1982/1983, 1997/1998 and 2015/2016, underlining, according to experts, the “exceptional intensity” of the current episode.
The Japan Meteorological Agency (JMA) announced on Friday that El Niño had intensified with sea temperatures 4.0°C above normal in the Pacific reference area, surpassing the previous record from December 1997.
But “we cannot yet say that the current El Niño episode is the strongest ever recorded,” Copernicus told AFP.
Climatologists are indeed trying to isolate the effect of El Niño from the underlying trend towards warming of the oceans in the context of climate change. Applying this criterion, the current episode has not yet exceeded in intensity the most significant episodes of the past.
El Niño can usually cause a rise in global temperatures the year following its peak intensity, expected in December according to the World Meteorological Organization (WMO).
Towards an even hotter year 2027?
However, for Carlo Buontempo, director of the Copernicus service, the average temperature on the surface of the globe as a whole could reach an unprecedented level as early as 2026. “If we follow the pattern observed in the past, we could experience a record year 2026, followed by a record year 2027,” he told AFP.
According to Copernicus, last month was the second warmest September on record, registering 1.63°C above pre-industrial levels, before the massive use of fossil fuels permanently warmed the climate.
This is the second consecutive month that temperatures have exceeded the threshold of 1.5°C of warming compared to this period, a limit which marks the most ambitious objective of the Paris Agreement.
Ten years ago, the latter’s ambition was to limit warming to well below 2°C and to continue efforts to contain it to 1.5°C.
This threshold has not yet been officially crossed, since it is understood on average over many years. But its overrun is now considered inevitable by most scientists and the UN, who are urging us to limit its scale and duration.
River flows at their lowest
The drought also continued in part of Europe, after an already very dry summer, and these conditions intensified or extended to the Iberian Peninsula, France, Italy, the western part of the Balkans and Greece, notes Copernicus.
As a result, “exceptionally low river flows persisted across much of Europe in September.” A situation which has made navigation almost impossible on certain parts of the Rhine in Germany.
