Update on the developing El Niño

This year's El Niño is still developing but it is already one of the most intense on record. El Niño events typically reach their peak around December* and this one might be the most powerful ever recorded if the early onset and strength are an indication. The event will alter weather patterns around the globe and boost global temperatures that were already rising due to climate change.

The strength of an El Niño event is measured by sea surface temperatures in a rectangular zone of the Pacific off the west coast of South America. Already this year, well ahead of the expected December peak, the measured temperatures are 2.6C above the average for this time of year (see graph below). There has never been such a strong El Niño recorded this early in the season.

This warming is happening in an ocean that has been heating up for decades as it absorbs heat trapped by greenhouse gas emissions from human activity. The effects are not constrained to the Pacific. On Saturday, the daily global average sea surface temperature reached 21.1 degrees Celsius , according to Europe’s Copernicus Climate Change Service, breaking the previous record set in March 2024.

* The name "El Niño" refers to the Christ child because of it's appearance around Christmas.

According to BOM, The El Niño is expected to persist into autumn 2027.  But El Niño is not the only ocean temperature anomaly that affects weather in Australia. The Indian Ocean Dipole (IOD) measures the difference in sea surface temperatures between the western and eastern tropical Indian Ocean. The IOD is currently neutral, but models suggest a positive IOD will develop which often brings reduced rainfall and higher temperatures to central and southern Australia during winter and spring. This may amplify the effects of the strong El Niño.

Long range forecasts from BOM are shown below which take into account the both the developing El .Niño and the predicted positive IOD.