El Niño weather pattern enters record territory — scientist

Zeke Hausfather, a climatologist at Berkeley Earth and co-author of comprehensive climate change reports for the United Nations, said that the sea surface temperature anomaly in the tropical Pacific now stands at 3.07C, which ties with the 2015-2016 El Niño.

"This month (September) is very likely to have the highest monthly anomalies on record, barring something quite unexpected in the coming week," he said in an email.

Hausfather's figures, published on the Climate Brink dashboard, draws on the National Oceanic and Atmospheric Administration (NOAA) satellite-and-buoy sea surface record.

They are based on how much daily sea surface temperatures in the Nino 3.4 region -- an imaginary box in the Pacific -- are above a 30-year-average.

But NOAA itself has shifted to a newer method called the Relative Oceanic Nino Index (RONI), which gauges warming in the Nino 3.4 region against warming across the whole tropical belt. The goal of this change is to account better for the impacts of climate change heating oceans in general.

On that metric, the numbers run lower, and the current El Niño is still below the record, though expected to eventually break it.

El Niño is the warming phase of a natural cycle in the tropical Pacific known as the El Niño-Southern Oscillation (ENSO).

It sets in when trade winds that blow from east to west temporarily ease up, allowing warm water which normally piles up in the western Pacific Ocean to slide back east and rise to the surface.

When those warmer-than-average surface temperatures last for a few months, they cause more storms and clouds over the region, which in turn cause ripple effects through the entire global atmosphere.

The upshot is hotter and drier conditions in some places, cooler and wetter in others.

Human-caused climate change can increase El Niño's impacts. A warmer atmosphere holds more moisture, so El Niño-linked rains can turn more extreme. It also dries out soil, deepening drought where El Nino brings it.

Scientists aren't in full agreement about whether climate change intensifies El Niños themselves, but a recent study based on coral skeletons found there had been "striking amplification" of El Niños in the past 40 years compared to the pre-industrial period.

This El Niño is already hitting some regions hard, including in Central America, where animals and crops are dying from drought. Lack of water also poses huge problems for the Panama Canal.

Five percent of global trade passes through the waterway linking the Atlantic and Pacific. It cannot function without the reservoir water it uses to power locks that lift and lower ships at the start and end of their passage, and authorities have had to slash traffic through the canal.

In Indonesia, it is blamed for drought that has fueled wildfires which have wrought havoc on the vast archipelago.