Eastern Australia looks set for a drier winter and spring as a US federal agency predicts an “extremely high likelihood” of an El Niño developing later in the year.
According to the US Climate Prediction Center, a weak El Niño is likely and there is an 80% chance of a moderate El Niño in the next couple of months, with a greater than 90% chance it will persist into our summer.
The agency also forecasts about a 55% chance of a strong El Niño.
El Niño is the warm phase of the El Niño-Southern Oscillation (ENSO). It occurs when the sea surface temperatures rise at least 0.8C above the long term average in a part of the central and eastern tropical Pacific Ocean. Extreme El Niños feature temperatures in that region of 2C above average.
According to the latest ENSO Outlook from @NWSCPC, the El Niño Watch persists with El Niño likely to develop within the next couple of months and then persisting (> 90% chance) into the winter.
— NOAA Climate.gov (@NOAAClimate) May 11, 2023
More on that + our scorching oceans at the ENSO Blog.https://t.co/0RRmVKHQJr pic.twitter.com/CeHYn0ZRsE
In Australia, El Niño raises the risk of drought, heatwaves and bushfires in the east of the country and also increases the chances of mass coral bleaching of the Great Barrier Reef.
Nine of the 10 driest winter-to-spring periods for eastern Australia on record have been during El Niño years.
Experts have warned that strong vegetation growth as a result of the rare “triple-dip” La Niña, which persisted for three years from 2020 to 2022, could result in increased fuel for fires if conditions become drier and hotter.
El Niño years tend to be associated with higher global average temperatures in comparison to La Niña and ENSO-neutral years.
The strongest El Niño this century, in 2015-16, helped push global temperatures to the hottest ever recorded, and was linked to linked with outbreaks of infectious diseases including cholera and dengue fever.
According to Nat Johnson of the US National Oceanic and Atmospheric Administration, “given how warm the oceans are already, a developing El Niño would only increase the chance of record-breaking global ocean temperatures (and global average temperature over both ocean and land), which likely would have important ecological consequences, including for fish and corals”.
The Bureau of Meteorology’s latest ENSO forecast was issued on 9 May. “There is approximately a 50% chance of El Niño developing in 2023. This is about twice the normal likelihood,” it said at the time.
According to the BoM, seven models from international weather agencies all indicate that the thresholds for El Niño will be met by August.
During an El Niño, warmer sea surface temperatures in the central and eastern equatorial Pacific Ocean cause a weakening or even reversal of the equatorial trade winds that typically blow from east to west across the Pacific.
As a result, heavy rainfall that usually occurs in the western Pacific, to the north of Australia, shifts to the central and eastern Pacific basin.
Research has previously shown that the chances of experiencing extreme El Niño events will increase with continued anthropogenic global heating.
