The current El Niño phase of the Pacific Ocean is forecast to peak during the coming months as one of the strongest on record, laying the platform for unprecedented global temperatures through 2024.
A comparison of the most recent 17 El Niño events show the 2023 edition was the sixth strongest to October based off the most commonly used measure, the Niño 3.4 index.
Niño 3.4 is a calculation made by climatologists to measure the central Pacific sea surface temperature (SST) relative to average.
The value was analysed at +1.6 degrees Celsius in October, double the Bureau of Meteorology's (the Bureau) El Niño threshold and above the National Oceanic and Atmospheric Administration's (NOAAs) +1.5C criteria for a "strong" event.
Most forecasts indicate the Pacific should continue warming during the coming weeks and peak through December and January.
According to the latest NOAA monthly diagnostic report there is even a possibility this El Niño could rival previous super events, including the record strong El Niños of 1997/98 and 2015/16.
"There is a 35 per cent chance of this event becoming 'historically strong' (>2.0°C) for the November-January season," the report said.
A Niño 3.4 index exceeding 2.2C, which some models are predicting (including the Bureau's), would send the ranking into the top three strongest El Niño's since 1950.
The World Meteorological Organization (WMO) concurred with NOAA's intensity assessment, however both organisations have cautioned against drawing conclusions on the subsequent change in weather.
"A strong El Niño does not necessarily mean strong El Niño impacts locally … El Niño is not the only factor that drives global and regional climate patterns, and that the magnitudes of El Niño indicators do not directly correspond to the magnitudes of their effects," the WMO reported last week.
Hot summer for Australia and record hot 2024 possible
The complex relationship between El Niño and weather patterns is especially relevant to Australia where the rainfall impact diminishes during summer while temperatures remain unusually high.
This means that while Australia's rainfall should gradually shift to resemble a conventional summer pattern during the coming months, our temperatures are likely to remain well above average.
An additional influence on our upcoming summer temperatures is Earth's record warm seas, which according to the WMO's Global Seasonal Climate Update strongly favour ongoing warmth for Australia.
"Consistent with the anticipated development of an El Niño … together with the prediction of above-normal sea-surface temperatures over much of the global oceans, there is widespread prediction of above-normal temperatures over almost all land areas …. Over most other Southern Hemisphere land areas north of about 30º S, the probabilities for above-normal temperature are strongly increased."
Considering all factors, it would therefore be no surprise if this summer was close to Australia's hottest on record.
The WMO has also warned El Niño is likely to last until at least April and combine with climate change to bring further exceptionally high temperatures through 2024.
"El Niño impacts on global temperature typically play out in the year after its development …. 2023 is now on track to be the warmest year on record. Next year may be even warmer. This is clearly and unequivocally due to the contribution of the increasing concentrations of heat-trapping greenhouse gases from human activities," WMO Secretary-General Petteri Taalas said.
Indeed 2016, which until 2023 was the warmest year on record, saw global temperatures peak three months after El Niño's decay, and as the graph below depicts a similar trend in 2024 would lead to global temperatures reach 2C above pre-industrial levels (1.12C above 1991-2000 average) for the first time.
Indian Ocean Dipole (IOD) peaks as one of the strongest on record
It is not just the Pacific Ocean that meteorologists and climatologists are monitoring closely this year – the Indian Ocean is also in an anomalous state capable of impacting broadscale weather patterns.
A positive phase of the IOD formed in late winter, strengthened rapidly through September to reach an October apex surpassed only by the record positive IODs in 2019 and 1997.
When combined with El Niño the strong positive IOD helped drive the lowest Australian rainfall through the August to October quarter since at least 1900.
Thankfully, the alternating phases of the Indian Ocean, unlike El Niño and La Niña, do not linger through Australia's summer and the subsequent impact on our weather has completely faded by January.