The rare “triple dive” La Niña is over

Severe flooding in Brisbane, Australia in February 2022.

The Australian Bureau of Meteorology joined their US counterparts, the National Oceanographic Atmospheric Administration, on Tuesday morning in announcing the end of the natural La Niña climate pattern in the Pacific Ocean.

La Niña was responsible for bringing record rainfall to eastern Australia, above-average numbers of tropical cyclones in the Atlantic, and drought conditions to eastern Africa.

Meteorologists are now looking at El Niño for late 2023, which would have different consequences for weather patterns around the world.

La Niña is the phase of the El Niño Southern Oscillation (ENSO) model in which waters in the Pacific Ocean are colder than average, the opposite of the warmer El Niño phase.

ENSO would normally transition from La Niña to El Niño every two to five years, but in 2022 Pacific waters cooled for the third consecutive year bringing a rare La Nina “triple dip.”

The most severe impact of this La Niña period was in eastern Australia, which saw severe flooding and record-breaking rainfall in 2022.

In Sydney, the annual rainfall record was broken in October and 2577mm of rain fell by the end of the year, surpassing the previous record of 2244mm set in 1950.

Sydney sees wettest year on record

Evacuations as floods hit three Australian states

La Niña was also partially responsible for bringing a record-breaking Atlantic hurricane season in 2020 and the third most active season in 2021.

Sea surface temperatures in the eastern parts of the Pacific Ocean increased in February and early March, and now the Bureau of Meteorology (BOM) and the National Oceanographic Atmospheric Administration (NOAA) have declared ENSO to be “neutral”, so neither La Niña nor El Nino.

Forecasters predict that neutral conditions will persist through the Northern Hemisphere spring and early summer 2023.

Beyond that there are some predictions of a warming Pacific that will lead to El Niño developing by the end of the summer, so BOM has issued an “El Niño watch” which means there is a 50% chance that El Niño develops.

While El Niño Southern Oscillation forecasts in spring are more uncertain than any other time of year, it still provides a good indication of what we might expect later this year and into 2024.

Firefighters facing a fire

El Niño could lead to an increased risk of wildfires like this one in Sydney, New South Wales in December 2019.

What could El Nino bring?

The biggest impact of El Nino, particularly if it is strong, is on the global average temperature which can increase by 0.2°C more.

As the Pacific Ocean warms, this extra heat is released into the atmosphere much like a boiling pan of water gives off steam and raises the temperature in a kitchen.

The hottest year on record was 2016, when a strong El Niño raised global temperatures.

The influence a potential El Niño will have on global temperature in 2023 is likely to be minimal as it is only expected to start later this year.

However, as the Niña’s cooling phase has ended, the Met Office suggests temperatures will be between 1.08C and 1.32C above pre-industrial levels.

Met Office predicts 2023 will be hotter than 2022

Some of El Niño’s other impacts include drier and hotter weather in Australia that could lead to increased risks of bushfires, flooding in eastern areas of South America such as Peru and Ecuador, and drought in the Amazon region.

El Niño is also a factor that could reduce the development of Atlantic tropical cyclones, therefore leading to fewer hurricanes.

As to the influence of El Niño on the UK’s climate, this is more uncertain, but continuing research suggests this is a factor in the potentially colder winter weather.

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