The rare “triple trough” La Niña is over

Severe flooding in Brisbane, Australia in February 2022.

Australia’s Bureau of Meteorology joined its US counterparts, the National Oceanographic Atmospheric Administration, on Tuesday morning to announce the end of the natural La Niña climate pattern in the Pacific Ocean.

La Niña brings record rainfall to eastern Australia, above-average numbers of tropical cyclones in the Atlantic and drought conditions in East Africa.

Forecasters are now on the lookout for El Niño for later in 2023, which would have different consequences for weather patterns around the world.

La Niña is the phase of the El Niño pattern of Southern Oscillation (ENSO) where the waters of the Pacific Ocean are colder than average, in contrast to the warmer phase of El Niño.

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

The most severe impact of this La Niña period has been in eastern Australia, which experienced severe flooding and record rainfall in 2022.

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

Sydney experiences wettest year on record

Evacuations as floods hit three Australian states

La Niña was also partly responsible for the record Atlantic hurricane season in 2020 and the third most active season in 2021.

During February and early March, the sea surface temperature in the eastern parts of the Pacific Ocean increased 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 Niño.

Forecasters expect neutral conditions to persist through the Northern Hemisphere spring and early summer of 2023.

Beyond that, there are predictions of a warming in the Pacific leading to the onset of El Niño by the end of the summer, so BOM has released an “El Niño watch”, which means there is a 50% chance of El Niño developing.

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

Firefighters dealing with a forest 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 Niño bring?

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

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

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

The influence that a potential El Niño will have on global temperature in 2023 is likely to be minimal, as it is not expected to begin until later this year.

However, as the cooling phase of La Niña is over, the Met Office suggests temperatures will be between 1.08C and 1.32C above pre-industrial levels.

The Met Office predicts 2023 will be warmer than 2022

Some of El Niño’s other impacts include drier and warmer weather in Australia potentially leading to greater wildfire risk, flooding in eastern regions of South America such as Peru and Ecuador, and drought in the Amazon region.

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

As for El Niño’s influence on UK weather, that’s more uncertain, but ongoing research suggests it’s a factor in a potentially colder winter.

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