The ongoing La Niña event that contributed to floods in eastern Australia and exacerbated the drought in the United States and East Africa is likely to continue into 2023, according to recent forecasts. The occurrence of two consecutive La Niña winters in the Northern Hemisphere is common, but having three in a row is rare. The ‘trip dip’ La Niña – which lasted three years in a row – has only happened twice since 1950.
The long La Niña is likely to be a random meteor shower, scientists say. But some researchers warn that climate change could cause conditions like La Niña to worsen in the future. Matthew England, maritime biologist at the University of New South Wales in Sydney, Australia, states: “The potential for the next three events is increasing. England and others are now working to reconcile the tensions between weather data and the emergence of major meteorological species – efforts that could determine what awaits the planet.
Additional events in La Niña will increase the risk of floods in Southeast Asia, increase the risk of droughts and wildfires in the southwestern United States, and create a different pattern for hurricanes, hurricanes and tornadoes across the Pacific and Atlantic oceans, and provide growth. in other regional changes.
La Niña and its counterpart, El Niño, are El Niño – Southern Oscillation (ENSO) phases that occur every two to seven years, with neutral years in between. During El Niño events, typical Pacific winds blowing eastward westward near the equator weakening or receding, causing warmer waters to flow east of the Pacific Ocean, increasing rainfall in the region. During La Niña, those winds are blowing, the water is warm to the west and the east Pacific is cool and dry.
The effects are far-reaching. “The tropical Pacific is huge. When you change its rainfall, it has a devastating effect on the world, ”said Michelle L’Heureux, a natural scientist at the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center in College Park, Maryland. During La Niña years, the oceans absorb heat from its depths, so temperatures around the globe are often quite cold.
Cold snap
The current La Niña began about September 2020 and was soft to medium most of the time since then. Beginning in April 2022, tensions were high, leading to cold temperatures in the eastern Pacific Ocean that had not been observed at that time of year since 1950. England states: “That is incredible. June, gives 50–60% chance for La Niña to continue until July or September. This is likely to increase the activity of the Atlantic hurricane, which hit eastern North America until November, and reduce the season of the Pacific hurricane, which affects Mexico considerably. NOAA’s Climate Prediction Center predicted a 51% chance for La Niña by early 2023.
Ironically, L’Heureux reports, that this expanded La Niña, unlike the previous three immersions, did not follow the powerful El Niño, which often creates high seaside temperatures that last a year or two. “I always wonder, where is the dynamics of this?” says L’Heureux.The big questions left are whether climate change is changing ENSO, and whether La Niña conditions will prevail in the future.
Researchers have noted ENSO changes in recent decades and a recent report by the Intergovernmental Panel on Climate Change (IPCC) shows that strong El Niño and La Niña events have been more frequent and intense since 1950 than they were centuries ago. , but the panel could not determine whether this was due to environmental change or climate change. All in all, IPCC models show a shift in states such as El Niño as climate change warms the ocean, says Richard Seager, a climate coordinator at the Lamont – Doherty Earth Observatory of Columbia University in Palisades, New York. Ironically, Seager says, the observations showed the opposite during the last half century: as the climate warmed, the rising water tongue in the eastern hemisphere of the Pacific Ocean remained cold, creating conditions like La Niña2.
Some researchers argue that the record is too small to clearly represent what is happening, or that there is too much natural diversity in the system for researchers to see long-term trends. But it is also possible that IPCC models are missing something big, says L’Heureux, “which is a very serious problem”. Seager thinks that the models are wrong, and that the planet will have patterns similar to La Niña in the future3. “More and more people are taking this seriously as perhaps biased models,” because they do not have access to the cold eastern Pacific water, Seager said.
Cold water injection
England has another possible explanation as to why IPCC models could make future La Niña-like conditions worse. As the earth warms and the Greenland ice melts, its clear, fresh water is expected to slow down the ocean-going wave: the Atlantic Meridional Overturning Circulation (AMOC). Scientists strongly agree that the current AMOC has declined in recent decades4, but they do not agree on why, or it will slow down in the future.
England and its partners are showing how the collapse of the AMOC will leave extreme heat in the tropical South Atlantic, which could lead to a series of air pressure changes that ultimately strengthen Pacific business winds. These winds push the warm water to the west, thus creating conditions like La Niña. But England says current IPCC models do not reflect this practice because it does not involve complex interactions between ice-sheet melting, injections of fresh water, ocean currents and atmospheric circulation. “We have been adding instruments and whistles to these genres. But we need to install ice sheets,” he said. Michael Mann, a meteorologist at Pennsylvania State University at State College, also argued that the weather Getting the models to better reflect what’s going on in the ocean, says Seager, “remains a very active research topic”.
Source Journal Reference :Nicola Jones, Rare ‘triple’ La Niña climate event looks likely — what does the future hold?, Nature News (2022), doi: https://doi.org/10.1038/d41586-022-01668-1
