The chance that the ocean warming event known as El Niño will strike this year is now over 90%. It is likely to start in the coming months, and is very likely to persist until 2024 and have a widespread impact, experts warned.
El Niño, which means “the little boy” in Spanish, is a major weather event caused by changes in ocean currents in the Pacific Ocean. This warming event is strong enough to trigger major changes in global weather patterns and seriously impact marine ecosystems, especially combined with the effects of human activity. climate change. El Niño, along with its counterpart La Niña, or “the little girl,” a cooling event triggered by changes in the same ocean current system, make up the El Niño-Southern Oscillation (ENSO) cycle.
Experts have suspected that an El Niño event could be on the horizon for some time. And on May 3, the World Meteorological Organization (WMO) predicted that there was a 60% chance to start between May and July (opens in a new tab).
But on May 11, the National Oceanic and Atmospheric Administration (NOAA) released its own forecast, which suggested that El Niño will almost certainly begin during the same period. The agency also said there are there was a 90% chance that El Niño would persist until 2024 (opens in a new tab).
Related: Is climate change making the weather worse?
“Keep your eyes peeled in the tropics and don’t blink”, nathaniel johnson (opens in a new tab)a meteorologist at NOAA’s Geophysical Fluid Dynamics Laboratory, wrote in a NOAA Blog Post (opens in a new tab). “Conditions are rapidly evolving!”
ENSO cycle 101
The ENSO cycle is primarily related to the trade winds in the Pacific Ocean blowing west along the equator. Typically, this carries warmer surface water from South America to Asia, which in turn is replaced by cooler deep ocean water in a process known as upwelling, according to NOAA (opens in a new tab).
During El Niño, the trade winds weaken, leading to less upwelling and, in turn, warmer surface waters. During La Niña, the trade winds are unusually strong, which has the opposite effect. Both events can trigger extreme weather events, such as Cyclone Freddy, which could break records. battered parts of africa in february and march.
The periods between El Niño and La Niña events are known as ENSO neutral.
When was the last El Niño?
In the past, El Niño and La Niña events occurred about once every two to seven years, according to NOAA. But recently its appearance has become much more erratic due to the effects of climate change: In the last 50 years, the ocean has absorbed almost 90% of the energy trapped by global warmingwhich has dramatically increased sea surface temperatures, impacting the ENSO cycle.
The last El Niño event occurred between February and August 2019 and was quite weak. Between July 2020 and March 2023, a rare La Niña triple dive suppressed rising global temperatures.
El Niño events typically last between nine months and two years, but can be longer.
How strong will El Niño be?
It is not clear how strong this El Niño will become, but NOAA predictions suggest there is an 80% chance of at least a moderate El Niño, in which sea surface temperatures will rise 1 .8 degrees Fahrenheit (1 degree Celsius), and a 55% chance of a strong El Niño, where temperatures will rise 2.7 F (1.5 C).
Experts are also concerned that recent high sea surface temperatures will worsen the next El Niño event. In early April, the global mean sea surface temperature was highest in recorded history.
NOAA will provide more information on how El Niño is progressing in early June.
How will El Niño affect North America?
During El Niño, weaker trade winds mean more warm water is pushed east toward the west coast of the Americas. Warmer waters push the Pacific jet stream south of its neutral position, affecting weather patterns in North America, according to NOAA.
For the northern US and Canada, this can lead to warmer-than-usual weather, while eastern states typically receive less precipitation. For the southern US and northern Mexico, the result is often heavy rain, which can lead to flooding and mudslides.
The WMO expects global temperatures to rise to record levels over the next several years as the cooling effect of La Niña ends and El Niño begins, potentially severely affecting the lives of millions of people.