There are increasing signs that an El Niño phenomenon is developing and could develop into a potentially severe event in the coming months, disrupting weather patterns around the world. El Niño (if timed right) could influence the Atlantic hurricane season and further accelerate global warming, making another record-warm year this year or next much more likely than it otherwise would be.
El Niño and La Niña are periodic climate cycles that occur every few years in the tropical Pacific Ocean and can have a significant impact on global weather patterns. These can cause flooding in parts of Africa and drought in others, winter storms on the west coast and, in the case of El Niño events, more heatwaves around the world.
El Niño is characterized by unusually warm ocean waters along the tropical Pacific Ocean near the equator and a series of changes in atmospheric wind and precipitation patterns. These changes are significant enough to affect weather around the world. Currently, abnormally warm seawater is spreading below the ocean surface from the western to eastern parts of the tropical Pacific Ocean, which may be a precursor to such a phenomenon.
Although there is still considerable uncertainty in the forecast, most forecasts from El Niño monitoring groups such as the United States and Australia indicate that the current weak La Niña event will weaken in the coming months. La Niña is El Niño’s cold-water sibling and can also cause global weather disruptions. For now, experts predict that so-called “ENSO neutral” conditions, in which neither La Niña nor El Niño will be present, will emerge in late spring and summer.
El Niño can then develop in late summer and fall, depending on a variety of factors, from the direction and strength of trade winds to the oscillation of warmer-than-average ocean waters across the western and eastern tropical Pacific Ocean.
Outlooks from the National Oceanic and Atmospheric Administration, the Australian Bureau of Meteorology and other groups all point to the same general scenario, but with varying degrees of confidence and slight differences in timing.
Although the oceans are now becoming more El Niño-like and are predicted to become even more El Niño-like, atmospheric circulation still reflects the effects of a weak La Niño event. This means that even if an El Niño event occurs, it will still take several months for its effects to be felt.
To predict El Niño events more reliably, the trade winds that blow from east to west across the equator need to weaken, allowing more warm water from the western Pacific Ocean to flow east to the surface. So far, this shift in trade winds has not been consistent, but computer models predict it will change in the coming months.
In fact, some computer models, including the well-regarded European Ensemble, make El Niño so aggressive that it develops into an intense “Super El Niño” event by late fall. If this happens, the Atlantic hurricane season could be sleepier than usual, as El Niño tends to be accompanied by stronger wind shear over the tropical Atlantic.
Wind shear occurs when winds blow at different speeds and directions depending on height, and acts as a barrier to a nascent tropical storm or hurricane.
El Niño years tend to increase the Earth’s average surface temperature, thereby setting heat records in concert with anthropogenic global warming. A strong El Niño, also known as a Super El Niño, would almost certainly push global temperatures into record territory, further accelerating warming and potentially leading to more coral bleaching and other harmful effects.
Forecasters have warned that El Niño forecasts tend to be less accurate during this period, known as the spring forecast barrier. One forecaster compared this barrier to forecasting in fog and waiting for the fog to clear before being certain of what will happen next.
This barrier refers to periods when computer models for seasonal climate forecasts tend to have less reliable predictions than at other times of the year. Greater uncertainty means there is less confidence in this scenario, even though observational signs are beginning to point to El Niño progressing and computer models indicate it is likely to occur in the coming months.
Typically, El Niño forecasts tend to be more reliable in June as summer approaches.
