An unusually long La Niña has ended after three years, and the tropical Pacific is currently in an ENSO-neutral state (neither El Niño nor La Niña). According to the WMO update, which is based on input from the WMO Global Producing Centers of Long-Range Forecasts and an expert assessment, "there is a 60 percent probability of a transition from ENSO-neutral to El Niño in May-July 2023, increasing to about 70 percent in June-August and 80 percent between July and September. There is no indication of the strength or duration of El Niño at this time.
The WMO El Niño/La Niña Update was produced through extensive collaboration between the WMO, the WMO and the International Research Institute for Climate and Society (IRI) USA, and is based on contributions from experts around the world, including the Bureau of Meteorology (BoM), Centro Internacional para la Investigación del Fenómeno El Niño (CIIFEN), China Meteorological Administration (CMA), Climate Prediction Center (CPC) and Pacific ENSO Applications Climate (PEAC) Services of the National Oceanic and Atmospheric Administration (NOAA) USA, European Centre for Medium Range Weather Forecasts (ECMWF), Météo-France, India Meteorological Department (IMD), Indian Institute of Tropical Meteorology (IITM), International Monsoons Project Office (IMPO), Japan Meteorological Agency (JMA), Korea Meteorological Administration (KMA), Met Office of the United Kingdom, Meteorological Service Singapore (MSS), WMO Global Producing Centers of Long Range Forecasts (GPCs-LRF), including the Lead Center for Long Range Forecast Multi-Model Ensemble (LC-LRFMME).
WMO Secretary General Petteri Taalas points out that "We have just experienced the 8 warmest years on record, although we have had a cooling La Niña for the last 3 years, which has acted as a temporary brake on global temperature rise. The development of an El Niño will most likely lead to a new increase in global warming and increase the possibility of breaking temperature records." According to the WMO's State of the Global Climate report, 2016 was the hottest year on record due to the "double whammy" of a very strong El Niño event and warming from anthropogenic greenhouse gases.
The effect of El Niño on global temperatures is usually felt in the year following its development, so it is likely to be most noticeable in 2024, which is why Taalas warned that "the world should prepare for the development of El Niño, which is often associated with increased heat, drought or precipitation in different parts of the world. It could bring relief from drought in the Horn of Africa and other La Niña-related impacts, but it could also trigger more extreme weather and climate events. This underscores the need for the UN's Early Warnings for All initiative to keep people safe.
No two El Niño events are the same, and the impacts depend in part on the time of year. The WMO and national meteorological and hydrological services will therefore be closely monitoring developments. El Niño is a natural climate pattern associated with warming sea surface temperatures in the central and eastern tropical Pacific Ocean. It occurs on average every 2 to 7 years, and episodes typically last 9 to 12 months. El Niño events are typically associated with increased precipitation in parts of southern South America, the southern United States, the Horn of Africa, and central Asia. El Niño can also cause severe droughts in Australia, Indonesia, and parts of southern Asia. During the boreal summer, warm water from El Niño can fuel hurricanes in the east-central Pacific, while inhibiting hurricane formation in the Atlantic basin.
El Niño and La Niña are the main drivers of the Earth's climate system, but not the only ones: in addition to the ENSO update, the WMO regularly publishes Global Seasonal Climate Updates (GSCUs), which include the influences of other major climate drivers such as the North Atlantic Oscillation, the Arctic Oscillation, and the Indian Ocean Dipole. The latest update states, "As warmer than average sea surface temperatures are generally expected in oceanic regions, they contribute to a widespread forecast of above-normal temperatures over land areas. Without exception, positive temperature anomalies are forecast over all land areas in both the Northern and Southern Hemispheres".
Since February, there has been a significant increase in sea surface temperatures in the equatorial Pacific, with significantly more warming along the coast of South America. By mid-April, sea surface temperatures and other atmospheric and oceanic indicators in the east-central tropical Pacific are consistent with neutral ENSO conditions. In the atmosphere, convective activity over the equatorial Pacific near the given change line is almost normal. However, that the Northern Hemisphere's "'spring predictability barrier," a period characterized by slightly lower predictive capabilities, has not yet passed. Wmo concludes, "These recent developments in oceanic and atmospheric conditions in the tropical Pacific, together with current forecasts and expert assessments, indicate a strong likelihood of the onset of El Niño early in the second half of 2023 and its continuation during the remainder of the 6-month monthly forecast period."
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