Chinese researchers have found that greenhouse warming and internal variability have increased the frequency of extreme El Nino and Central Pacific El Nino events since 1980.

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Edited by|HUGH GAY
CHINA SECTION- CJ JOURNALIST
14 FEB.2023- BEIJING
XINHUA

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      The research, conducted by a team of scientists at the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences, was recently published in the journal Nature Communications.

According to the researchers, El Nino has changed its properties since the 1980s, characterized by more common extreme El Nino and Central Pacific El Nino events. However, it had been unclear whether such change is externally forced or part of the natural variability.

The researchers investigated the past changes in El Nino diversity and quantified the contribution of anthropogenic forcing and internal variability to the recently observed El Nino diversity.

They found that the frequency of extreme El Nino and Central Pacific El Nino events also increased during the period 1875-1905 when the anthropogenic carbon dioxide concentration was relatively lower.

They determined that the frequent occurrence of extreme El Nino and Central Pacific El Nino events since 1980 was caused by the combination of anthropogenic forcing and internal variability associated with the Atlantic Multidecadal Oscillation (AMO).

Researchers revealed that a positive AMO enhances the zonal sea surface temperature gradient in the Central Pacific, strengthening zonal advective feedback and favoring extreme and Central Pacific El Nino development.

"Understanding the variation of observed El Nino may help more accurately project El Nino's future change," said Huang Gang, the corresponding author of the study and a researcher at IAP

Elnino is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (approximately between the International Date Line and 120°W), including the area off the Pacific coast of South America. The ENSO is the cycle of warm and cold sea surface temperature (SST) of the tropical central and eastern Pacific oceans. El Niño is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific. El Niño phases are known to last close to four years; however, records demonstrate that the cycles have lasted between two and seven years. During the development of El Niño, rainfall develops between September–November. clarification is needed The cool phase of ENSO is Spanish: La Niña lit. 'The Girl', with SSTs in the eastern Pacific below average, and air pressure high in the eastern Pacific and low in the western Pacific. The ENSO cycle, including both El Niño and La Niña, causes global changes in temperature and rainfall.

Developing countries that depend on their own agriculture and fishing, particularly those bordering the Pacific Ocean, are usually the most affected. In this phase of the Oscillation, the pool of warm water in the Pacific near South America is often at its warmest about Christmas. The original phrase, El Niño de Navidad, arose centuries ago when Peruvian fishermen named the weather phenomenon after the newborn Christ.