Assessment of possible changes in the El Niño and La Niña repeatability by the end of the XXI century using the CMIP6 models

by

E.N. Voskresenskaya1, O.V. Marchukova1, V.V. Afanasyeva2

 Institute of Natural and Technical Systems, RF, Sevastopol, Lenin St., 28

Lomonosov Moscow State University Branch in Sevastopol,

RF, Sevastopol, Geroyev Sevastopolya St., 7

E-mail: elena_voskr@mail.ru

DOI: 10.33075/2220-5861-2021-4-14-21

UDC 551.583 

Abstract:

   The quality of SST anomalies revealed in the equatorial Pacific associated with El Niño and La Niña in the CMIP6 project models (KIOST-ESM, MIROC-ES2L and INM-CM4-8) was evaluated by comparing with real events in the period 1950 to 2014 using the ERSSTv5 data sets. It is shown that the ensemble model estimation of the number, intensity and duration of EN and LN corresponds quite well to real conditions. On this basis, the corresponding model ensemble calculations of their future possible changes in 2021–2085 relative to the historical 1950–2014 period were carried out for two possible scenarios: business-as-usual (SSP2-4.5) and negative (SSP5-8.5).

   The frequency of El Niño events will decrease by 30% under the SSP2-4.5 scenario. However, taking into account the fact that the ensemble of models underestimated their number by exactly this value when compared with real data, it should be assumed that the frequency of El Nino occurrences will not change. Moreover, their average intensity and duration will also remain. At the same time, the number of La Niña will increase by 26.6%, their average intensity will decrease by only 3%, and the duration of events will remain unchanged.

   According to the extreme scenario SSP5-8.5, the El Nino formation will decrease by 40%. In the interpretation of the result, in comparison with the actually observed El Nino events, their number will decrease by 10%, their average intensity will decrease by 13%, and the duration will increase by 20%. The number of La Nina will double in the next 65 years, but their intensity and duration will slightly decrease by 2–4%.

Keywords: El Niño, La Niña, CMIP6, ocean surface temperature, long-term forecast.

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