Tropical eastern Pacific cooling trend reinforced by human activity

Abstract It remains unresolved whether the La Niña-like sea surface temperature (SST) trend pattern during the satellite era, featuring a distinct warming in the northwest/southwest Pacific but cooling in the tropical eastern Pacific, is driven by either external forcing or internal variability. Her...

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Published inNPJ climate and atmospheric science Vol. 7; no. 1; pp. 170 - 12
Main Authors Chung, Eui-Seok, Kim, Seong-Joong, Lee, Sang-Ki, Ha, Kyung-Ja, Yeh, Sang-Wook, Kim, Yong Sun, Jun, Sang-Yoon, Kim, Joo-Hong, Kim, Dongmin
Format Journal Article
LanguageEnglish
Published London Nature Publishing Group 24.07.2024
Nature Portfolio
Subjects
Aerosols
Climate change
Climate models
Cooling
El Nino
Global warming
Human influences
La Nina
Ozone
Ozone depletion
Pattern analysis
Sea surface temperature
Trade winds
Trends
Variability
Wind effects
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Summary:Abstract It remains unresolved whether the La Niña-like sea surface temperature (SST) trend pattern during the satellite era, featuring a distinct warming in the northwest/southwest Pacific but cooling in the tropical eastern Pacific, is driven by either external forcing or internal variability. Here, by conducting a comprehensive analysis of observations and a series of climate model simulations for the historical period, we show that a combination of internal variability and human activity may have shaped the observed La Niña-like SST trend pattern. As in observations, SSTs in each model ensemble member show a distinct multi-decadal swing between El Niño-like and La Niña-like trend patterns due to internal variability. The ensemble-mean trends for some models are, however, found to exhibit an enhanced zonal SST gradient along the equatorial Pacific over periods such as 1979–2010, suggesting a role of external forcing. In line with this hypothesis, single-forcing large ensemble model simulations show that human-induced stratospheric ozone depletion and/or aerosol changes have acted to enhance the zonal SST gradient via strengthening of Pacific trade winds, although the effect is model dependent. Our finding suggests that the La Niña-like SST trend is unlikely to persist under sustained global warming because both the ozone and aerosol impacts will eventually weaken.
ISSN:2397-3722
2397-3722
DOI:10.1038/s41612-024-00713-2