Reconciling opposing Walker circulation trends in observations and model projections

Eui Seok Chung, Axel Timmermann, Brian J. Soden, Kyung Ja Ha, Lei Shi, Viju O. John

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

A strengthening of the Pacific Walker circulation (PWC) over recent decades triggered an intense debate on the validity of model-projected weakening of the PWC in response to anthropogenic warming. However, limitations of in situ observations and reanalysis datasets have hindered an unambiguous attribution of PWC changes to either natural or anthropogenic causes. Here, by conducting a comprehensive analysis based on multiple independent observational records, including satellite observations along with a large ensemble of model simulations, we objectively determine the relative contributions of internal variability and anthropogenic warming to the emergence of long-term PWC trends. Our analysis shows that the satellite-observed changes differ considerably from the model ensemble-mean changes, but they also indicate substantially weaker strengthening than implied by the reanalyses. Furthermore, some ensemble members are found to reproduce the observed changes in the tropical Pacific. These findings clearly reveal a dominant role of internal variability on the recent strengthening of the PWC.

Original languageEnglish (US)
Pages (from-to)405-412
Number of pages8
JournalNature Climate Change
Volume9
Issue number5
DOIs
StatePublished - May 1 2019

ASJC Scopus subject areas

  • Environmental Science (miscellaneous)
  • Social Sciences (miscellaneous)

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