Global warming and the weakening of the tropical circulation

Gabriel A. Vecchi, Brian J Soden

Research output: Contribution to journalArticle

726 Citations (Scopus)

Abstract

This study examines the response of the tropical atmospheric and oceanic circulation to increasing greenhouse gases using a coordinated set of twenty-first-century climate model experiments performed for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). The strength of the atmospheric overturning circulation decreases as the climate warms in all IPCC AR4 models, in a manner consistent with the thermodynamic scaling arguments of Held and Soden. The weakening occurs preferentially in the zonally asymmetric (i.e., Walker) rather than zonal-mean (i.e., Hadley) component of the tropical circulation and is shown to induce substantial changes to the thermal structure and circulation of the tropical oceans. Evidence suggests that the overall circulation weakens by decreasing the frequency of strong updrafts and increasing the frequency of weak updrafts, although the robustness of this behavior across all models cannot be confirmed because of the lack of data. As the climate warms, changes in both the atmospheric and ocean circulation over the tropical Pacific Ocean resemble "El Niño-like" conditions; however, the mechanisms are shown to be distinct from those of El Niño and are reproduced in both mixed layer and full ocean dynamics coupled climate models. The character of the Indian Ocean response to global warming resembles that of Indian Ocean dipole mode events. The consensus of model results presented here is also consistent with recently detected changes in sea level pressure since the mid-nineteenth century.

Original languageEnglish (US)
Pages (from-to)4316-4340
Number of pages25
JournalJournal of Climate
Volume20
Issue number17
DOIs
StatePublished - Sep 1 2007

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atmospheric circulation
global warming
Intergovernmental Panel on Climate Change
updraft
climate modeling
ocean
oceanic circulation
twenty first century
climate
thermal structure
sea level pressure
nineteenth century
mixed layer
greenhouse gas
thermodynamics
experiment
ocean circulation
Indian Ocean
Indian Ocean Dipole

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Global warming and the weakening of the tropical circulation. / Vecchi, Gabriel A.; Soden, Brian J.

In: Journal of Climate, Vol. 20, No. 17, 01.09.2007, p. 4316-4340.

Research output: Contribution to journalArticle

Vecchi, Gabriel A. ; Soden, Brian J. / Global warming and the weakening of the tropical circulation. In: Journal of Climate. 2007 ; Vol. 20, No. 17. pp. 4316-4340.
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