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Causes of exceptional atmospheric circulation changes in the Southern Hemisphere
Author(s) -
Marshall Gareth J.,
Stott Peter A.,
Turner John,
Connolley William M.,
King John C.,
LachlanCope Thomas A.
Publication year - 2004
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2004gl019952
Subject(s) - gcm transcription factors , climatology , southern hemisphere , northern hemisphere , general circulation model , environmental science , ozone depletion , atmospheric sciences , atmospheric circulation , ozone layer , climate model , climate change , stratosphere , geology , oceanography
We demonstrate that recent observed trends in the annual and austral summer Southern Hemisphere Annular Mode (SAM) are unlikely to be due to internal climate variability, since they exceed any equivalent‐length trends in a millennial General Circulation Model (GCM) control run with constant forcings. In contrast we show that observed trends in the SAM are consistent with the combined effects of anthropogenic and natural forcings in GCM simulations. As these trends begin prior to stratospheric ozone depletion we challenge the assertion that this process is primarily responsible for changes in the SAM. Moreover, anthropogenic forcings have a larger effect on the austral summer SAM in combination with natural forcings than when acting in isolation.