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  • Cai, W, and T. Cowan, 2006: SAM and regional rainfall in IPCC AR4 models: Can anthropogenic forcing account for southwest Western Australian winter rainfall reduction?. Geophys. Res. Lett., 33, L24708, doi:10.1029/2006GL028037.

Winter rainfall over southwest Western Australia
(SWWA) has decreased by 20% since the late 1960s.
Why has the reduction occurred in the Southern Hemisphere
(SH) winter months but not in summer? To what extent is
this reduction attributable to anthropogenic forcing and
congruent with the Southern Annular Mode (SAM)?
Using reanalysis data and the Intergovernmental Panel on
Climate Change 4th Assessment Report (IPCC AR4)
20th century model experiments, we show that a SAM-SWWA
relationship exists in winter and not in other
seasons. An ensemble result from 71 experiments reveals
that anthropogenic forcing contributes to about 50% of the
observed rainfall decline. Approximately 70% of the
observed trend is congruent with the SAM trend, whereas
for the models it is 46%. Our result suggests that other
forcing factors must be invoked to fully account for the
observed rainfall reduction.

Full Article: http://www.agu.org/journals/gl/gl0624/2006GL028037/

Last Updated: 2007-12-12

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