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Updated 12 October, 2003
National Assessment of
are providing figures of time series of various indices from CGCM1 and
HADCM2 for you to get an idea of future trends in these indices.
Tony Barnston and Luke He (NOAA) have calculated the North Atlantic
Oscillation (NAO), Pacific North America (PNA), Pacific Decadal
Oscillation (PDO), and Southern Oscillation Index (SOI) for both
models. John Fyfe (CCCma) has calculated and published the
Arctic Oscillation for the CGCM1 model, which he has shown is more
sensitive to global warming than the NAO.
Figure 1: CGCM1 (DJF) SOI, PNA, and
NAO. The decrease in SOI is consistent with increasing El Nino-like
conditions (i.e. ENSO cycles continue but from a warmer base state that
roughly resembles current-day El Ninos). The increase in the PNA is
consistent with an increase in the strength of the Aleutian Low and the
trend in the PDO (Figure 3 below). While the NAO shows no trend, the
AO (Figure 4 below) does show an increasing trend into the future,
consistent with the historical trend.
Figure 2: HADCM2 (DJF) a) SOI,
PNA, and NAO b) Modified SOI (called SOI* on the plot), with
Tahiti's location shifted 12.5o northwards and closer to the
equator. The modified SOI index does show a slight decrease over
time, while the other indices do not show any strong trends.
Figure 3: Pacific Decadal Oscillation (PDO) for CGCM1 and HADCM2. Both models project an increase in the PDO, which is consistent with a strengthened Aleutian Low.
Figure 4: Arctic and Antarctic Oscillation (AO and AAO) time series from CGCM1 ensembles (November-April averages). Black curve: observed; blue curve: control simulation; red curves: transient simulations (the upper panel is the ensemble used in the National Assessment). [Fyfe, J.C. and Flato, G.M. 1999. 'The Arctic and Antarctic Oscillations and their projected changes under global warming. Geophysical Research Letters. 26(11):1601-1604.