Indices of Sahel rainfall variability. Observations using the average of stations between 10°N and 20°N, 20°W and 40°E. Model values were based on the ensemble-mean average of grid-boxes between 10°N and 20°N, 20°W and 35°E. The correlation between observed and modeled indices of (July-September) rainfall over 1930–2000 is 0.60. (Time series are standardized to allow for an immediate comparison, because variability in the climate models is muted in comparison to observations. The ratio of observed to ensemble-mean standard deviations in the Sahel is 4.) This is Figure 1 in (Giannini et al. 2003).