FIGURE 4.15 September sea-ice extent as projected by the six models that simulated the mean minimum and seasonality with less than 20% error of the observations. The colored thin line represents each ensemble member from the same model under A1B (blue solid) and A2 (magenta dashed) emission scenarios, and the thick red line is based on HadISST analysis. Grey lines in each panel indicate the time series from the control runs (without anthropogenic forcing) of the same model in any given 150-year period. The horizontal black line shows the ice extent at 4.6 million km2 value, which is the minimum sea-ice extent reached in September 2007 according to HadISST analysis. All six models show rapid decline in the ice extent and reach ice-free summer (<1 million km2) before the end-of-the-21st-century. Source: Wang and Overland (2009): their Figure 1).