Spectral shifts in log (ν)−log (S) for Regions 3, 6, 9, and 10 in panel a). The dashed red line shows the best linear fit to the data points. Shifted data points giving the global spectrum are given in panel b). Different colours are used to indicate the data points belonging to different regions. The best JP and KGJP model fits are plotted with dashed-dot red and green lines, respectively (overlapping, since there is essentially no difference between the models for these regions).