Relationship of anthropogenic change defined from a CMIP3 and, b CCSM4 with annual proportions of Cat 1–2 and Cat 4–5 hurricanes. Note the different scales for the ACCI. A 5-year running mean smoother has been used (indicated by the SM in the legend), thin solid (dashed) lines indicate linear (quadratic) trends, and all variances have p  0.01 (using unsmoothed data)