Figure 8.16. Scatter plot of simulated springtime Δα_s/ΔT_s values in climate change (ordinate) vs simulated springtime Δα_s/ΔT_s values in the seasonal cycle (abscissa) in transient climate change experiments with 17 AOGCMs used in this report (Δα_s and T_s are surface albedo and surface air temperature, respectively). The climate change Δα_s/ΔT_s values are the reduction in springtime surface albedo averaged over Northern Hemisphere continents between the 20th and 22nd centuries divided by the increase in surface air temperature in the region over the same time period. Seasonal cycle Δα_s/ΔT_s values are the difference between 20th-century mean April and May α_s averaged over Northern Hemisphere continents divided by the difference between April and May T_s averaged over the same area and time period. A least-squares fit regression line for the simulations (solid line) and the observed seasonal cycle Δα_s/ΔT_s value based on ISCCP and ERA40 reanalysis (dashed vertical line) are also shown. The grey bar gives an estimate of statistical error, according to a standard formula for error in the estimate of the mean of a time series (in this case the observed time series of Δα_s/ΔT_s) given the time series’ length and variance. If this statistical error only is taken into account, the probability that the actual observed value lies outside the grey bar is 5%. Each number corresponds to a particular AOGCM (see Table 8.1 ). Adapted from Hall and Qu (2006).