Clouds, aerosols, and trace gases accounted for a 40% annual reduction of the
outgoing surface signal using the CRM. The difference in Sout (control – burn) at the
surface was -13.9 ± 3.0 W m-2 (fig. S8). The difference at the tropopause, which is
approximately equal to the radiative forcing from the surface albedo changes, was -8.4 W
S7
m-2. This value represents the mean from 2002-2004. Our error estimate for this forcing
reflects both interannual variability in Sout caused by variations in snow cover (± 1.8 W
m
-2) and a subjective assessment of uncertainty introduced from the use of the CRM (±
1.0 W m-2) for a total of ± 2.8 W m-2. For this period, 3-5 years after fire, summer albedo
was higher in the recent burn than in the control from the establishment of grasses, small
shrubs, and other changes in the surface. As a result, 24% of the annual radiative forcing
was a result of fire-induced albedo changes during summer (May-September).