The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties
FIGURE 2-6 July-August average net daytime (12Z-23Z) radiation received at the surface for the pre-1900 landscape (top), 1989 large-scale meteorology with the 1993 landscape (middle), and the difference between the 1989 simulation and the pre-1900 case (bottom) in units of W m−2. The daytime land average for the pre-1900 case is 530 W m−2 and for the 1989 simulation is 503 W m−2. SOURCE: Adapted from Marshall et al. (2004b).
spacecraft have measured the total solar irradiance since the late 1970s. There is an 11-year cycle in total solar irradiance of peak-to-peak amplitude ~1 W m−2 (0.1 percent) in the past three cycles. Allowing for reflection of 30 percent of this incident energy (Earth’s albedo) and averaging over the globe, the corresponding climate forcing is of order 0.2 W m−2.
Multiple TSI datasets have been combined into a composite time series of daily total solar irradiance from 1979 to the present. This requires the cross-calibration of measurements made by overlapping datasets to adjust