Environmental Engineering Reference
In-Depth Information
FIGURE O.2 Median runoff sensitivities (per degree of global warming) relative to 1971-2000 over 68 model
pairs. Each pair consisted of an average over A2, A1B, and B1 global emissions scenarios of one IPCC As-
sessment Report 4 (AR4) GCM model's output, derived from 30-year runoff averages centered on the years
for which the global average temperature increases were 1.0°C, 1.5°C, and 2.0°C, minus the 30-year model
average runoff for 1971-2000, divided by the global temperature change. This analysis was performed for
23 models for 1.0°C and 1.5°C increases, and 22 models for a 2.0°C increase. Results are shown as averages
over GCM grid cells (upper plot) or U.S. hydrological regions (lower plot). The notation a/b in each river basin
denotes the mean change in percent (a), and the agreement among models (b); expressed as the fraction
with positive changes minus the fraction with negative changes (FPN); see also Table 5.3. Table 5.3 contains
standard errors and consistency across models, as indicated by FPN.
