Figure SPM-3: Projected
changes in average annual water runoff by 2050, relative to average runoff for
1961-1990, largely follow projected changes in precipitation. Changes in
runoff are calculated with a hydrologic model using as inputs climate projections
from two versions of the Hadley Centre atmosphere-ocean general circulation model
(AOGCM) for a scenario of 1% per annum increase in effective carbon dioxide concentration
in the atmosphere: (a) HadCM2 ensemble mean and (b) HadCM3. Projected increases
in runoff in high latitudes and southeast Asia, and decreases in central Asia,
the area around the Mediterranean, southern Africa, and Australia are broadly
consistent across the Hadley Centre experiments, and with the precipitation projections
of other AOGCM experiments. For other areas of the world, changes in precipitation
and runoff are scenario- and model-dependent.
