This study explores the effects of atmospheric CO 2 enrichment and climate change on soil moisture (W r ) and biome-level water limitation (L TA ), using a dynamic global vegetation and water balance model forced by five different scenarios of change in temperature, precipitation, radiation, and atmospheric CO 2 concentration, all based on the same IS92a emission scenario. L TA is defined as an index that quantifies the degree to which transpiration and photosynthesis are co-limited by soil water shortage (high values indicate low water limitation). Soil moisture decreases in many regions by 2071-2100 compared to 1961-1990, though the regional pattern of change differs substantially among the scenarios due primarily to differences in GCM-specific precipitation changes. In terms of L TA , ecosystems in northern temperate latitudes are at greatest risk of increasing water limitation, while in most other latitudes L TA tends to increase (but again varies the regional pattern of change among the scenarios). The frequently opposite direction of change in W r and L TA suggests that decreases in W r are not necessarily felt by actual vegetation, which is attributable mainly to the physiological vegetation response to elevated CO 2 . Without this beneficial effect, the sign of change in L TA would be reversed from predominantly positive to predominantly negative.