 The implications of 21st century climate change on the hydrology and water resources of the Colorado River Basin were assessed using a multi-model ensemble approach. Downscaled and bias corrected output from 11 general circulation models, GCMs, was used to drive macro-scale hydrology and water resources models. Ensembles of downscaled precipitation and temperature, and derived stream flows and reservoir system performance, were assessed through comparison with current climate simulations for the 1950 N-dash, 1999 historical period. For each of the 11 GCMs, two emission scenarios, IPCC-SREZ A2 and B1, were represented. Results for the A2 and B1 climate scenarios were divided into three periods, 2010 N-dash, 2039, 2040 N-dash, 2069, and 2070 N-dash, 2099. The mean temperature change averaged over the 11 ensembles for the Colorado Basin for the A2 emission scenario ranged from 1.2 to 4.4 N-dag, C for periods 1 N-dash, 3, and for the B1 scenario from 1.3 to 2.7 N-dag, C, precipitation changes were modest, with ensemble mean changes ranging. This article was authored by N. S. Christensen and D. P. Lettenmayer. We are article.tv, links in the description below.