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112 assessment of climate change in the southwest united statesFigure 6.7 Annual precipitation change (in inches) from the historical simulation for thelow-emissions scenario (left), the high-emissions scenario (middle), and percentage ofhistorical simulation compared to the high-emissions scenario (right). Early- (2021–2050),mid- (2041–2070) and late- (2070–2099) twenty-first century periods shown in top, middle and bottompanels. Values shown are the median of sixteen simulations downscaled via BCSD. Source: BiasCorrected and Downscaled World Climate Research Programme's CMIP3 Climate Projections archiveat http://gdo-dcp.ucllnl.org/downscaled_cmip3_projections/#Projections:%20Complete%20Archives.the four GCMs used in the NARCCAP experiment are shown for 2055 (high-emissionsscenario only). All the mean changes are negative, although the values are rather smalloverall. For the high-emissions scenario, the CMIP3 models project average decreasesof around 2% in 2035, 4% by 2055, and about 5% by 2085. The decreases for the lowemissionsscenario are only slightly smaller; in 2085 the decrease is 2%, compared to 5%for high-emissions. The mean of the NARCCAP simulations is more negative than themean of the CMIP3 GCMs or the mean of the four GCMs used in the NARCCAP experiment,although the differences are small. The range of individual model changes is largecompared to the differences in the ensemble means, as also illustrated by the spread of