These data were compiled for the study: Divergent climate change effects on widespread dryland plant communities driven by climatic and ecohydrological gradients. The objectives of our study were to (1) describe how climate change will alter the biomass and composition of key plant functional types; (2) quantify the impacts of climate change on future functional type biomass and composition along climatic gradients; (3) identify if and which geographic locations will be relatively unaffected by climate change while others experience large effects; and (4) determine if there is consistency in climate change impacts on plant communities among a representative set of climate scenarios. These data represent geographic patterns in simulated plant functional biomass of big sagebrush plant communities (cheatgrass, perennial forbs, C3 perennial grasses, C4 perennial grasses, perennial grasses, big sagebrush) as across-year averages of differences ("change") between projected future climates (years 2030-2060 and 2070-2100) derived from STEPWAT2 simulations run with each of 13 Global Climate Models (GCMs; CanESM2, CESM1-CAM5, CSIRO-Mk3-6-0, FGOALS-g2, FGOALS-s2, GISS-E2-R, HadGEM2-CC, HadGEM2-ES, inmcm4, IPSL-CM5A-MR, MIROC5, MIROC-ESM, and MRI-CGCM3; Maurer et al. 2007) that participated in CMIP5 for representative concentration pathways RCP4.5 and RCP8.5 and historical (years 1980-2010) values. Data of across-year averages of simulations under historical ("current"; years 1980-2010) climate and median differences ("change") between projected future climates (years 2030-2060 and 2070-2100) derived as medians across 13 Global Climate Models are available from the data release by Renne et al. (2021). These data were created in 2020 and 2021 for the area of the sagebrush region in the western U.S.A. These data were created by a collaborative research project between the U.S. Geological Survey, Marshall University, U.S. Fish and Wildlife Service, Yale University, and University of Wyoming, using a new multivariate matching algorithm (Renne et al., 202X.) which transfers simulated plant functional biomass of big sagebrush plant communities from 200 sites to a gridded product with 30-arcsecond spatial resolution. These data can be used with high resolution matching of projected decreases of big sagebrush, perennial C3 grass and perennial forb biomass in warm, dry sites; no projected change or increases in functional type biomass in cold, moist sites; and widespread projected increases in perennial C4 grasses across big sagebrush plant communities in the sagebrush region of the western U.S.A. (Palmquist et al. 2021) and within a scope as defined by the study. These data may also be used to evaluate the potential impact of changing climate conditions on geographic patterns in simulated plant functional biomass of big sagebrush plant communities within the scope defined by the study. In particular, these results will be useful for informing the design of long-term landscape conservation efforts to maintain and expand wildlife habitat across the sagebrush biome.