Validating CCSM3 paleoclimate data using pollen-based reconstruction in the intermountain west

The use of spatially gridded paleoclimate data in niche modeling has become much more popular over the past decade. However, the datasets used are often derivative products produced from a coarse spatial resolution general circulation model, necessitating downscaling to make the data more meaningful to those studying organisms with restrictive geographic ranges. Knowing that researchers depend upon climate modelers to accurately recreate past climate regimes, this study compares the results from the downscaled and debiased Community Climate System Model 3 to pollen-based reconstructions for 27 sites in Wyoming, USA. Our comparison shows major disparities between the two climate reconstructions with average annual precipitation and actual evapotranspiration performing the best of six variables. This study demonstrates that models that evaluate climate envelopes for organisms whose habitat overlaps both montane regions and lower elevations, should carefully evaluate these types of downscaling efforts prior to making assumptions about an organism's climate niche space.