We used the Köppen-Geiger biome-climate classification scheme to produce a software tool for predicting global maps of vegetation boundary conditions (VBCs) (soil and plant type cover fractions, canopy heights, annual maximum and monthly leaf area index) for Earth System Model (ESM) simulations of vegetation-atmosphere coupling in alternative climates. A modern Köppen-Geiger biome map derived from observed mean monthly climatology (2001–2010) was used as a mask to characterize statistics of contemporaneous satellite-observed VBCs categorized into the 12 plant functional types (PFTs) of the Ent Terrestrial Biosphere Model. A lookup table (LUT) of these VBCs was then constructed tabulating VBCs for each Köppen-Geiger class. For paleo-vegetation back to the Cretaceous, additional algorithms were designed to replace grasses and deciduous trees with time-relevant cover types. To evaluate the efficacy of the lookup table and paleo-vegetation algorithms, we conducted both modern and Cretaceous climate simulations with the NASA Goddard Institute for Space Studies ESM ModelE-2.1 and its generalized planetary version. Climate simulations for the modern, 2001–2010, using the LUT-generated VBCs showed simulated climate to have no significant difference from using the original satellite-derived VBCs. For the Cretaceous Thermal Maximum, given a preliminary simulated climate having bare soil for the land surfaces, predicted maps of cover types largely capture the vegetation type patterns compared to fossil reconstructions, while reflecting a high latitude cold bias of the simulated climate. The "Ent Köppen-Geiger" v1.0 software tool is made available for community updates and studies with asynchronous vegetation-climate model coupling for past to future climates.