Global distribution of Köppen-Geiger climate types during the Last Glacial Maximum, Mid-Holocene, and present

This research presents Köppen-Geiger (K-G) climate type maps of the Last Glacial Maximum (LGM) of 21,000 years ago (21 ka), the mid-Holocene (MH) of 6 ka, and the present (1976-2005). Data used to calculate and map the K-G climate type are-year monthly mean 2-m air temperature and precipitation from the National Center for Atmospheric Research (NCAR) Community Climate System Model version 4 (CCSM4)-Community Atmosphere Model version 4 (CAM4) as part of the Coupled Model Intercomparison Project Phase 5 (CMIP5). Results suggest that the model depicts similar modern climate distributions as in data-based research, excepting a larger distribution of tropical wet-dry and humid subtropical types, and a smaller distribution of hot arid and hot semi-arid types. The modeled modern K-G climate types cover similar percentages of Earth's terrestrial and marine surface as during the MH, with slight enlargement of the tropical wet-dry and decreased area of mesothermal monsoonal hot summer type in the modern period. At the LGM, the K-G Polar (E) climate was far more extensive than in modern times, with concurrent decreases in area of the Tropical (A) climates. Because Köppen-type classifications are intended to mimic the biome distributions, these results may be helpful in identifying biotic realms from the geologic past and the potential vegetative response to future climate changes.