THE DUST BOWL OF THE 1930S - ANALOG OF GREENHOUSE-EFFECT IN THE GREAT-PLAINS

For nine sites in the southern Great Plains, the decade of the Dust Bowl was consistently warmer than 1951 to 1980 ''normal.'' It also tended to be drier, but less consistently so. At four of the nine sites, the combination of consistently higher temperature and mostly lower precipitation had a cumulative effect over the 1930s, making the entire decade a period of agricultural drought as characterized by the Palmer Drought Severity Index (PDSI). Episodes of extreme drought occurred at many sites, particularly in 1934 in Nebraska. Temperature and precipitation changes predicted by two general circulation models (GCMs) at the upper range of current climate model predictions for doubled concentrations of CO2 + 4.2-degrees-C and + 4.0-degrees-C mean global surface air temperature warming) suggest drought conditions as defined by the PDSI that are worse than those for the 1930s for all stations. Droughtiness is projected to increase overall, even when the GCM climate change scenarios produce little change or even increases in precipitation. In most instances, the mean GCM-predicted drought conditions equal or exceed the extreme drought years of the decade. When dynamic crop growth models were run in combination with the GCM-predicted climates, simulated wheat (Triticum aestivum L.) and corn (Zea mays L.) yields were obtained that were generally lower (approximately 30%) than those of simulations for the actual climate of the 1930s. The crop model simulations indicated that the predicted climate change is likely to be less detrimental to a crop such as wheat, whose main growing period is in the spring, than to a typical summer crop such as corn. The overall results of this study suggest that the Dust Bowl experience of the 1930s may be characterized as a preliminary analog of possible future climate conditions for the southern Great Plains, with the importance difference that the higher projections of GCM warming produce more severe climatic consequences than the Dust Bowl.