Considering Uncertainty in Projections of Hydrological Extremes under Climate Change Scenarios in the Catskill Mountains Associated with Decadal-Scale Variability

Global Climate Models (GCMs) predict increasing temperature and precipitation trends in the Catskill Mountain region of south-central New York State, USA. However, these models underestimate the magnitude of decadal scale variability compared to observed precipitation in this region, resulting in their inability, when forced by historical boundary conditions, to capture certain features of historical variations such as the drought of record during the 1960s. In this study we examine the implications of this feature of GCM simulations for projections of future hydrological extremes, including drought as well as flooding with regards to both extreme precipitation events as well as antecedent conditions. Empirical historical analyses are combined with GCM results and hydrological modeling studies to consider whether and how GCM underestimation of decadal scale variations may be incorporated into uncertainty estimates of future scenarios for extreme hydrological events.