Analysis of Historical and CMIP5 Projections of Multi-decadal Climatic Variation and Implications for Ecosystem Management on the Colorado Plateau

Abstract:

Increasing pressures on ecosystems of the Colorado Plateau, in particular changes in land use and anthropogenically forced changes in climate, are moving these systems toward “thresholds” that may not be re-traversed once crossed. Recent studies have shown that changes in winter temperature and hydrological fluxes in the western United States are outside the range of natural variability. These observations suggest that the Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO) are acting synergistically with underlying climatic trends associated with increased greenhouse gas forcings. Of particular importance for the Colorado Plateau (CP), future warming may alter the position and strength of the North American Monsoon (NAM), which is responsible for a sharp summertime moisture gradient across the region. Natural resource managers are faced with unprecedented challenges if these trends continue. The goal of the project was to describe historical and future projected inter-annual and multi-decadal variability of precipitation in the northern limits of the NAM region, analyze future projected changes on the hydrological regime, and discuss implications for management of these semi-arid ecosystems. Daily climate records were analyzed to quantify the current and historical spatio-temporal pattern of precipitation across the CP using results from ten CMIP5 climate models that best reproduce climate metrics of PDO and ENSO across the study area. Results suggest that a focus on the variability and pattern change in extreme climate anomalies, is vital to inform the management of natural resources. Specifically, inter- and intra-annual variability, seasonality of temperature and precipitation, as well as interactions between multi-decadal cycles trends driven by large-scale climate dynamics, need to be considered. Policies that guide management actions into the future should be based on strategies that cover a wide range of plausible climatic conditions.