Climate Change, Land Use, and Environmental Sensitivity (CLUES2)

This project seeks to provide long-term perspectives on natural variability and on environmental impacts of past climatic changes on arid and semiarid Federal lands in the western United States (with a particular emphasis on the Holocene of the Upper Colorado River Basin). Our research addresses the nature, timing, and environmental effects of Late Quaternary climatic changes across this physiologically complex region, which encompasses geographic and elevational gradients in temperature, moisture, and the seasonality of precipitation. Consequently, we aim to reconstruct climatic and environmental variability and change for the past 25,000 years in four dimensions (time, latitude, longitude, and elevation) across a broad spatial coverage that captures the primary climatic gradients of this region.

The scientific work of the CLUES2 project includes characterizing the modern relations between climatic parameters and plant distributions; studying past changes in plant distributions, lake environments, and other environmental indicators; developing methods to obtain quantitative estimates of past climatic conditions (with associated uncertainty values); and, comparing our reconstructions with numerical model simulations of past climatic and environmental conditions.

Why is this research important?

Studies of the past reveal how much and how quickly climate can change, even without the potential effects of human actions. In the western United States, past climatic changes were complex, differed in degree across elevation, and included changes in mean conditions, variability, and seasonality. Ecosystem responses were also complex, with different species having different thresholds that caused either die offs in the previously acceptable ranges and/or opportunities for dispersal to new habitats. As a consequence, biotic communities were ephemeral and undergoing constant change. It should be expected that future climatic changes will also be complex, as will the environmental responses to these changes.

The comparison of paleoclimatic and paleoenvironmental reconstructions with model simulations for key past time periods provides information and insights that may be important in considering potential future changes. This comparison provides a basis for evaluating how well models can simulate conditions different from those of today. In addition, model simulations may indicate the climatic circulation patterns responsible for geographic and elevational patterns observed in the paleo reconstructions.

Principal Investigator: Robert S. Thompson

Project Team: Anderson, Katherine H.; Carrara, Paul E.; Dean, Walter E.; Honke, Jeffrey; Pelltier, Richard T.; Rosenbaum, Joseph G.; Skipp, Gary L.; Strickland, Laura E.; Thompson, Robert S.