Imtiaz Rangwala, Ph.D.
Research Associate
Western Water Assessment/CIRES
CU - Boulder
http://wwa.colorado.edu/about/rangwala

Reconciling Global Climate Projections at Regional Scales in the 
Southwest US

Abstract
	There are substantial uncertainties in the extent and nature 
of climate change projections at regional scales from our 
global climate models (GCMs) that feed into the IPCC 
reports. The magnitudes of these uncertainties have not 
reduced with successive generations of GCMs, and they are 
expected to remain in the near future, in part, because of 
the existing design of the global modeling effort. These 
regional climate change uncertainties – which include, for 
example, large range in future simulated warming of several 
degrees, or increases or decreases in future precipitation – 
create a challenge for user community to reconcile this 
information and develop adaptation strategies for future 
climate change. In this presentation, I will explore the 
nature and causes of climate change uncertainties for the 
Southwest US, as well as some of the thinking and efforts to 
reconcile this information for user community to be 
actionable. I will also cover some examples related to 
downscaling of large-scale climate projections for use in 
impacts modeling, which produce additional layers of 
uncertainties, to explore the issue of decision-relevant 
climate downscaling.