The scientific evidence is clear that the Earth's climate is warming (IPCC AR4 2007). Multiple independent measurements confirm widespread warming in the Western U.S.; in Colorado, temperatures have increased by approximately 2°F from 1977–2006. Increasing temperatures are affecting the state's water resources.

In response to the risks associated with global warming, Governor Ritter issued the Colorado Climate Action Plan (CCAP) in 2007. The CCAP sets out a goal to prepare the state to adapt to those climate changes “that cannot be avoided.” Recommendations in the CCAP include assessing the vulnerability of Colorado's water resources to climate change, analyzing impacts on interstate water compacts, and planning for extreme events such as drought and flooding (CCAP 2007).

Here, we present the synthesis findings from the report: Climate Change in Colorado: A Synthesis to Support Water Resources Management and Adaptation. The objective of the document is to communicate the state of the science regarding the physical aspects of climate change that are important for evaluating impacts on Colorado's water resources. Accordingly, the document focuses on observed trends, modeling, and projections of hydroclimatic variables that are important for Colorado's water supply. Projections are reported out to 2050, as this is the relevant time frame for development of adaptation strategies.

Although many published datasets include information about Colorado, there are few climate studies that focus only on the state. Consequently, many important analyses for Colorado are lacking. The Climate Change in Colorado Report summarizes Colorado-specific findings from peer-reviewed regional studies, and presents new graphics derived from existing datasets. The state is home to many experts in climate and hydrology, and this report also draws from ongoing work by these scientists.

The strategy for framing this document in terms of Colorado's water-related adaptation needs, and the challenges of communicating the necessary information to a diverse audience, will also be presented.