Joint Front Range Climate Change Study SOW

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Background Information Scientific understanding of the Earth's long -term and short -term climate trends has increased over the past several years. Included in this increased understanding are developments in modeling techniques used to project current changes and past trends, and to predict future possibilities at the global, regional, and local levels. Future global climate projections have been modeled using different emission scenarios determined by variables including economic growth, population growth, varying energy sources, and environmental sustainability. These modeled scenarios consistently predict that global average surface temperatures will rise. The most current quantitative results predict that the mean global surface temperature will increase by 0.8 to 4 °C by 2099 (these values are considered "Best estimates" and come from the IPCC AR4 report). Possible changes in North America's climate include greater annual warming across the continent as compared with global projections. A decrease in snow depth and season length is likely to occur corresponding to a warming climate trend. Across the southwest United States in particular, there may be a decrease in annual precipitation and an increase in average summer temperatures. Though this information comes from the latest scientific studies, it is important to note that the uncertainty in these projections is large and the stated results should be considered only as future possibilities. Scientific studies have shown that hydrologic systems and water resources are sensitive to climate change and variability, and that such changes add further stress to already over allocated water basins. The June 2006 Western Governor's Association Report stated the average temperatures in the West have risen 2 -5 °F during the 1900s and are predicted to continue rising. The possible local vulnerabilities (i.e. how susceptible a system is to sustaining damage from climate change) to Colorado's water basins due to the previously described global and continental changes, and statewide temperature increases include: ■ Changes in precipitation including: • frequency and intensity, • phase (rain vs. snow), • temporal distribution (seasonality), and • spatial distribution (location), ■ Increases in water use, ■ Decreases in snowpack, ■ Earlier snowpack melt -off, ■ Increases in evaporation , • Changes in soil moisture, • frequent and extended extreme conditions (droughts and floods), ■ Increases in the frequency and duration of wildfires, ■ Erosion and sedimentation changes, ■ Water quality changes, and ■ Recreational and environmental impacts. Such impacts are likely to change the historical timing and yield of water systems throughout Colorado. The Joint Front Range Climate Change Vulnerability Study will