Climate and Energy Action Plan (CEAP)

CLIMATE TRENDS & PRO JECTIONS | CITY OF ASHLAND, OREGON | FINAL REPORT | 6 Data & Method s This section summarizes data sources and methods of analysis used in this project. A detailed description of the data and methods is included at the end of the document. Historic al Trends The Oregon Climate Change Research Institute analyzed o bserved trends in annual and seasonal temperature and precipit ation from 1893 to 2014 using Ashland data fr om version 2.5 of the United States Historical Climate Networ k (Menne, Williams, & V ose, 2009) . The team analyzed o bserved trends in April 1 snow water equivalent (SWE) from 1960 to 2014 using SNOTEL and Snow Course data in the Rogue Basin collected by the Natural Resou rces Conservation Service . Trends were estimated using standard least squares linear regression . Future Projections The future climate projections for Ashland are based on the latest generation of global climate models (GCMs) from the Coupled Model Intercomparison Project phase 5 (CMIP5) (Taylor, Stouffer, & Meehl, 2012) that were used in the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC, 2013) . CMIP5 simulatio ns of the 21st century were driven by repres entative concentration pathways (RCPs) that define concentrations of greenhouse gases, aerosols, and chemically active gases leading to a set amount of radiative forcing —or extra energy trapped in the earth -atmos phere system —by the year 2100 (van Vuuren et al., 2011) . This project considers two of the four RCPs : RCP4.5 (“low”) representing moderate efforts to mitigate emissions , and RCP8.5 (“high”) representing a business as usual scenario (see Figure 1). It is imp ortant to note that RCP2.6, which attains negative greenhouse gas emissions by 2100, is the only RCP scenario to keep global temperature likely below 2°C (IPCC, 2013 ). Inherent in GCM projections is uncertainty due to emissions scenario, internal variabili ty, and modeling physics and resolution, which combined yield a range of plausible future climate projections rather than a single precise prediction. Figure 1. Carbon emissions and atmospheric carbon dioxide concentrations for RCP scenarios (Walsh et al., 2014a) . In a project cal led “Integrated Scenarios of the Future Northwest Environment,” the coarse resolution (100 - 300 km) of the CMIP5 GCM output was statistically downscaled to a resolution of about 6 km, which was then used as an input to hydrology and vegetation models. Model ed historical and future climate data was analyzed for the 6 -km grid cell containing the city of Ashland from 1950 to 2099 for 18 CMIP5 GCMs as well as RCP4.5 and RCP8.5. Historical and future April 1 SWE and total runoff data from the hydrology model were averaged over the Middle Rogue basin .