Sustainable Transportation Energy Pathways (STEPS)
Available online doi: 10.1007/s10584-015-1403-5
Morrison, Geoffrey M., Sonia Yeh, Anthony R. Eggert, Christopher Yang, James Nelson, Ana Mileva, Josiah Johnston, Daniel M. Kammen, Jeffery Greenblatt, Max Wei, Christina Zapata, Raphael Isaac, Mark Z. Jacobson, David Roland-Holst, Ray Williams, John Weyant (2015) Comparison of Low-Carbon Pathways for California. Climatic Change April 2015 (doi: 10.1007/s10584-015-1403-5)
Jurisdictions throughout the world are contemplating greenhouse gas (GHG) mitigation strategies that will enable meeting long-term GHG targets. Many jurisdictions are now focusing on the 2020–2050 timeframe. We conduct an inter-model comparison of nine California statewide energy models with GHG mitigation scenarios to 2050 to better understand common insights across models, ranges of intermediate GHG targets (i.e., for 2030), necessary technology deployment rates, and future modeling needs for the state. The models are diverse in their representation of the California economy: across scenarios with deep reductions in GHGs, annual statewide GHG emissions are 8–46% lower than 1990 levels by 2030 and 59–84% lower by 2050 (not including the Wind-Water-Solar model); the largest cumulative reductions occur in scenarios that favor early mitigation; non-hydroelectric renewables account for 30–58% of electricity generated for the state in 2030 and 30–89% by 2050 (not including the Wind-Water-Solar model) ; the transportation sector is decarbonized using a mix of energy efficiency gains and alternative-fueled vehicles; and bioenergy is directed almost exclusively towards the transportation sector, accounting for a maximum of 40% of transportation energy by 2050. Models suggest that without new policies, emissions from non-energy sectors and from high-global-warming-potential gases may alone exceed California’s 2050 GHG goal. Finally, future modeling efforts should focus on the: economic impacts and logistical feasibility of given scenarios, interactive effects between two or more climate policies, role of uncertainty in the state’s long-term energy planning, and identification of pathways that achieve the dual goals of criteria pollutant and GHG emission reduction.