Achieving California's 80% greenhouse gas reduction target in 2050: Technology, policy and scenario analysis using CA-TIMES energy eco- nomic systems model Christopher Yang a,n , Sonia Yeh a , Saleh Zakerinia a , Kalai Ramea a , David McCollum b a Institute of Transportation Studies, University of California, 1715 Tilia Street, Davis, CA 95616, USA b International Institute for Applied Systems Analysis, Laxenburg 2361, Austria HIGHLIGHTS  We model the California Energy System to 2050 under policy and technology scenarios.  The model optimizes technology and resource investments to meet emissions targets.  Deep emissions cuts ( 474%) are achieved across all reduction scenarios.  Carbon capture enables negative emission biofuels and allows more petroleum use.  Greenhouse gas mitigation cost is small compared with total economic activity. article info Article history: Received 11 June 2014 Received in revised form 18 November 2014 Accepted 4 December 2014 Keywords: Carbon emissions Optimization Electricity Transportation Fuels Energy services abstract The CA-TIMES optimization model of the California Energy System (v1.5) is used to understand how California can meet the 2050 targets for greenhouse gas (GHG) emissions (80% below 1990 levels). This model represents energy supply and demand sectors in California and simulates the technology and resource requirements needed to meet projected energy service demands. The model includes as- sumptions on policy constraints, as well as technology and resource costs and availability. Multiple scenarios are developed to analyze the changes and investments in low-carbon electricity generation, alternative fuels and advanced vehicles in transportation, resource utilization, and efficiency improve- ments across many sectors. Results show that major energy transformations are needed but that achieving the 80% reduction goal for California is possible at reasonable average carbon reduction cost ($9 to $124/tonne CO 2 e at 4% discount rate) relative to a baseline scenario. Availability of low-carbon resources such as nuclear power, carbon capture and sequestration (CCS), biofuels, wind and solar generation, and demand reduction all serve to lower the mitigation costs, but CCS is a key technology for achieving the lowest mitigation costs. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction California is one of the leading nations/states around the world in developing policy instruments to address the issue of climate change. In 2005, it set an aspirational long-term goal of reducing greenhouse gas (GHG) emission 80% below 1990 levels by 2050. The state subsequently implemented legislation setting a binding target that GHG emissions be brought back down to the 1990 level by 2020. This path to achieving the near-term GHG goal included implementation of a number of policy mechanisms including the cap-and-trade program, vehicle efficiency and fuel carbon stan- dards, and others (CARB, 2008). There is significant uncertainty as to how to achieve the deep reductions in GHG emissions that are needed to stabilize atmospheric concentrations of GHGs, what they would cost and what policy measures would be needed. The CA-TIMES model was developed to help answer some of these questions about how to achieve the long-term GHG emissions goals by 2050 while still meeting the demand for energy (McCollum et al., 2012). Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/enpol Energy Policy http://dx.doi.org/10.1016/j.enpol.2014.12.006 0301-4215/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. E-mail addresses: ccyang@ucdavis.edu (C. Yang), slyeh@ucdavis.edu (S. Yeh), mzakerinia@ucdavis.edu (S. Zakerinia), kramea@ucdavis.edu (K. Ramea), mccollum@iiasa.ac.at (D. McCollum). Energy Policy 77 (2015) 118–130