The San Diego Regional Decarbonization Framework’s Technical Report provides technical and policy pathways to decarbonization in the medium-term to inform near-term policymaking in regional, County, and city governments. The report models science-based pathways to net zero carbon emissions for the San Diego region by 2045, consistent with the Paris Climate Agreement and California State mandates. The pathways provide a shared vision for the San Diego region to collectively reduce net GHG emissions in alignment with California’s net zero goal. This report is a technical analysis of how different sectors in the energy system can contribute to decarbonization, but does not identify the “right” pathway. Instead, it shows numerous ways to achieve regional emissions goals in multiple sectors to highlight trade-offs, co-benefits, decision points, risks, and synergies. The analyses and pathways should be updated as technologies evolve or uncertainties are resolved or clarified. To that end, the report explores policy processes to help regional jurisdictions learn about uncertainties and adjust strategies as information arises.

Abstract A growing number of jurisdictions are passing ambitious clean energy policies. Yet few studies have accounted for natural and agricultural land impacts of low-carbon pathways and how environmental siting constraints affect electricity costs and technology choices. To address this gap, we developed an integrated land-energy planning framework to examine the land use trade-offs of renewable energy development required to achieve ambitious clean energy goals, using the state of California as a case study. Using high-resolution ecological and agricultural datasets for 11 Western U.S. states, we modeled environmentally-constrained onshore wind, solar photovoltaic, and geothermal potential and used an electricity capacity expansion model to build generation portfolios for 2050. Here we show that California can meet its targets, but the technology mix, spatial build-out, and system costs are sensitive to land protections and availability of out-of-state renewable resources. Results suggest that failure to consider land availability in energy planning could increase uncertainties, environmental impacts, and risks in meeting subnational climate targets.