Policy Implications of Global Energy Scenarios for Climate Stabilization

Though greenhouse gas emission scenarios are widely cited in climate science studies and policy analysis, there is a persistent gap in communication and understanding between the scenario analysts whose models generate the emission paths and the scientists and policy analysts who use them. To more clearly identify the sources of emission reductions in stabilization scenarios, this study explores a method for a detailed decomposition that quantifies the following categories: demand reduction (including structural transformation in the economy, end-use energy efficiency, and improvements to energy supply efficiency), switching from fossil fuels to specific zero carbon energy sources, carbon sequestration, land use change, and reduction of non-CO2 gases. The study applies such a mitigation decomposition technique to scenario results generated by multiple models, drawing on a sample set that includes a variety of reference scenarios constrained to relatively low stabilization targets. The range of results reflects uncertainty about the numerous technology transition paths in the energy sector that could possibly achieve the stabilization targets. One policy-relevant finding is that energy efficiency appears to be a substantially underutilized source of mitigation in some of the global energy scenario models. This finding suggests that stabilization scenarios generated by those models could reach their target levels at a lower cost of mitigation than previously reported and could achieve even lower stabilization levels than attempted to date.