A Review of the Major Studies to Reduce Emissions By 80%

Several studies conclude that deep reductions in anthropogenic carbon dioxide (CO₂) emissions from the global energy systems are required by mid-century to mitigate climate change. A review and inter-comparison was conducted of more than a dozen representative scenarios from the literature describing how CO₂ reductions in the range of 50-80 percent could be achieved by 2050. The studies varied significantly in their reliance on energy efficiency, electrification, renewable energy, nuclear power, fossil energy with carbon capture and storage (CCS) and sources of low-carbon transportation fuels.

Four conclusions emerge from this review. First, the pace of energy system transformation required to meet deep carbon reduction targets is substantially higher, and in some cases orders of magnitude higher, than historical experience. At a minimum, achieving this pace of transition will require significantly more “technology push” and “demand pull” efforts and policies. Second, given the scale of the challenge and the substantial social, technical, and economic hurdles faced by all available low-carbon energy technologies, removing any particular technology from consideration is likely to limit the chance of success. Third, given the constraints associated with scale up of low carbon technology at the pace described in the scenarios, substantial investments in research, development, demonstration, and deployment (RDD&D) are required to expand and improve our range of feasible decarbonization options. Finally, future studies of decarbonization pathways should explicitly describe their assumptions, relate them to historical experience, and describe key implementation hurdles and solutions; otherwise, such studies are little more than arithmetic exercises describing hypothetical futures.