Jim Williams

The Technology Path to Deep Greenhouse Gas Emissions Cuts by 2050: The Pivotal Role of Electricity

Electrifying Prospects Greenhouse gas emissions need to be reduced in order to decrease the risk of dangerous climate change, and a commonly advocated intermediate step to decarbonizing our energy production is to cut emissions by 80% by the year 2050. Williams et al. (p. 53, published online 24 November) analyze the infrastructure and technology requirements required to meet this goal in California and conclude that simply using the most technologically advanced types of energy supply now available will not be enough. Instead, transportation and other sectors will need to be converted largely to electrical systems, which would make decarbonized electricity the dominant form of energy supply. Such a transformation will require technologies that are not yet commercialized and intensive public-private and interindustry coordination at every stage of the process. Reducing greenhouse gas emissions to 80% below 1990 levels by 2050 requires widespread electrification of transportation and other sectors. Several states and countries have adopted targets for deep reductions in greenhouse gas emissions by 2050, but there has been little physically realistic modeling of the energy and economic transformations required. We analyzed the infrastructure and technology path required to meet California’s goal of an 80% reduction below 1990 levels, using detailed modeling of infrastructure stocks, resource constraints, and electricity system operability. We found that technically feasible levels of energy efficiency and decarbonized energy supply alone are not sufficient; widespread electrification of transportation and other sectors is required. Decarbonized electricity would become the dominant form of energy supply, posing challenges and opportunities for economic growth and climate policy. This transformation demands technologies that are not yet commercialized, as well as coordination of investment, technology development, and infrastructure deployment.

The need for national deep decarbonization pathways for effective climate policy

Constraining global average temperatures to 2 °C above pre-industrial levels will probably require global energy system emissions to be halved by 2050 and complete decarbonization by 2100. In the nationally orientated climate policy framework codified under the Paris Agreement, each nation must decide the scale and method of their emissions reduction contribution while remaining consistent with the global carbon budget. This policy process will require engagement amongst a wide range of stakeholders who have very different visions for the physical implementation of deep decarbonization. The Deep Decarbonization Pathways Project (DDPP) has developed a methodology, building on the energy, climate and economics literature, to structure these debates based on the following principles: country-scale analysis to capture specific physical, economic and political circumstances to maximize policy relevance, a long-term perspective to harmonize short-term decisions with the long-term objective and detailed sectoral analysis with transparent representation of emissions drivers through a common accounting framework or ‘dashboard’. These principles are operationalized in the creation of deep decarbonization pathways (DDPs), which involve technically detailed, sector-by-sector maps of each country’s decarbonization transition, backcasting feasible pathways from 2050 end points. This article shows how the sixteen DDPP country teams, covering 74% of global energy system emissions, used this method to collectively restrain emissions to a level consistent with the 2 °C target while maintaining development aspirations and reflecting national circumstances, mainly through efficiency, decarbonization of energy carriers (e.g. electricity, hydrogen, biofuels and synthetic gas) and switching to these carriers. The cross-cutting analysis of country scenarios reveals important enabling conditions for the transformation, pertaining to technology research and development, investment, trade and global and national policies. Policy relevance In the nation-focused global climate policy framework codified in the Paris Agreement, the purpose of the DDPP and DDPs is to provide a common method by which global and national governments, business, civil society and researchers in each country can communicate, compare and debate differing concrete visions for deep decarbonization in order to underpin the necessary societal and political consensus to design and implement short-term policy packages that are consistent with long-term global decarbonization.

The Deep Decarbonization Pathways Project (DDPP): insights and emerging issues

International climate policy discussions have fundamentally changed since the fifteenth Conference of the Parties (COP 15) in Copenhagen. Before, the debate was organized around short-term, incremental actions and common but differentiated responsibility (CBDR) was interpreted as putting the responsibility for action on developed countries. Since then, international negotiations have evolved under the increasing pressure from scientific evidence of the negative development impacts of climate change drivers and outcomes (e.g. coal combustion air pollution and sea level rise) and of the increasingly stringent mitigation requirements for climate stabilization. This resulted in international agreement to limit the mean surface temperature increase to 2°C compared with pre-industrial levels, as formalized in the Cancun COP 16 agreement, and recognition that formal participation by all major emitters would be required, as formalized in the Durban COP 17 agreement that each nation would offer voluntary national low-carbon development strategies. These are now called Intended Nationally Determined Contributions (INDCs).

Incorporating land-use requirements and environmental constraints in low-carbon electricity planning for California.

The land-use implications of deep decarbonization of the electricity sector (e.g., 80% below 1990 emissions) have not been well-characterized quantitatively or spatially. We assessed the operational-phase land-use requirements of different low-carbon scenarios for California in 2050 and found that most scenarios have comparable direct land footprints. While the per MWh footprint of renewable energy (RE) generation is initially higher, that of fossil and nuclear generation increases over time with continued fuel use. We built a spatially explicit model to understand the interactions between resource quality and environmental constraints in a high RE scenario (>70% of total generation). We found that there is sufficient land within California to meet the solar and geothermal targets, but areas with the highest quality wind and solar resources also tend to be those with high conservation value. Development of some land with lower conservation value results in lower average capacity factors, but also provides opportunity for colocation of different generation technologies, which could significantly improve land-use efficiency and reduce permitting, leasing, and transmission infrastructure costs. Basing siting decisions on environmentally-constrained long-term RE build-out requirements produces significantly different results, including better conservation outcomes, than implied by the current piecemeal approach to planning.

Publisher Correction: Measuring progress from nationally determined contributions to mid-century strategies

In the version of this Article previously published, technical problems led to the wrong summary appearing on the homepage, and an incorrect Supplementary Information file being uploaded. Both errors have now been corrected.