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Achieving climate policy targets will require large-scale deployment of low-carbon energy technologies, including nuclear power. The small modular reactor (SMR) is viewed as a possible solution to the problems of energy security as well as climate change. In this paper, we use an integrated assessment model (IAM) to investigate the evolution of a global energy portfolio with SMRs under a stringent climate policy. Technology selection in the model is based on costs; we use results from previous expert elicitation studies of SMR costs. We find that the costs of achieving a 2 °C target are lower with SMRs than without. The costs are higher when large reactors do not compete for market share compared to a world in which they can compete freely. When both SMRs and large reactors compete for market share, reduction in mitigation cost is achieved only under advanced assumptions about SMR technology costs and future cost improvements. While the availability of SMRs could lower mitigation costs by a moderate amount, actual realization of these benefits would depend on the rapid up-scaling of SMRs in the near term. Such rapid deployment could be limited by several social, institutional and behavioral obstacles.

Improving the energy efficiency of building stock, commercial equipment, and household appliances can have a major positive impact on energy use, carbon emissions, and building services. Sub-national regions such as the U.S. states wish to increase energy efficiency, reduce carbon emissions, or adapt to climate change. Evaluating sub-national policies to reduce energy use and emissions is difficult because of the large uncertainties in socioeconomic factors, technology performance and cost, and energy and climate policies. Climate change itself may undercut such policies. However, assessing all of the uncertainties of large-scale energy and climate models by performing thousands of model runs can be a significant modeling effort with its accompanying computational burden. By applying fractional–factorial methods to the GCAM-USA 50-state integrated-assessment model in the context of a particular policy question, this paper demonstrates how a decision-focused sensitivity analysis strategy can greatly reduce computational burden in the presence of uncertainty and reveal the important drivers for decisions and more detailed uncertainty analysis.

We explore the implications that alternative pathways for human population and economic development have for the role of Asia in reference no-climate-policy scenarios and scenarios in which climate forcing is limited. We consider three different pathways of socioeconomic development, which we refer to as Shared Socio-economic Pathways (SSPs) and four different levels of limitation on climate forcing, which we refer to as Shared Climate Policy Assumptions (SPAs). SSPs are differentiated by population and economic growth assumptions, while SPAs are differentiated on the level of radiative forcing in the year 2100. Regardless of the scenarios we examined Asia plays a central role in shaping the world's future with nearly half of the world's people and more than half of the world's economic activity and energy consumption. The future of Asia and the world are dramatically different across the various combinations of SSPs and SPAs. High population worlds place significant stress on Asian resources and ecosystems. In high population SSPs the poorest members of the population face high energy and food prices and the more stringent the level of emissions mitigation, the more stress poor populations experience, though the more stringent the emissions mitigation, the larger the area of unmanaged ecosystems that are preserved.

The EMF22 Transition Scenario subgroup explores the implications of delayed accession on limiting climate change to various radiative forcing levels. This paper focuses on the cost of limiting radiative forcing and the role that industrial leakage plays in scenarios of delayed accession. We find that delayed participation shifts the cost burden toward regions that take early action and away from regions that undertake mitigation later. However, the inefficiencies introduced by delay are so great that present discounted costs are higher in the delayed scenario for regions that delay as well as for regions taking early actions. An important element of these inefficiencies is industrial emissions leakage, that is non-participating regions increase their emissions relative to the reference case. In aggregate, industrial leakage rates are less than 10% if all regions of the world begin emissions mitigation by 2050—higher in carbon-intensive sectors and lower in low-carbon-intensity sectors. Additionally, we consider the implication of technology on carbon prices, the feasibility of limiting radiative forcing to low levels, and the incentives to overshoot the radiative forcing limit.

This paper, a contribution to the EMF 22 subgroup on Transition Scenarios, examines the relationship between technology evolution over the next 40 years and the cost, energy, and greenhouse gas emissions consequences of possible U.S. mitigation goals. The paper explores these issues within the context of cumulative emissions targets based on linear reductions in CO 2 -e emissions of 50% and 80% below 1990 levels by 2050. Six technology futures were constructed within the MiniCAM integrated assessment model and then applied to the emissions targets. The paper explores the influence of technology availability and expectations of future technology availability on the economic consequences of emissions mitigation, on the time path of emissions mitigation, and on the evolution of the U.S. energy system over time. One of the strongest themes to emerge from the scenarios in this study is that near-term decision-making depends on the availability of technology decades into the future, when deep emissions reductions are required to meet the cumulative emissions goals. In the scenarios in this paper, it is the expectations about future technology that have the most dramatic effect on greenhouse gas emissions prices and emissions reductions in 2020, as opposed to near-term technology availability. Moreover, it is the nature of technology 20, 30, and 40 years out, rather than availability and deployment of technology in the next decade, that will largely determine the character of the mid-century energy system.

The EMF 22 subgroup on Transition Scenarios explores a rich suite of potential future worlds in which climate change is limited to a variety of alternative radiative forcing levels. This paper focuses primarily on the requirements to limit radiative forcing from Kyoto gases to 2.6 W/m2. Given that we estimate year 2005 radiative forcing to be 2.4 W/m2, the 2.6 W/m2 limit creates a non-trivial constraint. Allowing radiative forcing to exceed the long-term target level provides greater latitude in achieving the goal, but implies major changes to both global energy and land-use systems in the near term as well as the long term. In addition, delay on the part of major emitting parties creates potential “leakage” in both energy and land use. We estimate the challenging near-term and long-term deployment of new wind power, nuclear power and CO2 capture and storage associated with the 2.6 W/m2 limit.

We examine the potential role of several energy technologies, including carbon capture and dispose (CC and D), hydrogen and advanced transportation systems, on the cost of stabilizing CO2 concentrations. While not currently deployed at scale, CC and D, hydrogen energy systems, and biotechnology have the potential to be major components of the global energy system by the middle of the 21st century. Other technologies, such as renewables, nuclear power and energy efficiency also play critical roles in addressing climate change. The development of advanced technologies in the absence of limitations on the concentration of carbon dioxide need not lead to CO2 stabilization.

Using the Indian module of the Second Generation Model (SGM), we explore a reference case and three scenarios in which greenhouse gas emissions were controlled. Two alternative policy instruments (carbon taxes and tradable permits) were analyzed to determine comparative costs of stabilizing emissions at (1) 1990 levels (the 1X case), (2) two times the 1990 levels (the 2X case), and (3) three times the 1990 levels (the 3X case). The analysis takes into account India's rapidly growing population and the abundance of coal and biomass relative to other fuels. We also explore the impacts of a global tradable permits market to stabilize global carbon emissions on the Indian economy under the following two emissions allowance allocation methods. 1. 1. Grandfathered emissions: emissions allowances are allocated based on 1990 emissions. 2. 2. Equal per capita emissions: emissions allowances are allocated based on share of global population. Tradable permits represent a lower-cost method to stabilize Indian emissions than carbon taxes, i.e. global action would benefit India more than independent actions.