2009; Cohen et al. 2010; Stephens et al. 2008). Without doubt, these transitions must be guided by an ethics that brings together technology and sustainability. In the introductory message to this special issue,
Jean-Louis Armand calls for such an ethic of long-range responsibility—one that is properly embedded in sustainability science as a guide for our future. In see more response to this complex issue, Sustainability Science has organized a special issue on two related themes—the costs of mitigating greenhouse gas (GHG) emissions and the diffusion of clean energy technologies. The first four papers model abatement costs for world regions and sectors with a focus on medium term GHG emission targets (2020 and 2030)—a key step in stabilizing long-term BKM120 in vitro climate change under the United Nations Framework Convention on Climate Change (UNFCCC). These studies find that transitions toward a low-carbon society are not an extension of the current trends, and far greater GHG reductions—both on national and global scales—are required in the mid-term. A further five papers explore the barriers and opportunities of energy transitions on the ground, using transition management theories to explain empirical cases in India, Japan, Malaysia and the United States. Hanaoka and Kainuma conduct a comparison of GHG marginal abatement cost (MAC) curves from 0 to 200 US $/tCO2eq in 2020 and 2030 with engineering-based
‘bottom up’ models covering major countries. The study finds that there are great differences in the technological feasibility of GHG mitigation between world regions and models, giving a wide spread of results. Future portfolios of advanced technologies and energy resources,
especially nuclear and renewable energies, are the most prominent reasons for these differences. Akashi and Hanaoka use a bottom-up model named AIM/Enduse[Global]—part of the Asia-Pacific Integrated model (AIM)—to investigate the technological feasibility and costs of global 50 % emissions reductions by 2050 relative to 1990 levels. They find that such a major reduction is feasible with marginal costs of US $150/tCO2eq in 2020 and up to US $600/tCO2eq in 2050. Renewables, fuel switching and efficiency improvements in power generation account for 45 % of the total emissions reductions in 2020, while carbon dioxide capture and storage (CCS) and renewables account Montelukast Sodium for a full 64 % of reduction potential by 2050. Akimoto and colleagues then explore GHG emissions reduction potentials across world regions and sectors using the Dynamic New Earth 21 (DNE21+) model for energy-related emissions and a non-CO2 assessment model for other emissions. Taking fossil fuel prices based on the International Energy Agency World Energy Outlook 2010 reference scenario as a baseline and considering a short payback time, the analysis finds that, with relatively low carbon costs below US $50/tCO2eq, the reduction potentials in SN-38 UNFCCC non-Annex 1 countries, including India and China, are large.