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This research links the Integrated MARKAL-EFOM system model of China (China TIMES) and the Greenhouse Gas and Air Pollution Interactions and Synergies model (GAINS) to assess the co-benefits of air quality improvement under the Nationally Determined Contribution (NDC) and the well below 2 °C (WBD2) target. Results show that the industry sector and power sector are the key sources necessary to reduce air pollutant emissions, mainly due to the phasing out of fossil fuels. The electrification in the building sector will be another main source by which to decrease PM 2.5 emissions. The adoption of various low-carbon constraints and further air pollutant control strategies will significantly alleviate the current air pollution problems in China by reducing the concentration and scope of the air pollutants and reducing the corresponding number of premature deaths. A stricter air pollutant control strategy will lead to increases in air pollutant control costs; however, the low-carbon targets will help reduce these costs in the long run. Compared to the current national policy, within the same air pollutant control strategy, the reduction of air pollutant control cost can cover the incremental CO 2 mitigation cost under the NDC target, while this cannot be realized under the WBD2 target.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.techfore.2006.05.026 Byline: Keywan Riahi (a), Arnulf Grubler (a)(b), Nebojsa Nakicenovic (a)(c) Abstract: This paper presents an overview of the greenhouse gas (GHG) emissions scenarios that form the analytical backbone for other contributions to this Special Issue. We first describe the motivation behind this scenario exercise and introduce the main scenario features and characteristics, in both qualitative and quantitative terms. Altogether, we analyze three 'baseline' scenarios of different socio-economic and technological developments that are assumed not to include any explicit climate policies. We then impose a range of climate stabilization targets on these baseline scenarios and analyze in detail the feasibility, costs and uncertainties of meeting a range of different climate stabilization targets in accordance with Article 2 of the United Nations Framework Convention on Climate Change. The scenarios were developed by the IIASA Integrated Assessment Modeling Framework that encompasses detailed representations of the principal GHG-emitting sectors -- energy, industry, agriculture, and forestry. The main analytical findings from our analysis focus on the implications of salient uncertainties (associated with scenario baselines and stabilization targets), on feasibility and costs of climate stabilization efforts, and on the choice of appropriate portfolios of emissions abatement measures. We further analyze individual technological options with regards to their aggregated cumulative contribution toward emissions mitigation during the 21st century as well as their deployment over time. Our results illustrate that the energy sector will remain by far the largest source of GHG emissions and hence remain the prime target of emissions reduction. Ultimately, this may lead to a complete restructuring of the global energy system. Climate mitigation could also significantly change the relative economics of traditional versus new, more climate friendly products and services. This is especially the case within the energy system, which accounts for the largest share of emissions reductions, but it is also the case in the agriculture and forestry sectors, where emissions reduction and sink enhancement measures are relatively more modest. Author Affiliation: (a) Transitions to New Technologies Program, International Institute for Applied Systems Analysis, Laxenburg, Austria (b) School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA (c) Department of Power Systems and Energy Economics, Technical University Vienna, Austria Article History: Received 4 March 2006; Revised 10 March 2006; Accepted 24 May 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.techfore.2006.05.024 Byline: Ilkka Keppo (a), Brian C. O'Neill (a)(b), Keywan Riahi (a) Keywords: Climate change; Energy modeling; Climate sensitivity; Uncertainty analysis Abstract: This paper explores the implications for global average temperature change of a set of reference and mitigation scenarios in a probabilistic framework. First, we use published probability density functions for climate sensitivity to investigate the likelihood of achieving targets expressed as levels or rates of global average temperature change. We find, for example, that limiting warming to 3 C above pre-industrial levels with at least a medium likelihood requires cumulative emissions reductions on the order of 30-60% below one unmitigated reference scenario by 2100, while a more favorable baseline scenario requires no reductions at all to achieve this outcome with the same likelihood. We further conclude that the rate of temperature change may prove to be more difficult to control, especially if most of the mitigation effort is postponed until later in the century. Rate of change targets of 0.1-0.2 [degrees]C/decade are unlikely to be achieved by a target for the long-term level of climate change alone. Second, we quantify relationships between mitigation costs and the likelihood of achieving various targets and show how this depends strongly on the reference scenario. Third, we explore relationships between medium-term achievements and long-term climate change outcomes. Our results suggest that atmospheric concentrations and the share of zero-carbon energy in the middle of the 21st century are key indicators of the likelihood of meeting long-term climate change goals cost-effectively. They also suggest that interim targets could be an effective means of keeping long-term target options open. Our analysis shows that least-cost mitigation strategies for reaching low climate change targets include a wide portfolio of reduction measures. In particular, fundamental long-term structural changes in the energy system in these scenarios are a necessary but not sufficient condition to achieve high likelihoods for low temperature targets. The cost-effective portfolio of emissions reductions must also address demand-side measures and include mitigation options in the industry, agriculture, and the forest sector. Author Affiliation: (a) International Institute for Applied Systems Analysis, Laxenburg, Austria (b) Watson Institute for International Studies, Brown University, Providence, RI, USA Article History: Received 7 February 2006; Revised 14 May 2006; Accepted 24 May 2006

Emissions of air pollutants such as sulfur and nitrogen oxides and particulates have significant health impacts as well as effects on natural and anthropogenic ecosystems. These same emissions also can change atmospheric chemistry and the planetary energy balance, thereby impacting global and regional climate. Long-term scenarios for air pollutant emissions are needed as inputs to global climate and chemistry models, and for analysis linking air pollutant impacts across sectors. In this paper we present methodology and results for air pollutant emissions in Shared Socioeconomic Pathways (SSP) scenarios. We first present a set of three air pollution narratives that describe high, central, and low pollution control ambitions over the 21st century. These narratives are then translated into quantitative guidance for use in integrated assessment models. The resulting pollutant emission trajectories under the SSP scenarios cover a wider range than the scenarios used in previous international climate model comparisons. In the SSP3 and SSP4 scenarios, where economic, institutional and technological limitations slow air quality improvements, global pollutant emissions over the 21 st century can be comparable to current levels. Pollutant emissions in the SSP1 scenarios fall to low levels due to the assumption of technological advances and successful global action to control emissions. [ABSTRACT FROM AUTHOR]

This paper compares projections over the twenty-first century of SO, BC, and OC emissions from three technologically detailed, long-term integrated assessment models. The character of the projections and the response of emissions due to a comprehensive climate policy are discussed focusing on the sectoral level. In a continuation of historical experience, aerosol and precursor emissions are increasingly decoupled from carbon dioxide emissions over the twenty-first century due to a combination of emission controls and technology shifts over time. Implementation of a comprehensive climate policy further reduces emissions, although there is significant variation in this response by sector and by model: the response has many similarities between models for the energy transformation and transportation sectors, with more diversity in the response for the building and industrial sectors. Much of these differences can be traced to specific characteristics of reference case end-use and supply-side technology deployment and emissions control assumptions, which are detailed by sector. [ABSTRACT FROM AUTHOR]

Climate policies must consider radiative forcing from Kyoto greenhouse gases, as well as other forcing constituents, such as aerosols and tropospheric ozone that result from air pollutants. Non-Kyoto forcing constituents contribute negative, as well as positive forcing, and overall increases in total forcing result in increases in global average temperature. Non-Kyoto forcing modeling is a relatively new component of climate management scenarios. This paper describes and assesses current non-Kyoto radiative forcing modeling within five integrated assessment models. The study finds negative forcing from aerosols masking (offsetting) approximately 25 % of positive forcing in the near-term in reference non-climate policy projections. However, masking is projected to decline rapidly to 5-10 % by 2100 with increasing Kyoto emissions and assumed reductions in air pollution-with the later declining to as much as 50 % and 80 % below today's levels by 2050 and 2100 respectively. Together they imply declining importance of non-Kyoto forcing over time. There are however significant uncertainties and large differences across models in projected non-Kyoto emissions and forcing. A look into the modeling reveals differences in base conditions, relationships between Kyoto and non-Kyoto emissions, pollution control assumptions, and other fundamental modeling. In addition, under climate policy scenarios, we find air pollution and resulting non-Kyoto forcing reduced to levels below those produced by air pollution policies alone-e.g., China sulfur emissions fall an additional 45-85 % by 2050. None of the models actively manage non-Kyoto forcing for climate implications. Nonetheless, non-Kyoto forcing may be influencing mitigation results, including allowable carbon dioxide emissions, and further evaluation is merited. [ABSTRACT FROM AUTHOR]

Highlights: [•] Current air quality policies will be inadequate in achieving reductions in global air pollution. [•] Energy access policies will be vital to achieve improvements in global outdoor air quality. [•] Integrating policies on pollution, climate change and energy access leads to compliance with WHO levels. [•] Significant health benefits and cost savings result from integrated policies. [ABSTRACT FROM AUTHOR]

Reaching the economic, environmental and sustainability objectives of all societies requires overcoming several major energy challenges; it necessitates rapid progress in multiple areas. The scenario pathways presented in this paper describe transformative changes toward these goals, taking a broad view of the four main energy challenges faced by society in the 21st century: providing universal access to modern energy for all; reducing the impacts of energy production on human health and the environment; avoiding dangerous climate change; and enhancing energy security. The overarching objective of the paper is to provide policy guidance on how to facilitate the transformation of the energy system to achieve these multiple energy objectives. Particular focus is given to the required pace of the transformation at both the global and regional levels, and to the types of financial and policy measures that will be needed to ensure a successful transition. Synergies and trade-offs between the objectives are identified, and co-benefits quantified. The paper makes an important contribution to the scenario literature by approaching the global transition toward sustainable development in a more integrated, holistic manner than is common in other studies. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides the background and the context for the analyses presented in the seven papers of this Special Issue on Integrated Assessment of Uncertainties in Greenhouse Gas Emissions and their Mitigation. First, the main topic and content of the Special Issue is given, followed by an overall overview. Second, detailed overviews and summaries of the seven papers are given. The specific analytical and methodological features and findings of each paper are highlighted and the linkages between the various papers presented in the Special Issue are provided. [Copyright &y& Elsevier]

This paper examines the role of technological change and spillovers within the context of a climate policy in a long-term scenario of the global energy system. We use the energy-systems optimization model MESSAGE considering endogenous learning for various technologies, such that they experience cost reductions as a function of accumulated capacity installations. We find that the existence of technological learning while reducing overall energy system costs becomes particularly important in the context of a long-term climate policy. Diversity in technological portfolios is emphasized and results indicate deployment of a range of energy technologies in reducing emissions. An important finding is that technological learning by itself is not sufficient for climate stabilization and that climate policies are an absolute necessary complimentary element. Under a climate constraint, spillovers across technologies and regions due to learning results in increased upfront investments and hence lower costs of carbon free technologies, thus resulting in technology deployment and emissions reductions, especially in developing countries. We conclude that learning and spillover effects can lead to technologically advanced cost-effective global energy transition pathways. We suggest that coordinated climate stabilization policies can serve as important institutional mechanisms that facilitate the required technological investments, especially in developing countries and thus ensure long-term cost reductions. [ABSTRACT FROM AUTHOR]

This article assesses emissions scenarios in the literature, originally documented in the scenario database that was developed more than 7 years ago. The original scenario assessment and literature review has been used, among other things, as the basis for the quantification of the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) reference scenarios and the IPCC Third Assessment Report (TAR) stabilization scenarios. In the meantime, a large number of new emissions scenarios have been developed and published. We have collected the relevant information about these new scenarios with the objective to assess the more recent perspectives about future global emissions and to assess the changes in the perspectives about future emissions and their driving forces that may have occurred since the publication of SRES and TAR scenarios. Our analysis goes beyond mere comparisons of emissions ranges. In particular, we explore the underlying drivers of emissions using the so-called IPAT identity (Impacts are proportional to the product of Population, Affluence, and Technology). When IPAT analysis refers to carbon emissions it is called the Kaya identity, where carbon dioxide (CO2) emissions are assumed to correspond to the product of population, per capita income, energy intensity of gross domestic product (GDP), and CO2 intensity of energy. Comparing the recent scenario literature with the scenarios developed before TAR shows that there are strong similarities for the main underlying tendencies in many of the scenario's driving forces and results. [ABSTRACT FROM AUTHOR]

This paper analyzes potentials of carbon capture and sequestration technologies (CCS) in a set of long-term energy-economic-environmental scenarios based on alternative assumptions for technological progress of CCS. In order to get a reasonable guide to future technological progress in managing CO2 emissions, we review past experience in controlling sulfur dioxide emissions (SO2) from power plants. By doing so, we quantify a “learning curve” for CCS, which describes the relationship between the improvement of costs due to accumulation of experience in CCS construction. We incorporate the learning curve into the energy modeling framework MESSAGE-MACRO and develop greenhouse gas emissions scenarios of economic, demographic, and energy demand development, where alternative policy cases lead to the stabilization of atmospheric CO2 concentrations at 550 parts per million by volume (ppmv) by the end of the 21st century. Due to the assumed technological learning, costs of the emissions reduction for CCS drop rapidly and in parallel with the massive introduction of CCS on the global scale. Compared to scenarios based on static cost assumptions for CCS, the contribution of carbon sequestration is about 50 percent higher in the case of learning resulting in cumulative sequestration of CO2 ranging from 150 to 250 billion (109) tons carbon during the 21st century. The results illustrate that carbon capture and sequestration is one of the obvious priority candidates for long-term technology policies and enhanced R&D efforts to hedge against the risk associated with high environmental impacts of climate change. [Copyright &y& Elsevier]

Emissions harmonization refers to the process used to match greenhouse gas (GHG) and air pollutant results from Integrated Assessment Models (IAMs) against a common source of historical emissions. To date, harmonization has been performed separately by individual modeling teams. For the hand-over of emission data for the Shared Socioeconomic Pathways (SSPs) to climate model groups, a new automated approach based on commonly agreed upon algorithms was developed. This work describes the novel methodology for determining such harmonization methods and an open-source Python software library implementing the methodology. A case study is presented for two example scenarios (with and without climate policy cases) using the IAM MESSAGE-GLOBIOM that satisfactorily harmonize over 96% of the total emissions trajectories while having a negligible effect on key long-term climate indicators. This new capability enhances the comparability across different models, increases transparency and robustness of results, and allows other teams to easily participate in intercomparison exercises by using the same, openly available harmonization mechanism. [ABSTRACT FROM AUTHOR]