Search

This chapter focuses on accelerating mitigation and on shifting development pathways to increased sustainability, based on literature particularly at national scale. While previous WGIII assessments have discussed mitigation pathways, focus on development pathways is more recent. The timeframe is the near term (now up to 2030) to mid-term (2030 to 2050), complementing Chapter 3 on the long term (from 2050 onward).

National-level climate actions will be vital in achieving global temperature goals in the coming decades. Near-term (2025–2030) plans are laid out in Nationally Determined Contributions; the next step is the submission of long-term strategies for 2050. At present, national scenarios underpinning long-term strategies are poorly coordinated and incompatible across countries, preventing assessment of individual nations’ climate policies. Here we present a systematic and standardized, yet flexible, scenario framework varying 2050 emissions to build long-term national energy and climate mitigation scenarios. Applying the framework to six major Asian countries reveals individual challenges in energy system transformation and investment needs in comparable scenarios. This framework could be a starting point for comprehensive assessments as input to the Global Stocktake over the coming years.

Climate change is expected to increase the frequency, intensity and spatial extent of extreme climate events, and thus is a key concern for food production. However, food insecurity is usually analysed under a mean climate change state. Here we combine crop modelling and climate scenarios to estimate the effects of extreme climate events on future food insecurity. Relative to median-level climate change, we find that an additional 20–36% and 11–33% population may face hunger by 2050 under a once-per-100-yr extreme climate event under high and low emission scenarios, respectively. In some affected regions, such as South Asia, the amount of food required to offset such an effect is triple the region’s current food reserves. Better-targeted food reserves and other adaptation measures could help fill the consumption gap in the face of extreme climate variability.

This study assesses Japan’s mid-century low-emission pathways using both national and global integrated assessment models in the common mitigation scenario framework, based on the carbon budgets corresponding to the global 2 °C goal. We examine high and low budgets, equal to global cumulative 1600 and 1000 Gt-CO2 (2011–2100) for global models, and 36 and 31 Gt-CO2 (2011–2050) in Japan for national models, based on the cost-effectiveness allocation performed by the global models. The impacts of near-term policy assumption, including the implementation and enhancement of the 2030 target of the nationally determined contribution (NDC), are also considered. Our estimates show that the low budget scenarios require a 75% reduction of CO2 emissions by 2050 below the 2010 level, which is nearly the same as Japan’s governmental 2050 goal of reducing greenhouse gas emissions by 80%. With regard to near-term actions, Japan’s 2030 target included in the NDC is on track to meet the high budget scenario, whereas it is falling short for the low budget scenario, which would require emission reductions immediately after 2020. Whereas models differ in the type of energy source on which they foresee Japan basing its decarbonization process (e.g., nuclear- or variable renewable energy-dependent), the large-scale deployment of low-carbon energy (nuclear, renewable, and carbon capture and storage) is shared across most models in both the high and low budget scenarios. By 2050, low-carbon energy represents 44–54% of primary energy and 86–97% of electricity supply in the high and low budget scenarios, respectively.

The Paris Agreement set long-term global climate goals to pursue stabilization of the global mean temperature increase at below 2 °C (the so-called 2 °C goal). Individual countries submitted their own short-term targets, mostly for the year 2030. Meanwhile, the UN's sustainable development goals (SDGs) were designed to help set multiple societal goals with respect to socioeconomic development, the environment, and other issues. Climate policies can lead to intended or unintended consequences in various sectors, but these types of side effects rarely have been studied in China, where climate policies will play an important role in global greenhouse gas emissions and sustainable development is a major goal. This study identified the extent to which climate policies in line with the 2 °C goal could have multi-sectoral consequences in China. Carbon constraints in China in the 2Deg scenario are set to align with the global 2 °C target based on the emissions per capita convergence principle. Carbon policies for NDC pledges as well as policies in China regarding renewables, air pollution control, and land management were also simulated. The results show that energy security and air quality have co-benefits related to climate policies, whereas food security and land resources experienced negative side effects (trade-offs). Near-term climate actions were shown to help reduce these trade-offs in the mid-term. A policy package that included food and land subsidies also helped achieve climate targets while avoiding the adverse side effects caused by the mitigation policies. The findings should help policymakers in China develop win–win policies that do not negatively affect some sectors, which could potentially enhance their ability to take climate actions to realize the global 2 °C goal within the context of sustainable development.

The Paris Agreement has confirmed that the ultimate climate policy goal is to hold the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the increase to 1.5 °C. Moving the goal from 2 °C to 1.5 °C calls for much more concerted effort, and presents greater challenges and costs. This study uses an Asia-Pacific Integrated Model/Computable General Equilibrium (AIM/CGE) to evaluate the role of socioeconomic factors (e.g. technological cost and energy demand assumptions) in changing mitigation costs and achieving the 1.5 °C and 2 °C goals, and to identify the channels through which socioeconomic factors affect mitigation costs. Four families of socioeconomic factors were examined, namely low-carbon energy-supply technologies, end-use energy-efficiency improvements, lifestyle changes and biomass-technology promotion (technology cost reduction and social acceptance promotion). The results show that technological improvement in low-carbon energy-supply technologies is the most important factor in reducing mitigation costs. Moreover, under the constraints of the 1.5 °C goal, the relative effectiveness of other socioeconomic factors, such as energy efficiency improvement, lifestyle changes and biomass-related technology promotion, becomes more important in decreasing mitigation cost in the 1.5 °C scenarios than in the 2 °C scenarios.

This article summarizes the recent activity of the International Stem Cell Banking Initiative (ISCBI) held at the California Institute for Regenerative Medicine (CIRM) in California (June 26, 2016) and the Korean National Institutes for Health in Korea (October 19-20, 2016). Through the workshops, ISCBI is endeavoring to support a new paradigm for human medicine using pluripotent stem cells (hPSC) for cell therapies. Priority considerations for ISCBI include ensuring the safety and efficacy of a final cell therapy product and quality assured source materials, such as stem cells and primary donor cells. To these ends, ISCBI aims to promote global harmonization on quality and safety control of stem cells for research and the development of starting materials for cell therapies, with regular workshops involving hPSC banking centers, biologists, and regulatory bodies. Here, we provide a brief overview of two such recent activities, with summaries of key issues raised. Stem Cells Translational Medicine 2017;6:1956-1962.

Energy is crucial for supporting basic human needs, development and well-being. The future evolution of the scale and character of the energy system will be fundamentally shaped by socioeconomic conditions and drivers, available energy resources, technologies of energy supply and transformation, and end-use energy demand. However, because energy-related activities are significant sources of greenhouse gas (GHG) emissions and other environmental and social externalities, energy system development will also be influenced by social acceptance and strategic policy choices. All of these uncertainties have important implications for many aspects of economic and environmental sustainability, and climate change in particular. In the Shared-Socioeconomic Pathway (SSP) framework these uncertainties are structured into five narratives, arranged according to the challenges to climate change mitigation and adaptation. In this study we explore future energy sector developments across the five SSPs using Integrated Assessment Models (IAMs), and we also provide summary output and analysis for selected scenarios of global emissions mitigation policies. The mitigation challenge strongly corresponds with global baseline energy sector growth over the 21st century, which varies between 40% and 230% depending on final energy consumer behavior, technological improvements, resource availability and policies. The future baseline CO2-emission range is even larger, as the most energy-intensive SSP also incorporates a comparatively high share of carbon-intensive fossil fuels, and vice versa. Inter-regional disparities in the SSPs are consistent with the underlying socioeconomic assumptions; these differences are particularly strong in the SSPs with large adaptation challenges, which have little inter-regional convergence in long-term income and final energy demand levels. The scenarios presented do not include feedbacks of climate change on energy sector development. The energy sector SSPs wit

This study contributes to the realization of intended nationally determined contributions (INDCs) by analyzing their implications for the energy production system and the economy and determines the role of renewable energies (RE) in reducing the challenge of committing to the INDCs. The Asia-Pacific Integrated Model/Computable General Equilibrium (AIM/CGE) model was used to assess seven scenarios having the same socioeconomic development but different shares of RE in power generation. By comparing different relative reductions caused by the emission constraints vis-a-vis the business-as-usual (BaU) scenario, the mitigation costs can be estimated. Results show that the economic impact could be reduced by around 55% in terms of welfare loss (from 6.0 to 2.7%) and by around 36% in terms of gross domestic product (GDP) loss (from 3.4 to 2.1%) through the incorporation of high levels of renewable energy. Furthermore, the additional double deployment of wind and SPV to 5.4% and 12.0%, respectively, which currently comprise 43.1% of the renewable energies used in electricity generation, could reduce the GDP loss from 2.1 to 1.9% and reduce the welfare loss from 2.7 to 1.5% in order to achieve a 25.0% GHG emissions reduction. These losses are less than those in the pricing-only scenario (2.1% and 2.3%, respectively).

Thailand had summited its Intended Nationally Determined Contributions (INDCs) in 2015 and ratified the Paris Agreement in September 2016. Its INDCs stated that by 2030 GHG emissions will be reduced by 20–25% when compared to the business-as-usual (BAU) scenario by using mainly domestic renewable energy resources and energy efficiency improvement. Therefore, this paper assesses the potential of greenhouse gas (GHG) emission reduction by the use of renewable energy in Thailand's INDCs and the economic impacts from GHG emission reduction. This paper employed the Asia-Pacific Integrated Model/Computable General Equilibrium (AIM/CGE). Besides the BAU scenario, four mitigation scenarios are assessed at given GHG emission levels and renewable power generation targets. Results show that Thailand's INDC can be achieved under the current renewable energy target in Thailand's Power Development Plan 2015. As a result, macroeconomic loss will be small under the light GHG reduction target; however, it will be large under the stringent GHG emission reduction target. The GDP loss ranges from 0.2% in the case of a 20% reduction target to 3.1% in the case of a 40% reduction target in 2030. Thus, the availability of land for deploying the renewable energy technologies such as solar, wind and biomass needs to be assessed.

The exposure of workers to hot environments is expected to increase as a result of climate change. In order to prevent heat-related illness, it is recommended that workers take breaks during working hours. However, this would lead to reductions in worktime and labor productivity. In this study, we estimate the economic cost of heat-related illness prevention through worker breaks associated with climate change under a wide range of climatic and socioeconomic conditions. We calculate the worktime reduction based on the recommendation of work/rest ratio and the estimated future wet bulb glove temperature, which is an index of heat stresses. Corresponding GDP losses (cost of heat-related illness prevention through worker breaks) are estimated using a computable general equilibrium model throughout this century. Under the highest emission scenario, GDP losses in 2100 will range from 2.6 to 4.0% compared to the current climate conditions. On the other hand, GDP losses will be less than 0.5% if the 2.0 °C goal is achieved. The benefit of climate-change mitigation for avoiding worktime loss is comparable to the cost of mitigation (cost of the greenhouse gas emission reduction) under the 2.0 °C goal. The relationship between the cost of heat-related illness prevention through worker breaks and global average temperature rise is approximately linear, and the difference in economic loss between the 1.5 °C goal and the 2.0 °C goal is expected to be approximately 0.3% of global GDP in 2100. Although climate mitigation and socioeconomic development can limit the vulnerable regions and sectors, particularly in developing countries, outdoor work is still expected to be affected. The effectiveness of some adaptation measures such as additional installation of air conditioning devices or shifting the time of day for working are also suggested. In order to reduce the economic impacts, adaptation measures should also be implemented as well as pursing ambitious climate change mitigatio

This study analyzed the role of low-carbon energy technologies in reducing the greenhouse gas emissions of Indonesia’s energy sector by 2030. The aim of this study was to provide insights into the Indonesian government’s approach to developing a strategy and plan for mitigating emissions and achieving Indonesia’s emission reduction targets by 2030, as pledged in the country’s Intended Nationally Determined Contribution. The Asia-Pacific Integrated Model/Computable General Equilibrium (AIM/CGE) model was used to quantify three scenarios that had the same socioeconomic assumptions: baseline, countermeasure (CM)1, and CM2, which had a higher emission reduction target than that of CM1. Results of the study showed that an Indonesian low-carbon energy system could be achieved with two pillars, namely, energy efficiency measures and deployment of less carbon-intensive energy systems (i.e., the use of renewable energy in the power and transport sectors, and the use of natural gas in the power sector and in transport). Emission reductions would also be satisfied through the electrification of end-user consumption where the electricity supply becomes decarbonized by deploying renewables for power generation. Under CM1, Indonesia could achieve a 15.5% emission reduction target (compared to the baseline scenario). This reduction could be achieved using efficiency measures that reduce final energy demand by 4%; This would require the deployment of geothermal power plants at a rate six times greater than the baseline scenario and four times the use of hydropower than that used in the baseline scenario. Greater carbon reductions (CM2; i.e., a 27% reduction) could be achieved with similar measures to CM1 but with more intensive penetration. Final energy demand would need to be cut by 13%, deployment of geothermal power plants would need to be seven times greater than at baseline, and hydropower use would need to be five times greater than the baseline case. Carbon prices under CM1

We developed a global land-use allocation model that can be linked to integrated assessment models (IAMs) with a coarser spatial resolution. Using the model, we performed a downscaling of the IAMs' regional aggregated land-use projections to obtain a spatial land-use distribution, which could subsequently be used by Earth system models for global environmental assessments of ecosystem services, food security, and climate policies. Here we describe the land-use allocation model, discuss the verification of the downscaling technique, and explain the influences of the downscaling on estimates of land-use carbon emissions. A comparison of the emissions estimated with and without downscaling suggested that the land-use downscaling would help capture the spatial distribution of carbon stock density and regional heterogeneity of carbon emissions caused by cropland and pasture land expansion.

The Paris Agreement confirmed the global aim to achieve a long-term climate goal, in which the global increase in mean temperature is kept below 2 °C compared to the preindustrial level. We investigated the implications of the near-term emissions targets (for around the year 2030) in the context of the long-term climate mitigation goal using the Asia-Pacific Integrated Model (AIM) framework. To achieve the 2 °C goal, a large greenhouse gas (GHG) emissions reduction is required, either in the early or latter half of this century. In the midterm (from 2030 to 2050), it may be necessary to consider rapid changes to the existing energy or socioeconomic systems, while long-term measures (after 2050) will rely on the substantial use of biomass combined with carbon capture and storage (CCS) technology or afforestation, which will eventually realize so-called negative CO2 emissions. With respect to the policy context, two suggestions are provided here. The first is the review and revision of the nationally determined contributions (NDCs) in 2020, with an additional reduction target to the current NDCs being one workable alternative. The second suggestion is a concrete and numerical midterm emissions reduction target, for example, to be met by 2040 or 2050, which could also help to achieve the long-term climate goal.

The objectives of the Paris Agreement (PA) include limiting the increase in the global average temperature to well below 2 °C (“the 2 °C goal”) and pursuing efforts to limit the increase to 1.5 °C (“the 1.5 °C goal”). The purpose of this chapter is to provide an overview of the relevant scientific knowledge on the risks from climate change corresponding to different levels of mitigation efforts, including the two long-term goals in the PA, as well as the expected consequences of extending the Intended Nationally Determined Contributions (INDCs) without strengthening them. According to figures summarizing risks from climate change in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC-AR5), if the global temperature increase could be limited to below 1.5 °C above the preindustrial level, this would reduce the risks from climate change as evaluated from several perspectives. However, some of the risks (such as the effects on unique and threatened systems and the risks from extreme events) would still be considerable even at 1–2 °C above the preindustrial level. Even with a similar degree of climate change, the levels of risk could differ under different degrees of exposure and/or vulnerability. To increase the accuracy of assessments of global climate risks for different temperature increases, explicit consideration of future changes in exposure and vulnerability will be necessary. Internationally coordinated development of new socioeconomic scenarios (Shared Socioeconomic Pathways, SSPs) is expected to promote such studies for the next round of the IPCC report.

This book analyzes the roles of technologies and their prevalence in implementing intended nationally determined contributions (INDCs), estimates the economic impacts and co-benefits of INDCs, clarifies the gaps between the current INDCs and the long-term target of the Paris Agreement to stay well below 2 °C, and investigates measures to narrow these gaps. Analyses of the INDCs of six Asian countries with the Asia-Pacific Integrated Modeling/Computable General Equilibrium (AIM/CGE) model are introduced. The book is also intended to support climate policy analyses by introducing methodologies to analyze the economic impacts of climate policies using AIM/CGE. These analyses show the feasibility of INDCs, their implications for the long-term climate goal, and the challenges to increase the levels of ambition of INDCs.

On 1st October 2015, Thailand had submitted its Intended Nationally Determined Contributions (INDCs) and stated that by 2030 GHG emissions will be reduced by 20–25% when compared to the business-as-usual (BAU) scenario. The Paris Agreement was adopted on 12 December 2015 at the twenty-first session of the Conference of the Parties (COP21) to the United Nations Framework Convention on Climate Change (UNFCCC) held in Paris. In addition, Thailand provided signature at the United Nations in New York on 22 April 2016 and ratified the Paris Agreement on 21 September 2016. This paper assesses the impacts of GHG emission reduction targets in Thailand’s INDC by using the Asia-Pacific Integrated Model/Computable General Equilibrium (AIM/CGE). Four scenarios are established by the given GHG emission constraints and the renewable power generation target. Results show that, under the Power Development Plan in 2015, the INDC target is achievable. As a result, macroeconomic loss is low in low reduction target, but it will be high in the high reduction target. In addition, it needs more renewable energy push to realize stringent climate policy. Thus, the availability of land for deploying the renewable energy technologies such as solar, wind, and biomass needs to be evaluated to meet higher GHG emission levels. Furthermore, the stringent GHG emission levels also induce the reduction of other air pollutants. Finally, the result of this study has been used in the design of roadmap for GHG reduction targets in 2030, and Thailand has more confidence on the achievement of the Paris Agreement.

This chapter documents a main model structure and how to implement scenario assumptions for the analysis of long-term climate mitigation taken by AIM/CGE (Asia-Pacific Integrated Model/Computable General Equilibrium). There are six aspects which are going to be discussed. First, macroeconomy, labor, and population treatment are explained. Second, energy supply sector representation is described. Energy supply sectors are one of the key elements for decarbonizing economic systems. Third, energy demand sectors are discussed. Fourth, agriculture and land use are critically important for stringent climate mitigation policy since large bioenergy implementation combined with carbon capture and storage and afforestation would be thought as measures which enables so-called negative emissions. Fifth, nonenergy-related GHG reduction measures follow. They are mostly related to agricultural sectors. Sixth, we discuss how to add new sectors into the CGE system.

Each country’s Intended Nationally Determined Contribution (INDC) pledges an emission target for 2025 or 2030. Here, we evaluated the INDC intergenerational and interregional equity by comparing scenarios with INDC emission target in 2030 and with an immediate emission reduction associated with a global uniform carbon price using AIM/CGE (Asian-Pacific Integrated Model/Computable General Equilibrium). Both scenarios eventually achieve 2 °C target. The results showed that, as compared with an immediate emission reduction scenario, the intergenerational equity status is not favorable for INDC scenario and the future generation suffers more from delayed mitigation. Moreover, this conclusion was robust to the wide range of inequality aversion parameter that determines discount rate. On the other hand, the INDC scenario has better interregional equity in the early part of the century than does the immediate emission reduction scenario in which we assume a global carbon price during the period up to 2030. However, interregional equity worsens later in the century. The additional emission reduction to the INDC in 2030 would improve both inter- and interregional equity as compared to the current INDC. We also suggest that countries should commit to more emission reductions in the follow-up INDC communications and that continuous consideration for low-income countries is needed for global climate change cooperation after 2030.

Under the Paris Agreement, parties would set and implement their own emissions targets as nationally determined contributions (NDCs) to tackle climate change risk. The international carbon emissions trading (ET) is expected to reduce global mitigation costs. Here we show the benefit of ET under both NDCs. The results show that the global welfare loss, which was measured based on estimated household consumption change in 2030, decreased by 80% (from 0.5 to 0.1%), as a consequence of achieving the NDCs through ET. These results indicate that ET is a valuable option for the international system, enabling the NDCs to be cost-effectively achieved and more ambitious targets.

This book summarizes assessments of the Paris Agreement to provide an excellent introduction to this research field. The AIM/CGE (Asia-Pacific Integrated Modeling /Computable General Equilibrium) model, which is the core of AIM modeling framework, is used for the assessment. The first part focuses on global issues, presenting both short-term (a few decades) and long-term (century scale) assessments in the context of the Agreement’s ultimate climate goal. It also discusses policy implementation and climate risk. Part 2 is a collection of assessments of individual Asian countries, providing insights into the national situations and detailed analyses. It includes contributions from Asian countries as well as NIES (National Institute for Environmental Studies, Japan) members. The main conclusion is that many countries require changes to their energy systems change and societal transformation in order to meet emissions targets. Part 3 describes in detail the AIM/CGE model, which is used to evaluate the climate and energy policies by simulating the future economic and energy and environmental situation in the Asia-Pacific region. This section can be used as a standard text on CGE modelling in climate change mitigation.

This chapter describes the (1) model structure of AIM/CGE (Asia-Pacific Integrated Model/Computable General Equilibrium), (2) data structure (social accounting matrix (SAM)), and (3) formula and list of sets, parameters, equations, and variables. The aim of this chapter is to present all equations written in the model which is used in the other chapter’s analysis and make the analysis made in this book transparent.

This chapter provides an overview of Indonesia’s current economy, energy sector, land use, and climate policies. We assessed Indonesia’s Intended Nationally Determined Contributions (INDC) using an Asia-Pacific Integrated Model/Computable General Equilibrium model coupled with an agriculture, forestry, and other land use (AFOLU) model. The model shows that the emission reduction target of INDC can be achieved at low economic cost (less than 1% of GDP) and that the mitigation actions required would not harm economic development. While emissions from land use and land use change are high nowadays, the energy sector is expected to grow rapidly and become more important in the future. Therefore, climate-related policymakers should focus equally on land use and the energy sector in the future.

This paper presents the overview of the Shared Socioeconomic Pathways (SSPs) and their energy, land use, and emissions implications. The SSPs are part of a new scenario framework, established by the climate change research community in order to facilitate the integrated analysis of future climate impacts, vulnerabilities, adaptation, and mitigation. The pathways were developed over the last years as a joint community effort and describe plausible major global developments that together would lead in the future to different challenges for mitigation and adaptation to climate change. The SSPs are based on five narratives describing alternative socio-economic developments, including sustainable development, regional rivalry, inequality, fossil-fueled development, and a middle-of-the-road development. The long-term demographic and economic projections of the SSPs depict a wide uncertainty range consistent with the scenario literature. A multi-model approach was used for the elaboration of the energy, land-use and the emissions trajectories of SSP-based scenarios. The baseline scenarios lead to global energy consumption of 500-1100 EJ in 2100, and feature vastly different land-use dynamics, ranging from a possible reduction in cropland area up to a massive expansion by more than 700 million hectares by 2100. The associated annual CO2 emissions of the baseline scenarios range from about 25 GtCO2 to more than 120 GtCO2 per year by 2100. With respect to mitigation, we find that associated costs strongly depend on three factors: 1) the policy assumptions, 2) the socio-economic narrative, and 3) the stringency of the target. The carbon price for reaching the target of 2.6 W/m2 differs in our analysis thus by about a factor of three across the SSP scenarios. Moreover, many models could not reach this target from the SSPs with high mitigation challenges. While the SSPs were designed to represent different mitigation and adaptation challenges, the resulting narratives and quanti

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 21st 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.

Under the Paris Agreement, parties set and implement their own emissions targets as nationally determined contributions (NDCs) to tackle climate change. International carbon emissions trading is expected to reduce global mitigation costs. Here, we show the benefit of emissions trading under both NDCs and a more ambitious reduction scenario consistent with the 2 °C goal. The results show that the global welfare loss, which was measured based on estimated household consumption change in 2030, decreased by 75% (from 0.47% to 0.16%), as a consequence of achieving NDCs through emissions trading. Furthermore, achieving the 2 °C targets without emissions trading led to a global welfare loss of 1.4%–3.4%, depending on the burden-sharing scheme used, whereas emissions trading reduced the loss to around 1.5% (from 1.4% to 1.7%). These results indicate that emissions trading is a valuable option for the international system, enabling NDCs and more ambitious targets to be achieved in a cost-effective manner.

We investigated the key mitigation options for achieving the mid-term target for carbon emission reduction in Indonesia. A computable general equilibrium model coupled with a land-based mitigation technology model was used to evaluate specific mitigation options within the whole economic framework. The results revealed three primary findings: (1) If no climate policy were implemented, Indonesia’s total greenhouse gas emissions would reach 3.0 GtCO2eq by 2030; (2) To reduce carbon emissions to meet the latest Intended Nationally-Determined Contributions (INDC) target, ~58% of total reductions should come from the agriculture, forestry and other land use sectors by implementing forest protection, afforestation and plantation efforts; (3) A higher carbon price in 2020 suggests that meeting the 2020 target would be economically challenging, whereas the INDC target for 2030 would be more economically realistic in Indonesia.

The Paris Agreement confirmed the global aim to achieve a long-term climate goal, in which the global increase in mean temperature is kept below 2 °C compared to the preindustrial level. We investigated the implications of the near-term emissions targets (for around the year 2030) in the context of the long-term climate mitigation goal using the Asia-Pacific Integrated Model framework. To achieve the 2 °C goal, a large greenhouse gas emissions reduction is required, either in the early or latter half of this century. In the mid-term (from 2030 to 2050), it may be necessary to consider rapid changes to the existing energy or socioeconomic systems, while long-term measures (after 2050) will rely on the substantial use of biomass combined with carbon capture and storage technology or afforestation, which will eventually realize so-called negative CO2 emissions. With respect to the policy context, two suggestions are provided here. The first is the review and revision of the nationally determined contributions (NDCs) in 2020, with an additional reduction target to the current NDCs being one workable alternative. The second suggestion is a concrete and numerical mid-term emissions reduction target, for example to be met by 2040 or 2050, which could also help to achieve the long-term climate goal.

Each country's Intended Nationally Determined Contribution (INDC) pledges an emission target for 2025 or 2030. Here, we evaluated the INDC inter-generational and inter-regional equity by comparing scenarios with INDC emissions target in 2030 and with an immediate emission reduction associated with a global uniform carbon price using Asian-Pacific Integrated Model/Computable General Equilibrium. Both scenarios eventually achieve 2 °C target. The results showed that, as compared with an immediate emission reduction scenario, the inter-generational equity status is not favorable for INDC scenario and the future generation suffers more from delayed mitigation. Moreover, this conclusion was robust to the wide range of inequality aversion parameter that determines discount rate. On the other hand, the INDC scenario has better inter-regional equity in the early part of the century than does the immediate emission reduction scenario in which we assume a global carbon price during the period up to 2030. However, inter-regional equity worsens later in the century. The additional emissions reduction to the INDC in 2030 would improve both inter- and inter-regional equity as compared to the current INDC. We also suggest that countries should commit to more emissions reductions in the follow-up INDC communications and that continuous consideration for low-income countries is needed for global climate change cooperation after 2030.