Probabilistic temperature change projections and energy system implications of greenhouse gas emission scenarios

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 °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.     

International climate regimes: Effects of delayed participation

This paper analyses how delayed participation by regions can affect international climate regimes in terms of the feasibility, costs, timing, magnitude and nature of the long-term mitigation response. We use the energy-systems optimization model MESSAGE to construct several climate change mitigation scenarios with various levels of regional participation in short-to-mid term. By comparing these with a global scenario that assumes full spatial and temporal flexibility throughout the century, we are able to evaluate how participatory decisions affect the mitigation response as well as the costs and technology choices. We find that short-term postponement of participation from some regions can often lead to a delay of mitigation measures on the global level. However, if the regional delay lasts until mid-century, participants of the regime are likely to increase their efforts in the short term. Mitigation costs are found to substantially increase as a result of delayed participation—the extent of the increase depends on the relative importance of the region that postpones its participation, the stringency of the climate target and the ability to reorganize mitigation measures. Our analysis also shows that a region's decision to delay its participation in an international climate regime can lead to accumulated inertia in its energy system and thus to a delayed ‘technological transition’ toward a low-carbon future.     

The opportunity cost of land use and the global potential for greenhouse gas mitigation in agriculture and forestry

This paper analyses the role of global land management alternatives in determining potential greenhouse gas mitigation by land-based activities in agriculture and forestry. Land-based activities are responsible for over a third of global greenhouse gas emissions, yet the economics of land-use decisions have not been explicitly modeled in global mitigation studies. In this paper, we develop a new, general equilibrium framework which effectively captures the opportunity costs of land-use decisions in agriculture and forestry, thereby allowing us to analyse competition for heterogeneous land types across and within sectors, as well as input substitution between land and other factors of production. When land-using sectors are confronted with a tax on greenhouse gas emissions, we find significant changes in the global pattern of comparative advantage across sectors, regions, and land types. Globally, we find that forest carbon sequestration is the dominant strategy for GHG emissions mitigation, while agricultural-related mitigation comes predominantly from reduced methane emissions in the ruminant livestock sector, followed by fertilizer and methane emissions from paddy rice. Regionally, agricultural mitigation is a larger share of total land-use emissions abatement in the USA and China, compared to the rest of the world, and, within agriculture, disproportionately from reductions in fertilizer-related emissions. The results also show how analyses that only consider regional mitigation, may bias mitigation potential by ignoring global market interactions. For example, USA-specific analyses likely over-estimate the potential for abatement in agriculture. Finally, we note that this general equilibrium framework provides the research community with a practical methodology for explicit modeling of global land competition and land-based mitigation in comprehensive assessments of greenhouse gas mitigation options.     

Reducing climate change impacts on agriculture: Global and regional effects of mitigation, 2000–2080

What are the implications for agriculture of mitigating greenhouse gas emissions? By when and by how much are impacts reduced? Where does it matter most? We investigated these questions within the new A2 emission scenario, recently developed at the International Institute of Applied Systems Analysis with revised population and gross domestic product projections. Coupling an agro-ecological model to a global food trade model, two distinct sets of climate simulations were analyzed: 1) A non-mitigated scenario, with atmospheric CO₂ concentrations over 800 ppm by 2100; and 2) A mitigation scenario, with CO₂ concentrations stabilized at 550 ppm by 2100. Impacts of climate change on crop yield were evaluated for the period 1990–2080, then used as input for economic analyses. Key trends were computed over the 21st century for food demand, production and trade, focusing on potential monetary (aggregate value added) and human (risk of hunger) impacts. The results from this study suggested that mitigation could positively impact agriculture. With mitigation, global costs of climate change, though relatively small in absolute amounts, were reduced by 75–100%; and the number of additional people at risk of malnutrition was reduced by 80–95%. Significant geographic and temporal differences were found. Regional effects often diverged from global net results, with some regions worse off under mitigation compared to the unmitigated case.     

气候变化对德国农业的影响与相关对策

本文分析和研究了气候变化对德国农业和林业的正反两方面的影响,肯定了德国农业和林业对气候保护、减少温室气体排放的积极作用。阐述了德国为减少温室气体排放采取的相应措施,如改进传统农业,扩大现代农业,大力生产可再生长原料,促进可再生能源的利用。这些做法对我国发展现代农业,促进农业和林业领域节能减排具有积极的参考作用。     

Timing of Mitigation and Technology Availability in Achieving a Low-Carbon World

This paper analyzes the economic and investment implications of a series of climate mitigation scenarios, characterized by different levels of ambition for long-term stabilization goals and transitional pathways. Results indicate that although milder climate objectives can be achieved at moderate costs, stringent stabilization paths, compatible with the 2°C target, might require significant economic resources. Innovation and technology are shown to be able to mitigate, but not structurally alter, this trade-off. Technologies that allow capturing CO₂ from the atmosphere are shown to be important for expanding the feasibility space of stringent climate policies, though only if deployed at a scale which would represent a tremendous challenge. In general, the analysis indicates that the timing of mitigation is an important factor of cost containment, with early action being desirable. It also elaborates on the set of mitigation strategies and policies that would be required to achieve climate protection at maximum efficiency.     

Transition of the Chinese Economy in the Face of Deep Greenhouse Gas Emissions Cuts in the Future

China joined the Paris Agreement, and the global 2°C and 1.5°C warming targets will be supported by China. In order to achieve these targets, China's CO₂ emissions need to be cut deeply by 2050. The present paper presents studies from the integrated policy assessment model for China (IPAC) team about the impact on China's economic development of deep cuts in greenhouse gas (GHG) emissions, in order to realize the Paris climate change targets. With the requirement of deep cuts in GHG emissions in China, China's economic development will also be impacted in moving toward a low‐carbon or zero‐carbon emission‐based economy by 2050. This means the Chinese economy needs a strong transition over the next three decades, a relatively short time. All sectors in the economy need to seek ways to reduce GHG emissions, and this could change activities, industry processes and technologies in order to make the deep cuts in GHG emissions happen. This is the meaning of the economic transition toward to a low‐carbon economy. The findings of the present paper include: a significant transition in the energy supply sector; a high rate of electrification in all end‐use sectors; and a technology transition in the transport sector. Transitions will also occur in the traditional industrial sectors, including steel making, cement manufacture, and the chemical sector. The availability of low‐cost renewable energy could change the allocation of industries, which could potentially have a strong impact on regional economic development. Deep cuts in CO₂ emissions in China need not be a burden for economic development, as the IPAC results show there will be a more than 1.5% increase of gross domestic product by 2050 in the deep cut scenario compared with the baseline scenario.     

Policy Framework for Transition to a Low-Carbon World Economy

Climate change mitigation policy is the most difficult to come before our polity in living memory. There can be no solution without international agreement involving all substantial economies, and yet each country has an incentive to free ride on others. The international agreement must have five parts: agreement on the objective in terms of concentrations of greenhouse gases in the atmosphere, agreement on allocation of an emissions entitlements budget among countries, agreement on rules for international trade in entitlements, agreement on developed countries taking the lead on development of low-emissions technologies, and agreement on assistance from developed countries for climate change mitigation in developing countries. Two sources of market failure must be corrected to achieve emissions reduction targets efficiently: the external costs of emitting greenhouse gases and the external benefits of private investment in innovation in relation to low-emissions technologies.     

Taxation of multiple greenhouse gases and the effects on income distribution: A case study of the Netherlands

Current economic instruments aimed at climate change mitigation focus on CO₂ emissions only, but the Kyoto Protocol refers to other greenhouse gases (GHG) as well as CO₂. These are CH₄, N₂O, HFCs, PFCs and SF₆. Taxation of multiple greenhouse gases improves the cost-effectiveness of climate change mitigation. It is not yet clear, however, what the effect is of multigas taxation on the distribution of the tax burden across income groups. This paper examines and compares distributional effects of a CO₂ tax and a comprehensive tax that covers all six GHG of the Kyoto Protocol. The study concentrates on the Netherlands in the year 2000. We established tax rates on the basis of marginal abatement cost curves and the Dutch policy target. The distributional effects have been determined by means of environmentally extended input−output analysis and data on consumer expenditures. Our results show that taxation of multiple GHG improves not only the cost-effectiveness of climate change mitigation, but also distributes the tax burden more equally across income groups as compared to a CO₂ tax. These findings are relevant for the debate on the role of non-CO₂ GHG in climate change mitigation.     

Spatial organization, transport, and climate change: Comparing instruments of spatial planning and policy

Approaching the analysis of climate policies from a spatial organization perspective is necessary for realizing both efficient and effective mitigation of greenhouse gas (GHG) emissions. In particular, it allows assessing the potential contribution of specific mechanisms of spatial organization and related spatial planning and policy to climate policy goals. So far, this spatial organization angle of climate policy has hardly received attention in the literature. The main sector significantly contributing to GHG emissions and sensitive to spatial organization and planning is urban transport. A qualitative evaluation of the available spatial organization policy options is provided, on the basis of four standard ‘E criteria’ and a decomposition of CO₂ emissions.     

Spatial organization,transport, and climate change: Comparing instruments of spatial planning and policy

Approaching the analysis of climate policies from a spatial organization perspective is necessary for realizing both efficient and effective mitigation of greenhouse gas (GHG) emissions. In particular, it allows assessing the potential contribution of specific mechanisms of spatial organization and related spatial planning and policy to climate policy goals. So far, this spatial organization angle of climate policy has hardly received attention in the literature. The main sector significantly contributing to GHG emissions and sensitive to spatial organization and planning is urban transport. A qualitative evaluation of the available spatial organization policy options is provided, on the basis of four standard ‘E criteria’ and a decomposition of CO₂ emissions.     

Climate change impacts on irrigation water requirements: Effects of mitigation, 1990–2080

Potential changes in global and regional agricultural water demand for irrigation were investigated within a new socio-economic scenario, A2r, developed at the International Institute for Applied Systems Analysis (IIASA) with and without climate change, with and without mitigation of greenhouse gas emissions. Water deficits of crops were developed with the Food and Agriculture Organization (FAO)–IIASA Agro-ecological Zone model, based on daily water balances at 0.5° latitude × 0.5° longitude and then aggregated to regions and the globe. Future regional and global irrigation water requirements were computed as a function of both projected irrigated land and climate change and simulations were performed from 1990 to 2080. Future trends for extents of irrigated land, irrigation water use, and withdrawals were computed, with specific attention given to the implications of climate change mitigation. Renewable water-resource availability was estimated under current and future climate conditions. Results suggest that mitigation of climate change may have significant positive effects compared with unmitigated climate change. Specifically, mitigation reduced the impacts of climate change on agricultural water requirements by about 40%, or 125–160 billion m³ (Gm³) compared with unmitigated climate. Simple estimates of future changes in irrigation efficiency and water costs suggest that by 2080 mitigation may translate into annual cost reductions of about 10 billion US$.     

Beyond Kyoto, plan B: A climate policy master plan based on transparent metrics

Many scholars analyze the Kyoto–Copenhagen process, and offer corrective suggestions for identified flaws in the present design. Based on various proposals in the literature, this article adopts a global master-plan perspective, leaving executive architecture to sovereign participants. Transparent, flexible and fair top-down rules must synchronize the numerous bottom-up initiatives while addressing the diversity of national circumstances in the drastic transformation of the world's energy economies.Plan B refutes absolute emission reduction targets on old or speculative baselines. It criticizes global tax and permit trade instruments for being ineffective, inefficient and unfair when uniformly applied on a tremendous differentiated world. Plan B is built on three annually observed variables measuring percentage progress against rolling baselines (the variables' values in the previous year): the ratio of net climate tax revenues to GDP, the commercial energy intensity of GDP, and the carbon intensity of commercial energy use. The three variables together indicate countries' progress affecting emissions per person, a metric that must converge to lower bands when climate change is addressed seriously. Long-term scenarios of global convergence “funnels” serve as guidance to frame near-term actions rich and poor countries individually propose to take. The global regime is common for all countries, and is ranked by GDP per person to determine whether a nation is a donor or a beneficiary in a Global Climate Transfer Fund. Fund payments and drawing rights depend on that ranking but also on the performances of the countries in realizing committed progress. The transparent mechanisms of the design and of the fund persuasively invite countries to participate in a fair, self-enforcing agreement.     

Taxation of multiple greenhouse gases and the effects on income distribution: A case study of the Netherlands

Current economic instruments aimed at climate change mitigation focus on CO₂ emissions only, but the Kyoto Protocol refers to other greenhouse gases (GHG) as well as CO₂. These are CH₄, N₂O, HFCs, PFCs and SF₆. Taxation of multiple greenhouse gases improves the cost-effectiveness of climate change mitigation. It is not yet clear, however, what the effect is of multigas taxation on the distribution of the tax burden across income groups. This paper examines and compares distributional effects of a CO₂ tax and a comprehensive tax that covers all six GHG of the Kyoto Protocol. The study concentrates on the Netherlands in the year 2000. We established tax rates on the basis of marginal abatement cost curves and the Dutch policy target. The distributional effects have been determined by means of environmentally extended input−output analysis and data on consumer expenditures. Our results show that taxation of multiple GHG improves not only the cost-effectiveness of climate change mitigation, but also distributes the tax burden more equally across income groups as compared to a CO₂ tax. These findings are relevant for the debate on the role of non-CO₂ GHG in climate change mitigation.     

Climate change and the transition to a low carbon economy – Carbon targets and the carbon budget

Carbon intensive fuels generate a significant negative externality which is quite relevant for climate change mitigation policy. We propose a dynamic growth model where output is produced using two types of energy sources: fossil fuel and renewable energy. Fossil fuel discovery, extraction, and associated costs are incorporated in our model together with the dynamics of greenhouse gas emissions and consequent damages. Consistent with the empirical facts, our numerical solutions suggest that fossil fuels, especially coal, should not be exploited to depletion. Furthermore, renewable energy should be gradually phased in to meet targets consistent with the Paris 2015 agreement. We show that adopting those policies should slow down the growth rate of cumulative emissions; but the outcome is contingent upon the carbon emission targets set for advanced countries, as distinct from those assigned to developing countries.     

Renewable energy subsidies: Second-best policy or fatal aberration for mitigation?

This paper evaluates the consequences of renewable energy policies on welfare and energy prices in a world where carbon pricing is imperfect and the regulator seeks to limit emissions to a (cumulative) target. The imperfectness of the carbon price is motivated by political concerns regarding distributional effects of increased energy prices. Hence, carbon prices are considered to be temporarily or permanently absent or endogenously constrained by their effect on energy prices. We use a global general equilibrium model with an intertemporal fossil resource sector and calculate intertemporally optimal policies from a broad set of policy instruments including carbon taxes, renewable energy subsidies and feed-in-tariffs, among others. If carbon pricing is permanently missing, mitigation costs increase by a multiple (compared to the optimal carbon pricing policy) for a wide range of parameters describing extraction costs, renewable energy costs, substitution possibilities and normative attitudes. Furthermore, we show that small deviations from the second-best subsidy can lead to strong increases in emissions and consumption losses. This confirms the rising concerns about the occurrence of unintended side effects of climate policy – a new version of the green paradox. Smart combinations of carbon prices and renewable energy subsidies, however, can achieve ambitious mitigation targets at moderate additional costs without leading to high energy price increases.     

气候变化政策中的技术变迁模型

技术变迁对于减缓和适应气候变化起着至关重要的作用。对近年来关于气候变化政策模型研究中的技术变迁处理方法进行了回顾。气候变化政策模型中广泛应用的有"自下而上"和"自上而下"两种方法,前者强调对能源系统细节的、技术性的处理方法,后者强调理论上对整个经济体的一致性描述。自下而上和自上而下模型都是为了帮助设计温室气体的减排政策,但是两种模型都依赖于对能源替代性和技术变迁动力学的过于简单的假设。通过对气候变化政策分析中常用的综合性模型进行归纳,总结不同模型的前提假设和模型中处理技术变迁的不同方法,以及不同的计算方法。     

Capital Malleability, Emission Leakage and the Cost of Partial Climate Policies: General Equilibrium Analysis of the European Union Emission Trading System

Computable general equilibrium (CGE) models are the premier analytical platform for assessing the economic impacts of climate change mitigation. But these models tend to treat physical capital as “malleable”, capable of reallocation among sectors over the time-period for which equilibrium is solved. Because the extent to which capital adjustment costs might dampen reallocation is not well understood, there is concern that CGE assessments understate the true costs of greenhouse gas (GHG) reduction policies. This paper uses a multi-region, multi-sector CGE model to investigate cap-and-trade schemes, such as the European Union Emission Trading System which cover a subset of the economy, elucidating the effects of capital malleability on GHG abatement, the potential for emission leakage from abating to non-abating sectors, and the impacts on welfare. To simplify the complex interactions being simulated within the CGE model, that analysis is complemented with an analytical model. A partial climate policy results in negative internal carbon leakage, with emissions declining not only in capped sectors but also in non-regulated ones. This result is stronger when capital is intersectorally mobile. Interestingly, in partial climate policy settings capital malleability can amplify or attenuate welfare losses depending on the attributes of the economy.     

From production-based to consumption-based national emission inventories

Under the United National Framework Convention of Climate Change (UNFCCC) countries are required to submit National Emission Inventories (NEI) to benchmark reductions in greenhouse gas (GHG) emissions. Depending on the definition and system boundary of the NEI, the mitigation options and priorities may vary. The territorial system boundary used by the UNFCCC has been critiqued for not including international transportation and potentially causing carbon leakage. To address these issues, past literature has argued in favour of using consumption-based NEI in climate policy. This article discusses several issues in moving from the standard production-based NEI to consumption-based NEI. First, two distinct accounting approaches for constructing consumption-based NEI are presented. The approaches differ in the allocation of intermediate consumption of imported products. Second, a consistent method of weighting production-based and consumption-based NEI is discussed. This is an extension of the previous literature on shared responsibility to NEI. Third, due to increased uncertainty and a wide system boundary it may be difficult to implement consumption-based NEI directly into climate policy. Several alternative options for incorporating consumption-based inventories into climate policy are discussed.     

Long-Run Implications for Developing Countries of Joint Implementation of Greenhouse Gas Mitigation

Joint Implementation (JI) calls for cooperation between industrialized and developing countries in the mitigation of greenhouse gas (GHG) emissions. However, a major concern of potential host countries is that, if they utilize their low-cost options for JI now, they will be left with only high cost options in the future, thereby penalizing them at a time when they may be obligated to mitigate GHGs themselves. This paper formalizes this hypothesis by utilizing an optimal control framework analogous to the Hotelling model of non-renewable resource extraction. The results are that cumulative abatement effects can impose costs on the future, but that they can be offset by technological change, market power, or compensation.