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The framework presented in this study aims to provide insights into how climate policy is represented in integrated assessment models, responding to the call to link model scenarios with concepts used in public policy literature and related fields. As such, it contributes to increased transparency leading to better understanding across disciplines and communication about the relevance of model outcomes with policymakers. The framework categorises climate policy into policy aims and policy implementation at different stages of the policy cycle, and can be used to demarcate different climate policy scenarios incorporating and linking the international and national level. This approach provides clarity on critical modelling assumptions concerning the workings of policy to scenario users (including policymakers), such as policy stringency and status. We discuss the framework in relation to scenarios exploring pathways meeting the long-term Paris goal to hold temperature well below 2 °C or 1.5 °C, Nationally Determined Contributions submitted to the Paris Agreement, and current implemented policies. Specifically, the application of the framework and model implementation of the scenarios is illustrated with implementation in the IMAGE model. To project the expected policy impact on greenhouse gas emissions, the policy goals and policy instrument targets are translated into model targets. This is implemented in the model by either changing parameters for available policy instruments, such as carbon price or subsidies, or adjusting model parameters such as efficiency and costs to meet targets. • We developed a climate policy framework that integrates models and policy design. • The framework helps modellers, scholars and policymakers speak the same language. • This framework can be used to make policy representation in models more transparent. • Models represent policy instruments by replicating the impact on emissions. [ABSTRACT FROM AUTHOR]

• Assesses if nine key non-G20 countries meet 2030 GHG targets with existing policies. • Only Colombia, Iran, Morocco and Ukraine will likely meet their targets. • Thailand and DRC within reach; Kazakhstan and Philippines will miss their targets. • Per capita emissions under existing policies increase by 8 % to over 40 %. • Need to strengthen climate action analysis outside G20 for Paris Agreement goals. This study compares greenhouse gas (GHG) emissions projections in 2030 under current policies and those under 2030 mitigation targets for nine key non-G20 countries, that collectively account for about 5 % of global total emissions today. These include the four largest non-G20 fossil CO 2 emitting Parties to the UN climate convention pre- Paris Agreement (Iran, Kazakhstan, Thailand and Ukraine) and one of the largest land-use GHG emitters in the world (Democratic Republic of the Congo). Other countries assessed include major economies in their respective regions (Chile, Colombia, Morocco and the Philippines). In addition to economy-wide GHG emissions projections, we also assessed the projected GHG emissions peak year and the progression of per capita GHG emissions up to 2030. Our GHG emissions projections are also compared with previous studies. On economy-wide GHG emissions, Colombia, Iran, Morocco, and Ukraine were projected to likely meet or significantly overachieve their unconditional 2030 targets with existing policies, while DRC and Thailand would come very close to their targets. Kazakhstan and the Philippines would need to strengthen their action to meet their targets, while Chile recently raised its 2030 target ambition. Only Colombia and Ukraine are projected to have peaked their emissions by 2030. Per capita GHG emissions excluding land-use under current policies were projected to increase in all countries from 2010 levels by 8 % to over 40 % depending on the country. While the impact of the COVID-19 crisis on 2030 emissions is highly uncertain, our assessment on the target achievement would not change for most countries when the emission reductions estimated for 2020 in the literature were assumed to remain in 2030. The findings of this study highlight the importance of enhanced and frequent progress-tracking of climate action of major emitters outside G20, as is currently done for G20 members, to ensure that the global collective progress will become aligned with the pathways toward Paris climate goals. [ABSTRACT FROM AUTHOR]

As part of the Paris climate agreement, countries have submitted (Intended) Nationally Determined Contributions (NDCs), which includes greenhouse gas reduction proposals beyond 2020. In this paper, we apply the IMAGE integrated assessment model to estimate the annual abatement costs of achieving the NDC reduction targets, and the additional costs if countries would take targets in line with keeping global warming well below 2 °C and “pursue efforts” towards 1.5 °C. We have found that abatement costs are very sensitive to socio-economic assumptions: under Shared Socioeconomic Pathway 3 (SSP3) assumptions of slow economic growth, rapidly growing population, and high inequality, global abatement costs of achieving the unconditional NDCs are estimated at USD135 billion by 2030, which is more than twice the level as under the more sustainable socio-economic assumptions of SSP1. Furthermore, we project that the additional costs of full implementation of the conditional NDCs are substantial, ranging from 40 to 55 billion USD, depending on socio-economic assumptions. Of the ten major emitting economies, Brazil, Canada and the USA are projected to have the highest cots as share of GDP to implement the conditional NDCs, while the costs for Japan, China, Russia, and India are relatively low. Allowing for emission trading could decrease global costs substantially, by more than half for the unconditional NDCs and almost by half for the conditional NDCs. Finally, the required effort in terms of abatement costs of achieving 2030 emission levels consistent with 2 °C pathways would be at least three times higher than the costs of achieving the conditional NDCs – even though reductions need to be twice as much. For 1.5 °C, the costs would be 5–6 times as high. [ABSTRACT FROM AUTHOR]

Greenhouse gas emissions associated with Representative Concentration Pathway RCP2.6 could limit global warming to around or below a 2 °C increase since pre-industrial times. However this scenario implies very large and rapid reductions in both carbon dioxide (CO 2 ) and non-CO 2 emissions, and suggests a need to understand available flexibility between how different greenhouse gases might be abated. There is a growing interest in developing a greater understanding of the particular role of shorter lived non-CO 2 gases as abatement options. We address this here through a sensitivity study of different methane (CH 4 ) emissions pathways to year 2100 and beyond, by including exchanges with CO 2 emissions, and with a focus on related climate and economic advantages and disadvantages. Metrics exist that characterise gas equivalence in terms of climate change effect per tonne emitted. We analyse the implications of CO 2 and CH 4 emission exchanges under two commonly considered metrics: the 100-yr Global Warming Potential (GWP-100) and Global Temperature Potential (GTP-100). This is whilst keeping CO 2 -equivalent emissions pathways fixed, based on the standard set of emissions usually associated with RCP2.6. An idealised situation of anthropogenic CH 4 emissions being reduced to zero across a period of two decades and with the implementation of such cuts starting almost immediately gives lower warming than for standard RCP2.6 emissions during the 21st and 22nd Century. This is despite exchanging for higher CO 2 emissions. Introducing Marginal Abatement Cost (MAC) curves provides an economic assessment of alternative gas reduction strategies. Whilst simpler than utilising full Integrated Assessment Models (IAMs), MAC curves are more transparent for illustrative modelling. The GWP-100 metric places a relatively high value on climate change prevented for methane emission reduction, as compared to an equivalent mass of CO 2 reduction. This in combination with the strong non-linearity in MAC curves (moving quickly from relatively cheap removal to emissions difficult to cut at any cost) causes little change under cost minimisation from standard RCP2.6 emissions. This reflects the original development of RCP2.6 standard emissions from similar minimisation. With gas exchange under GTP-100, however, we find much less methane is abated, resulting in higher temperatures, whilst costs are slightly lower. Our results also highlight the point at which greater methane mitigation would become beneficial from both a climate and economic aspect. If by 2030 removal of all methane were to become possible at an average cost less than $1000 per tonne of CH 4 , then this would be the cheapest option, for GWP-100 metric and our CO 2 MAC curve. Critically this would increase the possibility of constraining warming to two degrees. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the AMPERE modeling comparison project with focus on the implications of near-term policies for the costs and attainability of long-term climate objectives. Nine modeling teams participated in the project to explore the consequences of global emissions following the proposed policy stringency of the national pledges from the Copenhagen Accord and Cancún Agreements to 2030. Specific features compared to earlier assessments are the explicit consideration of near-term 2030 emission targets as well as the systematic sensitivity analysis for the availability and potential of mitigation technologies. Our estimates show that a 2030 mitigation effort comparable to the pledges would result in a further “lock-in” of the energy system into fossil fuels and thus impede the required energy transformation to reach low greenhouse-gas stabilization levels (450 ppm CO 2 e). Major implications include significant increases in mitigation costs, increased risk that low stabilization targets become unattainable, and reduced chances of staying below the proposed temperature change target of 2 °C in case of overshoot. With respect to technologies, we find that following the pledge pathways to 2030 would narrow policy choices, and increases the risks that some currently optional technologies, such as carbon capture and storage (CCS) or the large-scale deployment of bioenergy, will become “a must” by 2030. [ABSTRACT FROM AUTHOR]

Highlights: [•] This study compares 2020 emission levels from pledges to those consistent with 2°C. [•] For a likely chance of 2°C, we find an emission gap of 8.7–12.6GtCO2equiv. by 2020. [•] The pledges could achieve 24–54% of the mitigation effort consistent with 2°C. [•] The effect of accounting rules is lower than in the UNEP (2012) emission gap report. [•] An emission gap does not imply that the 2°C target is definitely out of reach. [ABSTRACT FROM AUTHOR]

Abstract: This study assesses four proposals to generate funds for international climate financing in developing countries according to three criteria: adequacy, predictability and equitability. The focus year is 2020, in which USD 100 billion should be available for climate financing according to the Copenhagen Accord. The four financing proposals assessed include auctioning emission allowances (Norwegian Proposal), a global carbon tax (Swiss Proposal), an emissions trading (IET) levy, and a tax on international aviation and shipping emissions (bunker fuel emissions tax). Adequacy and predictability are assessed by calculating the revenue of the financing proposals for three mitigation scenarios. Equitability is assessed by comparing the regional distribution of costs of the financing proposals to that of a common but differentiated responsibilities and respective capabilities approach, which can be regarded as an equitable approach. For the calculations, the integrated FAIR model is used. Based on the three criteria above, we conclude that the Swiss Proposal and the bunker fuel emissions tax are the most promising financing proposals of the four. An IET levy receives a low score for all three criteria. Importantly, a low price on the carbon market, resulting from a low mitigation ambition level (as under the current unconditional Copenhagen Accord pledges), would undermine generating funding for all financing proposals analysed here except for the Swiss Proposal. Combining such proposals would therefore not increase the predictability of funding. [Copyright &y& Elsevier]

Abstract: As part of the Copenhagen Accord, Annex I Parties (industrialised countries) and non-Annex I Parties (developing countries) have submitted reduction proposals (pledges) and mitigation actions to the UNFCCC secretariat. Our calculations show that if the current reduction offers of Annex I and non-Annex I countries are fully implemented, global greenhouse gas emissions could amount to 48.6–49.7 GtCO2eq by 2020. Recent literature suggests that the emission level should be between 42 and 46 GtCO2eq by 2020 to maintain a “medium” chance (50–66%) of meeting the 2°C target. The emission gap is therefore 2.6–7.7 GtCO2eq. We have identified a combined set of options, which could result in an additional 2.8 GtCO2eq emission reduction. This would lead to an emission level just within the range needed. The options include reducing deforestation and emissions from bunker fuels, excluding emissions allowance increases from land use and forestry rules, and taking into account the national climate plans of China and India. However, there are also important risks that could widen the emissions gap, like lower reductions from countries with only a conditional pledge and the use of Kyoto and/or trading of new surplus emission allowances. [Copyright &y& Elsevier]

Abstract: As part of the Copenhagen Accord, individual countries have submitted greenhouse gas reduction proposals for the year 2020. This paper analyses the implications for emission reductions, the carbon price, and abatement costs of these submissions. The submissions of the Annex I (industrialised) countries are estimated to lead to a total reduction target of 12–18% below 1990 levels. The submissions of the seven major emerging economies are estimated to lead to an 11–14% reduction below baseline emissions, depending on international (financial) support. Global abatement costs in 2020 are estimated at about USD 60–100 billion, assuming that at least two-thirds of Annex I emission reduction targets need to be achieved domestically. The largest share of these costs are incurred by Annex I countries, although the costs as share of GDP are similar for Annex I as a group and the seven emerging economies as a group, even when assuming substantial international transfers from Annex I countries to the emerging economies to finance their abatement costs. If the restriction of achieving two-thirds of the emission reduction target domestically is abandoned, it would more than double the international carbon price and at the same time reduce global abatement costs by almost 25%. [Copyright &y& Elsevier]

Abstract: Recent proposals at the UNFCCC meeting in Bali in December 2007 suggest that a 2% levy on the CDM could finance adaptation costs in developing regions. Other proposals include extending the scope of the levy to emissions trading. This study applies an Integrated Assessment Model to gain insight in the interactions between adaptation costs, residual damages and mitigation costs and to analyse the effectiveness of a 2% levy on both the CDM and emissions trading from developing countries. We show that adaptation is especially important in lower income regions where damages are higher. The revenues of a 2% levy strongly depend on both the climate mitigation target and the burden-sharing regime. A more stringent climate mitigation target results in more emissions trade and, in the longer run, less need for adaptation. Both factors increase the share of adaptation costs that can be funded. The burden-sharing regime strongly affects the revenues of a 2% levy as well: relatively more stringent targets for developed countries increase the revenues of a 2% levy. However, in the next two decades the share of adaptation that can be financed remains well below 20% in most cases. Additional funding mechanisms are therefore necessary to substantially finance adaptation costs in developing countries. [Copyright &y& Elsevier]

Abstract: The Stern Review on the Economics of Climate Change compares costs and benefits of stringent climate policy and concludes that the benefits of stringent policy considerably outweigh the costs. Many other cost–benefit analyses have come up with less ambitious optimal emission reductions. In this study, we systematically explore the impacts of scientific uncertainties and value judgements on the suggested “optimal target” for international climate policy. In this context, we have varied the most important parameters using a range of values from several widely used Integrated Assessment Modes in one consistent framework. Our analysis shows that uncertainties about abatement and damage costs play an almost equally important role as the discount rate. Both stringent and moderate climate policy can be justified by using other parameter settings. Furthermore, for most parameter settings there is a wide range of concentration levels close to the optimal target, providing a much wider range for political choices than often suggested. [Copyright &y& Elsevier]

This paper presents a set of technically feasible multi-gas emission pathways (envelopes) for stabilising greenhouse gas concentration at 450, 550 and 650ppm CO2-equivalent and their trade-offs between direct abatement costs and probabilities to meet temperature targets. There are different pathways within the envelope. Delayed response pathways initially follow the upper boundary of the emission envelope and reduce more by the end of the century. In contrast, early action pathways first follow the lower boundary and then the upper boundary. The latter require an early peak in the global emissions but keeps the option open for shifting to lower concentration targets in the future. Costs evaluations depend on the discount rate. Early action profiles have high costs early on, but learning-by-doing and smoother reduction rates over time lead to in most cases to lower costs across the century (net present value (NPV)). To achieve the 450ppm CO2-equivalent, the global emissions need to peak before 2020. The NPV of costs increase from 0.2% of cumulative gross domestic product to 1.0% as the shift is made from 650 to 450ppm (discount rate 5%). However, the chances of limiting global mean warming to 2°C above pre-industrial levels are very small for peaking and stabilisation at 650ppm (1–23%) and 550ppm (1–48%), but increase for a peaking at 510ppm with subsequent stabilisation 450ppm to 14–67%. [Copyright &y& Elsevier]

The “South–North Dialogue” Proposal, developed by researchers from developing and industrialised countries, outlined equitable approaches to mitigation. These approaches were based on the criteria of responsibility, capability and potential to mitigate, and include deep cuts in industrialised (Annex I) countries and differentiated mitigation commitments for developing countries. This paper quantitatively analyses the implications of the proposal for countries’ emissions and costs. The analysis focuses on a “political willingness” scenario and four stabilisation scenarios. The analysis shows that stringent stabilisation targets imply that many developing countries would have to take on quantitative mitigation obligations by 2030, even when the Annex I countries take on ambitious mitigation commitments far beyond the Kyoto obligations. The “political willingness scenario” will probably not suffice to limit a warming of the Earth''s atmosphere to below 2°C. [Copyright &y& Elsevier]

A methodology is presented here to assess the potential long-term contribution of non-CO2 greenhouse gases in mitigation scenarios. The analysis shows the future development of the mitigation potential of non-CO2 gases (as a function of changes in technology and implementation barriers) to represent a crucial parameter for the overall costs of mitigation scenarios. The recently developed marginal abatement cost curves for 2010 in the EMF-21 project are taken as the starting point. First-order estimates were made of the future maximum attainable reduction potentials and costs on the basis of available literature. The set of MAC curves developed was used in a multi-gas analysis for stabilising greenhouse gas concentrations at 550ppm CO2-equivalent. Including future development for the non-CO2 mitigation options not only increases their mitigation potential but also lowers the overall costs compared to situations where no development is assumed (3–21% lower in 2050 and 4–26% lower in 2100 in our analysis). Along with the fluorinated gases, energy-related methane emissions make up the largest share in total non-CO2 abatement potential as they represent a large emission source and have a large potential for reduction (towards 90% compared to baseline in 2100). Most methane and nitrous oxide emissions from landuse-related sources are less simple to abate, with an estimated abatement potential in 2100 of around 60% and 40%, respectively. [Copyright &y& Elsevier]

Abstract: This paper evaluates the influence of different policy-related and scientific choices on the calculated regional contributions to global climate change (the “Brazilian Proposal”). Policy-related choices include the time period of emissions, the mix of greenhouse gases and different indicators of climate change impacts. The scientific choices include historical emissions and model representations of the climate system. We generated and compared results of several simple climate models. We find that the relative contributions of different nations to global climate change—from emissions of greenhouse gases alone—are quite robust, despite the varying model complexity and differences in calculated absolute changes. For the default calculations, the average calculated contributions to the global mean surface temperature increase in 2000 are about 40% from OECD, 14% from Eastern Europe and Former Soviet Union, 24% from Asia and 22% from Africa and Latin America. Policy-related choices, such as time period of emissions, climate change indicator and gas mix generally have larger influence on the results than scientific choices. More specifically, choosing a later attribution start date (1990 instead of 1890) for historical emissions, decreases the contributions of regions that started emitting early, such as the OECD countries by 6 percentage points, whereas it increases the contribution of late emitters such as Asia by 8 percentage points. However, only including the fossil CO2 emissions instead of the emissions of all Kyoto gases (fossil and land use change), increases the OECD contributions by 21 percentage points and decreases the contribution of Asia by 14 percentage points. [Copyright &y& Elsevier]

This paper examines to what extent climate change policies will alter the effectiveness of agreed-upon or future policies to reduce regional air pollution in Europe and vice versa. And when is it cost-effective to combat regional air pollution with clean technology instead of add-on technology?For this exercise, several extensions were made to the energy model TIMER, to introduce add-on abatement technologies, specified in terms of costs and reduction potentials, in order to be able to calculate cost-effective emission reduction strategies for different scenarios and regions.The results show that add-on technologies to reduce regional air pollution remain necessary throughout the century. The costs to reach the NOx emission reduction targets in Europe are about three times as high as for SO2. Mitigation costs averaged over the century by add-on technologies can be reduced by climate measures by 50–70% for SO2 and around 50% for NOx. The costs of SO2 and NOx mitigation by add-on technology in a world without climate policy are comparable or in some periods even higher than the costs of an integrated mitigation of SO2, NOx and CO2 emissions if a reduction of specific costs by learning is, in contrast with energy technologies, not assumed for abatement technologies. So, the costs of SO2 and NOx add-on measures avoided by climate policies can outweigh the costs of these climate measures. The total annual costs are in the order of 1 or 2% of the present GDP, depending on the scenario. [Copyright &y& Elsevier]

The aim of this study was to develop consistent scenarios of emissions, climate change and regional air pollution to enable an integrated analysis of the linkage between climate change and regional air pollution in Europe. An integrated modeling framework was developed for this purpose. The framework integrates state-of-the-art models and concepts from the area of climate change and regional air pollution and was supplemented by new modules (e.g. modeling long-term NH3 emissions in Europe, modeling dispersion and transformation of air pollutants under climate change).Consistent climate and air pollution policies were derived, both driven by the desire to achieve certain environmental goals. According to an analysis of scenarios with various combinations of climate and regional air pollution policies the quantitatively most relevant interactions are the effect of climate change policies on the energy mix and the resulting air pollution emissions. In the long-term the global SO2 emissions are expected to decrease (again), accordingly their effect on climate will be minor. Tentatively it can be concluded that for regional air pollution the development of the air pollutant emissions is more important than the effect of climate change on the dispersion and chemical transformation of air pollutants. [Copyright &y& Elsevier]