[en] 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 8.7–12.6 GtCO₂equiv. 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: The Copenhagen Accord of 2009 refers to a 2 °C target and encouraged countries to submit emission reduction proposals and actions (pledges) for the year 2020, which many did. Several studies determined the effect of these pledges on the global emission level in 2020, and analysed the gap between this emission level and the level consistent with least-cost emission pathways for achieving the 2 °C target. These studies were summarised in the UNEP emission gap reports. Since the UNFCCC climate negotiations in Cancún, 2010, business-as-usual emission projections have been updated and some countries submitted new pledges or clarified existing pledges. Furthermore, new accounting rules for land use and the use of surplus units were agreed in Durban (2011) and Doha (2012). This paper shows that together, these developments have led to an increase in the emission level resulting from the pledges of about 4 GtCO₂equiv. compared to our assessment before Cancún, mainly due to increased business-as-usual projections. According to our projections, the pledges lead to an emission level of 52.7–56.5 GtCO₂equiv. by 2020, which implies an emission gap of 8.7–12.6 GtCO₂equiv. for a likely chance (greater than 66% likelihood) and from 6.7 to 10.6 GtCO₂equiv. for a medium chance (50–66% likelihood) of achieving 2 °C. This does not imply that achieving 2 °C is out of reach with the current pledges, but it will require higher reduction rates beyond 2020 and will depend more heavily on future technological developments

[en] A high probability of limiting temperature increase to 2 deg. C requires a radiative forcing below 3 W/m², around the end of this century, according to current knowledge. This paper identifies conditions under which achieving such low radiative forcing levels is feasible. Calculations here show that such targets could be achieved, based on technical and physical considerations, provided some key conditions are met. These key conditions include early participation by major sectors and regions in sufficiently stringent policy regimes, and a wide portfolio of mitigation options. Bio-energy and carbon capture and storage (CCS) play an important role in achieving low stabilisation targets. This would require optimistic assumptions with respect to the expansion of the area needed for food production, to allow space for bio-energy crops, and a significant increase in the efficiency of second-generation biofuels. The sensitivity analysis shows that if certain technologies are removed from the available portfolio, low targets - especially the 2.6 W/m² target - are no longer within reach.

[en] In this article we explore several scenarios that aim at meeting radiative forcing targets at 4.5, 3.7, 2.9 and 2.6 W/m² by 2100. These scenarios are run under the assumption of participation of all countries by 2012 in climate policy and under the assumption of a significant delay in the participation of Russia and non-Annex I countries (up to 2030 and 2050). The study finds the lowest radiative forcing categories to be feasible under full participation, certainly if overshoot of targets is allowed and when bio-energy and carbon-capture-and-storage is added to the mitigation portfolio. In cases with severe delay in participation, the lowest targets become infeasible. For less strict targets (e.g. 3.7 W/m²), delayed participation leads to considerable costs increases (up to 90% for the stabilisation case). As a next step, scenarios with less delay in participation need to be explored.

[en] So-far, most climate mitigation studies look at climate policy strategies in a so-called first-best world, i.e. using the least expensive emission reduction options in all world regions and sectors. To explore the impact of limited participation of countries, we have run a set of scenarios that explore the impact of introducing a carbon tax in OECD, the BRIC countries (Brazil Russia, India and China) and the rest of the world. The results show that carbon taxes can effectively reduce greenhouse gas emissions. However, if low greenhouse gas concentration levels are to be achieved, early participation (in some form) of large developing countries is important to increase reduction potential. It should be noted that global carbon taxes (without additional assumptions) lead to relatively high costs in low-income regions. Cap-and-trade regimes have more flexibility to create a comparable distribution of costs amongst countries.

[en] 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 550 ppm 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

[en] Highlights: • Annual abatement costs of achieving national climate plans (NDCs) are projected. • The costs are very sensitive to different socio-economic assumptions. • The costs of the conditional NDCs are projected at USD 97–191 billion by 2030. • There are large differences in costs of achieving NDCs between countries. • The costs of achieving 2 °C are 3–3.5 times the costs of achieving conditional NDCs. - Abstract: 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.

[en] 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%.

[en] This study provides a conceptual framework for exploring the bargaining space within international climate negotiations based on important economic, political and environmental considerations. Based on it, we analyse combinations of the proposed emission reduction ranges for Annex I countries as a group (25-40% below 1990 levels) and non-Annex I as a group (15-30% below baseline) by 2020 to limit global warming to 2 deg. C. We use results of the FAIR model with costs estimates based on two energy system models. We conclude that the range of targets that comply with a set of criteria for economic, political and environmental considerations is smaller than that by environmental considerations alone. More specifically, we find that according to our criteria, a 30% Annex I reduction target below 1990 levels, combined with a 20% non-Annex I reduction target below baseline emission levels (i.e. 20 to 30% above 2005 levels), is the only combination of targets fulfilling all our criteria for both energy system models. Otherwise, reaching the 2 deg. C target becomes less likely, technically infeasible, or non-Annex I abatement costs are likely to exceed those of Annex I, a result, which we consider less plausible from a political viewpoint in our conceptual framework. - Highlights: → We study ranges of reduction targets for Annex I and non-Annex I regions by 2020 currently discussed in international negotiations (25-40%; 15-30%). → Trade-offs between the targets occur in terms of environmental, economic and political criteria. → A set of simple criteria results in reductions around 30% and 20% for Annex I and non-Annex I, respectively. → The global abatement costs for such targets are around 0.45-0.65 %-GDP in 2020. → Several factors such as trading, abatement cost estimates, regional allocation and international financing influence the outcomes.

[en] In order to limit global mean temperature increase, long-term greenhouse gas emissions need to be reduced. This paper discusses the implications of greenhouse gas emission reductions for major Asian regions (China, India, Indonesia, South-East Asia, Japan and Korea) based on results from the IMAGE modelling framework. Energy use in regions and economic sectors is affected differently by ambitious climate policies. We find that the potential for emission reduction varies widely between regions. With respect to technology choices in the power sector, we find major application of CO₂ storage in Indonesia and India, whereas Korea and India apply more solar and wind. Projections for Japan include a (debatable) large share of nuclear power. China and, India, and South-East Asia, show a diverse technology choice in the power sector. For the industry sector, we find that the recent rapid growth in China limits the potential for emission reduction in the next decades, assuming that recently built coal-based industry facilities are in use for the next decades. For the residential sector, the model results show that fewer households switch from traditional fuels to modern fuels in GHG mitigation scenarios. With respect to co-benefits, we find lower imports of fossil energy in mitigation scenarios and a clear reduction of air pollutant emissions. - Highlights: ► The potential for emission reduction varies widely between regions. ► Some regions have attractive CO₂ storage capacity; others have low-cost solar/wind potential. ► The recent rapid growth of Chinese industry may limit emission reduction potential for decades. ► Fewer households switch from traditional fuels to modern fuels in mitigation scenarios. ► Mitigation scenarios show less fossil energy import and reduction of air pollutant emission.

[en] This paper analyses the impact of postponing global mitigation action on abatement costs and energy systems changes in China and India. It compares energy-system changes and mitigation costs from a global and two national energy-system models under two global emission pathways with medium likelihood of meeting the 2 °C target: a least-cost pathway and a pathway that postpones ambitious mitigation action, starting from the Copenhagen Accord pledges. Both pathways have similar 2010–2050 cumulative greenhouse gas emissions. The analysis shows that postponing mitigation action increases the lock-in in less energy efficient technologies and results in much higher cumulative mitigation costs. The models agree that carbon capture and storage (CCS) and nuclear energy are important mitigation technologies, while the shares of biofuels and other renewables vary largely over the models. Differences between India and China with respect to the timing of emission reductions and the choice of mitigation measures relate to differences in projections of rapid economic change, capital stock turnover and technological development. Furthermore, depending on the way it is implemented, climate policy could increase indoor air pollution, but it is likely to provide synergies for energy security. These relations should be taken into account when designing national climate policies. - highlights: • We analyze long-term impacts of the international pledges for China and India. • We compare a least-cost pathway with a pathway starting from the Copenhagen pledges. • Postponing mitigation action implies much higher cumulative mitigation costs. • Postponing increases fossil fuel dependence and requires deeper long-term reductions. • Countries differ mainly due to different periods of rapid economic change