Explore the vast range of titles available.

The Paris Agreement introduces long-term strategies as an instrument to inform progressively more ambitious emission reduction objectives, while holding development goals paramount in the context of national circumstances. In the lead up to the twenty-first Conference of the Parties, the Deep Decarbonization Pathways Project developed mid-century low-emission pathways for 16 countries, based on an innovative pathway design framework. In this Perspective, we describe this framework and show how it can support the development of sectorally and technologically detailed, policy-relevant and country-driven strategies consistent with the Paris Agreement climate goal. We also discuss how this framework can be used to engage stakeholder input and buy-in; design implementation policy packages; reveal necessary technological, financial and institutional enabling conditions; and support global stocktaking and increasing of ambition.The Deep Decarbonization Pathways Project develops a framework to design low-emission development pathways. This Perspective discusses the framework and how it can support the development of national strategies to meet climate targets, as well as help achieve stakeholder engagement.

Nationally Determined Contributions (NDCs), submitted by Parties to the United Nations Framework Convention on Climate Change before and after the 21st Conference of Parties, summarize domestic objectives for greenhouse gas (GHG) emissions reductions for the 2025-2030 time horizon. In the absence, for now, of detailed guidelines for the format of NDCs, ancillary data are needed to interpret some NDCs and project GHG emissions in 2030. Here, we provide an analysis of uncertainty sources and their impacts on 2030 global GHG emissions based on the sole and full achievement of the NDCs. We estimate that NDCs project into 56.8-66.5 Gt CO2eq yr−1 emissions in 2030 (90% confidence interval), which is higher than previous estimates, and with a larger uncertainty range. Despite these uncertainties, NDCs robustly shift GHG emissions towards emerging and developing countries and reduce international inequalities in per capita GHG emissions. Finally, we stress that current NDCs imply larger emissions reduction rates after 2030 than during the 2010-2030 period if long-term temperature goals are to be fulfilled. Our results highlight four requirements for the forthcoming 'climate regime': a clearer framework regarding future NDCs' design, an increasing participation of emerging and developing countries in the global mitigation effort, an ambitious update mechanism in order to avoid hardly feasible decarbonization rates after 2030 and an anticipation of steep decreases in global emissions after 2030.

In this report, the third in this Series on health and climate change, we assess the changes in particle air pollution emissions and consequent effects on health that are likely to result from greenhouse-gas mitigation measures in the electricity generation sector in the European Union (EU), China, and India. We model the effect in 2030 of policies that aim to reduce total carbon dioxide (CO 2) emissions by 50% by 2050 globally compared with the effect of emissions in 1990. We use three models: the POLES model, which identifies the distribution of production modes that give the desired CO 2 reductions and associated costs; the GAINS model, which estimates fine particulate matter with aerodynamic diameter 2·5 μm or less (PM 2·5) concentrations; and a model to estimate the effect of PM 2·5 on mortality on the basis of the WHO's Comparative Risk Assessment methods. Changes in modes of production of electricity to reduce CO 2 emissions would, in all regions, reduce PM 2·5 and deaths caused by it, with the greatest effect in India and the smallest in the EU. Health benefits greatly offset costs of greenhouse-gas mitigation, especially in India where pollution is high and costs of mitigation are low. Our estimates are approximations but suggest clear health gains (co-benefits) through decarbonising electricity production, and provide additional information about the extent of such gains.

This study gives a synthesis of a model comparison assessing the technological feasibility and economic consequences of achieving greenhouse gas concentration targets that are sufficiently low to keep the increase in global mean temperature below 2 degrees Celsius above pre-industrial levels. All five global energy-environment-economy models show that achieving low greenhouse gas concentration targets is technically feasible and economically viable. The ranking of the importance of individual technology options is robust across models. For the lowest stabilization target (400 ppm CO₂ eq), the use of bio-energy in combination with CCS plays a crucial role, and biomass potential dominates the cost of reaching this target. Without CCS or the considerable extension of renewables the 400 ppm CO₂ eq target is not achievable. Across the models, estimated aggregate costs up to 2100 are below 0.8% global GDP for 550 ppm CO₂ eq stabilization and below 2.5% for the 400 ppm CO₂ eq pathway.

Carbon pricing is considered by most economists as a central dimension to any climate policy. It is assumed to bring simple, transparent, and cost-effective means to change investment and consumption behaviors. The most straightforward method is carbon taxation, but its implementation is more complex. This study provides a comparative analysis of carbon taxation in three countries—Sweden, Canada, and France—aimed at drawing lessons for the future of carbon taxation. Comparing the experience of the three countries reveals that carbon taxes, once in place, do have the intended effect. In this sense, they work well. However, the analysis also reveals very different situations in terms of advances, difficulties, and results, which highlights the need to carefully consider the social and political conditions for the acceptance and effective implementation of such economic instruments. Against this background, the comparative analysis yields four main insights that deserve further research from economics and social scientists: the ability to combine pure economic instruments and other regulation or policies and measures; the management of lobbies and vested interests; the identification of a clear strategy for the recycling of the carbon revenues, whether earmarked or not; and finally, the importance of these three dimensions of carbon taxes in the new settings of zero net emission policies.

The paper presents a model-based approach describing the impacts of climate change on the European energy system. Existing analyses only estimate a limited range of climate impacts over a limited geographical area. Using the POLES model and the results from several climate models, the present paper quantifies the main impacts of climate change on the European energy sector, country by country, thus achieving progress in this direction. As far as energy demand is concerned, our main finding is that higher temperatures will mean that air-conditioning will consume more energy, reaching about 53 Mtoe by 2100 in a scenario with no strong emissions constraints (A1B). On the other hand, less energy will be consumed for heating buildings, falling by about 65 Mtoe per year. This represents a net decrease in energy consumption of about 12 Mtoe by 2100. On the supply side, more constrained and expensive operating conditions for electric power plants will result in lower electricity generation by thermal, nuclear and hydro-power plants, with a maximum decrease of about 200 TWh in 2070 in the A1B scenario and 150 TWh in 2060 and 2080 for a low emissions scenario (E1). These effects vary a great deal across Europe and remain very dependent on the uncertainties affecting the results of the various climate models. This overall uncertainty may inhibit effective decisions. However, the study offers insights not otherwise available without the full coverage of the energy system provided by POLES and climate features provided by climate models. The study identifies the main impacts of climate change in a strategic sector and provides an “order of magnitude” or “central trend” for these impacts, which might be useful in an adaptive policy of act, learn and then act again.

Emissions of gases and particles from the combustion of fossil fuels and biofuels in Africa are expected to increase significantly in the near future due to the rapid growth of African cities and megacities. There is currently no regional emissions inventory that provides estimates of anthropogenic combustion for the African continent. This work provides a quantification of the evolution of African combustion emissions from 2005 to 2030, using a bottom-up method. This inventory predicts very large increases in black carbon, organic carbon, CO, NOx, SO2 and non-methane hydrocarbon emissions if no emission regulations are implemented. This paper discusses the effectiveness of scenarios involving certain fuels, specific to Africa in each activity sector and each region (western, eastern, northern and southern Africa), to reduce the emissions. The estimated trends in African emissions are consistent with emissions provided by global inventories, but they display a larger range of values. African combustion emissions contributed significantly to global emissions in 2005. This contribution will increase more significantly by 2030: organic carbon emissions will for example make up 50% of the global emissions in 2030. Furthermore, we show that the magnitude of African anthropogenic emissions could be similar to African biomass burning emissions around 2030.

In this report, the third in this Series on health and climate change, we assess the changes in particle air pollution emissions and consequent effects on health that are likely to result from greenhouse-gas mitigation measures in the electricity generation sector in the European Union (EU), China, and India. We model the effect in 2030 of policies that aim to reduce total carbon dioxide (CO2) emissions by 50% by 2050 globally compared with the effect of emissions in 1990. We use three models: the POLES model, which identifies the distribution of production modes that give the desired CO2 reductions and associated costs; the GAINS model, which estimates fine particulate matter with aerodynamic diameter 2.5 µm or less (PM^sub 2.5^) concentrations; and a model to estimate the effect of PM^sub 2.5^ on mortality on the basis of the WHO's Comparative Risk Assessment methods. Changes in modes of production of electricity to reduce CO2 emissions would, in all regions, reduce PM^sub 2.5^ and deaths caused by it, with the greatest effect in India and the smallest in the EU. Health benefits greatly offset costs of greenhouse-gas mitigation, especially in India where pollution is high and costs of mitigation are low. Our estimates are approximations but suggest clear health gains (co-benefits) through decarbonising electricity production, and provide additional information about the extent of such gains. [PUBLICATION ABSTRACT]

In this paper we analyze research gaps and identify new directions of research in relation to a number of facets of the Paris Agreement, including the new 1.5 °C objective, the articulation between near-term and long-term mitigation pathways, negative emissions, verification, climate finance, non-Parties stakeholders, and adaptation.

In the wake of the Fukushima nuclear accident, countries like Germany and Japan have planned a phase-out of nuclear generation. Carbon capture and storage (CCS) technology has yet to become a commercially viable technology with little prospect of doing so without strong climate policy to spur development. The possibility of using renewable power generation from wind and solar as a non-emitting alternative to replace a nuclear phase-out or failure to deploy CCS technology is investigated using scenarios from EMF27 and the POLES model. A strong carbon price appears necessary to have significant penetration of renewables regardless of alternative generation technologies available, but especially if nuclear or CCS are absent from the energy supply system. The feasibility of replacing nuclear generation appears possible at realistic costs (evaluated as total abatement costs and final user prices to households); however for ambitious climate policies, such as a 450 ppm target, CCS could represent a critical technology that renewables will not be able to fully replace without unbearable economic costs.