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The overlap in sources of greenhouse gas and local air pollutant emissions creates scope for policy measures to limit global warming and improve air quality simultaneously. In a first step, we derive estimates for the air pollution mortality-related component of the social cost of atmospheric release for 6 pollutants and 56 regions in the world. Combining these estimates with emission inventory data highlights that sector contributions to greenhouse gas emissions and air pollution health impacts differ widely across regions. Next, simulations of future emission pathways consistent with the 2 °C and 1.5 °C targets illustrate that strengthening climate policy ambition raises the total value of air quality co-benefits despite lower marginal co-benefits per tonne of greenhouse gas emissions abated. Finally, we use results from a multi-model ensemble to quantify and compare the value of health-related ambient air quality co-benefits of climate policy across sectors and regions. On the global level, overall air quality co-benefits range from $8 to $40 per tonne of greenhouse gases abated in 2030, with median across models and scenarios of $18/tCO2e. These results mask strong differentiation across regions and sectors, with median co-benefits from mitigation in the residential and service sectors in India exceeding $500/tCO2e. By taking a sector- and region-specific perspective, the results presented here reveal promising channels to improve human health outcomes and to ratchet up greenhouse gas reduction efforts to bridge the gap between countries’ pledges and the global targets of the Paris Agreement.

Carbon pricing can steer energy choices towards low-carbon fuels and foster energy conservation efforts. Simultaneously, higher fossil fuel prices may exacerbate energy poverty. A just portfolio of climate policies therefore requires a balanced instrument mix to jointly combat climate change and energy poverty. We review recent policy developments in the EU aimed at addressing energy poverty and the social implications of the climate neutrality transition. We then operationalise an affordability-based definition of energy poverty and numerically illustrate that recent EU climate policy proposals risk raising the number of energy poor when not accompanied with complementary measures, while alternative climate policy designs could lift more than 1 million households out of energy poverty through income-targeted revenue recycling schemes. While these schemes have low informational requirements and appear sufficient to avoid exacerbating energy poverty, the findings suggest that more tailored interventions are needed. Finally, we discuss how insights from behavioural economics and energy justice can help shape optimal policy packages and processes.

The new submission round of Nationally Determined Contributions (NDCs) under the Paris Agreement presents a critical opportunity to enhance the credibility and feasibility of national decarbonisation pathways. By better aligning mid- and long-term targets, countries can reduce inconsistencies in emissions trajectories and strengthen the foundation for achieving long-term goals. Drawing on the experience of the European Union’s 2030 and 2040 intermediate emission targets, we highlight key considerations for setting milestones towards mid-century net-zero goals.

The goal of limiting global mean warming to well below 2 °C, and possibly to 1.5 °C, emerged in the Paris Agreement, motivated by the belief that achieving these targets 'would significantly reduce the risks and impacts of climate change'. Understanding the climate impacts of relatively low levels of warming, in particular whether there are substantial benefits to reducing emissions to limit warming to 1.5 °C rather than 2 °C, is important for informing climate policy, but such studies are scarce. Here we evaluate the difference in global biophysical and economic impacts related to agriculture between 1.5 °C-2 °C warming. Given the small difference in global average temperature, accounting for uncertainties is important, and we include key uncertainties in three main components of the analysis: climate system (regional climate variability), biophysical system (crop response to CO2 fertilization), and economic system (trade responsiveness). We are unable to meaningfully distinguish the regional agricultural impacts occurring with 1.5 °C warming from those occurring with 2 °C warming when accounting for these uncertainties. Under some assumptions 1.5°C implies benefits relative to 2 °C, while under others it implies costs. Results are most sensitive to the uncertainty in the effect of CO2 fertilization on crop yield.

Many countries are formulating a long-term climate strategy to be submitted to the United Nations Framework Convention on Climate Change by 2020. Model-based, multi-disciplinary assessments can be a key ingredient for informing policy makers and engaging stakeholders in this process.

The Paris Agreement does not only stipulate to limit the global average temperature increase to well below 2 °C, it also calls for ‘making finance flows consistent with a pathway towards low greenhouse gas emissions’. Consequently, there is an urgent need to understand the implications of climate targets for energy systems and quantify the associated investment requirements in the coming decade. A meaningful analysis must however consider the near-term mitigation requirements to avoid the overshoot of a temperature goal. It must also include the recently observed fast technological progress in key mitigation options. Here, we use a new and unique scenario ensemble that limit peak warming by construction and that stems from seven up-to-date integrated assessment models. This allows us to study the near-term implications of different limits to peak temperature increase under a consistent and up-to-date set of assumptions. We find that ambitious immediate action allows for limiting median warming outcomes to well below 2 °C in all models. By contrast, current nationally determined contributions for 2030 would add around 0.2 °C of peak warming, leading to an unavoidable transgression of 1.5 °C in all models, and 2 °C in some. In contrast to the incremental changes as foreseen by current plans, ambitious peak warming targets require decisive emission cuts until 2030, with the most substantial contribution to decarbonization coming from the power sector. Therefore, investments into low-carbon power generation need to increase beyond current levels to meet the Paris goals, especially for solar and wind technologies and related system enhancements for electricity transmission, distribution and storage. Estimates on absolute investment levels, up-scaling of other low-carbon power generation technologies and investment shares in less ambitious scenarios vary considerably across models. In scenarios limiting peak warming to below 2 °C, while coal is phased out quickly, oil and gas are still being used significantly until 2030, albeit at lower than current levels. This requires continued investments into existing oil and gas infrastructure, but investments into new fields in such scenarios might not be needed. The results show that credible and effective policy action is essential for ensuring efficient allocation of investments aligned with medium-term climate targets.

This paper presents a modeling comparison on how stabilization of global climate change at about 2 °C above the pre-industrial level could affect economic and energy systems development in China and India. Seven General Equilibrium (CGE) and energy system models on either the global or national scale are soft-linked and harmonized with respect to population and economic assumptions. We simulate a climate regime, based on long-term convergence of per capita carbon dioxide (CO 2 ) emissions, starting from the emission pledges presented in the Copenhagen Accord to the United Nations Framework Convention on Climate Change and allowing full emissions trading between countries. Under the climate regime, Indian emission allowances are allowed to grow more than the Chinese allowances, due to the per capita convergence rule and the higher population growth in India. Economic and energy implications not only differ among the two countries, but also across model types. Decreased energy intensity is the most important abatement approach in the CGE models, while decreased carbon intensity is most important in the energy system models. The reduction in carbon intensity is mostly achieved through deployment of carbon capture and storage, renewable energy sources and nuclear energy. The economic impacts are generally higher in China than in India, due to higher 2010–2050 cumulative abatement in China and the fact that India can offset more of its abatement cost though international emission trading.

Deep emission cuts rely on the use of low carbon technologies like renewable energy or carbon capture and storage. There is considerable uncertainty about their future costs. We carry out a sensitivity analysis based on Gauss Quadrature for cost parameters describing these technologies in order to evaluate the effect of the uncertainty on total and marginal mitigation costs as well as composition changes in the energy system. Globally, effects in total cost often average out, but different regions are affected quite differently from the underlying uncertainty in costs for key abatement technologies. Regions can be either affected because they are well suited to deploy a technology for geophysical reasons or because of repercussions through international energy markets. The absolute impact of uncertainty on consumption increases over the time horizon and with the ambition of emission reductions. Uncertainty in abatement costs relative to expected abatement costs are however larger under a moderate ambition climate policy scenario because in this case the marginal abatement occurs in the electricity sector where the cost uncertainty is implemented. Under more ambitious climate policy in line with the two degree target, the electricity sector is always decarbonized by 2050, hence uncertainty has less effect on the electricity mix. The findings illustrate the need for regional results as global averages can hide distributional consequences on technological uncertainty.

Deep emission cuts rely on the use of low carbon technologies like renewable energy or carbon capture and storage. There is considerable uncertainty about their future costs. We carry out a sensitivity analysis based on Gauss Quadrature for cost parameters describing these technologies in order to evaluate the effect of the uncertainty on total and marginal mitigation costs as well as composition changes in the energy system. Globally, effects in total cost often average out, but different regions are affected quite differently from the underlying uncertainty in costs for key abatement technologies. Regions can be either affected because they are well suited to deploy a technology for geophysical reasons or because of repercussions through international energy markets. The absolute impact of uncertainty on consumption increases over the time horizon and with the ambition of emission reductions. Uncertainty in abatement costs relative to expected abatement costs are however larger under a moderate ambition climate policy scenario because in this case the marginal abatement occurs in the electricity sector where the cost uncertainty is implemented. Under more ambitious climate policy in line with the two degree target, the electricity sector is always decarbonized by 2050, hence uncertainty has less effect on the electricity mix. The findings illustrate the need for regional results as global averages can hide distributional consequences on technological uncertainty.

Recent climate diplomacy efforts have resulted in Just Energy Transition Partnerships (JETPs) with South Africa, Indonesia and Vietnam, mobilizing financial support for ambitious decarbonization targets. Here, to assess JETPs’ alignment with global climate targets, we conduct a model-based assessment of JETPs’ energy and emissions targets. Results show greater alignment with a global 1.5 °C trajectory, indicating a promising route for international collaboration to keep Paris Agreement goals within reach. Just Energy Transition Partnerships (JETPs) are an important international initiative to address the urgent coal phase-out issue in emerging economies. Model-based assessment demonstrates JETPs for South Africa, Indonesia and Vietnam provide a promising route for achieving the 1.5 °C target.