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As a complement of production-based accounting (PBA), consumption-based accounting (CBA) provides an alternative perspective to understand national emissions and responsibilities for global climate change. Existing studies assessed historical national emissions under CBA. However, how CBA might guide future mitigation under the Paris Agreement goals has not been well understood. By combining global multi-region input-output analysis and the equity principle of 'equal cumulative per capita emissions' (ECPCE), this study explores potential implications of CBA for future national emissions budgets to limit global warming to below 1.5°C. Historically, consumption-based greenhouse gas (GHG) emissions were higher than production-based emissions in most developed countries while lower in many developing countries. When CBA is used instead of PBA to allocate emissions budgets by ECPCE, future GHG mitigation burdens would become more stringent in 70% of Annex I (mostly developed) countries but slightly smaller in 55% of non-Annex I (mostly developing) countries. In particular, more than half of Annex I countries might need to achieve negative GHG budgets under 1.5°C. Our analysis emphasizes that, as net emission importers, developed countries could strive to pay equal attention to achieving consumption-based and production-based emissions reductions, and strengthen technological and financial support to developing countries that undertake production outsourcing. As net emission exporters, with international support and domestic investment, developing countries could pragmatically promote energy structure optimization and technological innovation to accelerate the decarbonization of production. To support the Paris Agreement goals, mitigation contributions initiated from the perspective of CBA could also be welcomed. Key policy insights Developed countries shift emissions to developing countries through international trade. CBA increases historical responsibilities of developed countries for climate warming from the PBA assessments. Compared to PBA, CBA has clear implications on future national emissions budgets under responsibility-based allocations, but does not change the urgency of national mitigation required to achieve the Paris Agreement goals. Allocated by ECPCE, future GHG budgets for over 50% of the world's countries would be run out before 2040 under 1.5°C at the 2015 emissions rates, using either CBA or PBA. According to different roles in global supply chains, developed countries should step up support to help developing countries improve emissions and energy intensities, which is a key to reducing emissions embodied in trade. [ABSTRACT FROM AUTHOR]

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Understanding the drivers of CO2 emissions changes is useful in supporting future mitigation. This study applies a log-mean divisia index decomposition to assess four drivers of CO2 emissions changes – population, income, energy intensity and carbon intensity – in 138 countries worldwide over the period 2000–2017. At the global level, income and population are the main drivers of increased emissions over time, with contributions of 116% and 60% to global CO2 emissions changes, respectively. Energy intensity is the key mitigation driver, with a contribution of −80%. Although carbon intensity increased CO2 emissions overall over the period 2000–2017 with a contribution of 4%, it has started to reduce emissions in recent years. China, the United States of America, the European Union, India and Russia are the five regions responsible for most changes in global emissions. The five regions together contribute −73% of the energy intensity effect, and China's income contribution is 83% in relation to the total of 116%. At the national level, in 2017, CO2 emissions returned to below 2000 levels in 62% of Annex I (developed) countries but increased in 88% of non-Annex I (mostly developing) countries. Among the 35 countries realizing CO2 emissions reductions, 24 were driven primarily by energy intensity, six by carbon intensity, three by economic recession, and one by population decrease. Among the 103 countries with increasing CO2 emissions, 63 were driven primarily by income, 26 by population, nine by carbon intensity increase, and five by energy intensity increase. Our analysis emphasizes the necessity of considering differences in national development stages when formulating climate change mitigation policies. Key policy insights Over the period 2000–2017, at the global and national levels, CO2 emissions increases were driven mainly by economic development and population growth, and mitigation was driven mainly by energy intensity improvement. Improving energy intensity and carbon intensity is the key to mitigating CO2 emissions. Carbon intensity is expected to play an increasing role in the future. In over one-third of Annex I countries, CO2 emissions increased from 2000 to 2017. To meet the Paris Agreement goals, Annex I countries will need to enhance mitigation ambition by further tapping the mitigation potentials of energy and carbon intensity. In accordance with national circumstances, development needs and international support, non-Annex I countries should achieve low-carbon economic and energy transitions and peak CO2 emissions as early as possible. [ABSTRACT FROM AUTHOR]

Comparing and evaluating the Nationally Determined Contribution (NDC) is an important element in global stocktake in the post-Paris climate negotiations, aimed at closing the emissions gap with the Paris Agreement goals. To date, however, there has still been no explicit guideline or method. By applying emissions allowance allocated by 16 schemes as benchmarks, this paper tries to compare and evaluate the NDCs of the top six emitters, which jointly account for about 70% of the world’s CO2 emissions. Results show that the four developed countries’ NDCs lack ambition with respect to most allocations under 2°C and all under 1.5°C, indicating they need to substantially ratchet up their NDCs and lead elevating mitigation. Evaluating cumulative emissions is more likely to clarify the ambition and fairness of China’s NDC. If considering cumulative emissions, China’s NDC is aligned with the median of cumulative allowances under 2°C and within the 1.5°C range. The Paris Agreement invited the Parties to communicate the mid-century low emissions strategies. This paper also tries to explore the mid-century mitigation in the perspective of allocations, which might provide decision-makers with some useful information when envisaging the post-NDC mitigation. [ABSTRACT FROM AUTHOR]

The Kyoto Protocol inspires the idea of establishing emissions trading scheme, regarding economic-effectiveness as a significant factor to achieve reduction targets and meet obligation. With this trend, marginal abatement cost curves (MACCs) have been used in climate policy analysis under general equilibrium framework, and have been proved a valid device to highlight the superiority of ETS. This paper focuses on the comparison of MACCs at industry level in China, derived by us from CGE, GCAM and TIMES respectively. It's clear that there is no dynamic adjustment process in these models, so we use linear interpolation method to introduce carbon tax to simulate actual situation. Meanwhile, we also take data from potential and cost study into account. To make our work more targeted, we pay close attention to energy-intensive industries with high carbon emissions level such as electricity, cement and steel, which are most likely to be covered in carbon market. The results indicate how MACCs change and illustrate why they change, depending on applied methodology and underlying assumptions. As we ignore the indirect effects, for instance, tax distortions and non-financial costs during above simulation, the emissions abatement cost we achieve by using integral calculus won’t be equivalent to real cost. Therefore, it's a wise decision for government department and research institute to be cautious when using MACCs as basis of policy making and academic studies. [ABSTRACT FROM AUTHOR]

Towards a low carbon world, the global emission space in the future will be very restricted, which will have a significant impact on the deployment of energy infrastructure system. A low carbon energy system will be the key to achieve 2 degrees trajectory. This paper addresses this issue by combining the Equitable Access to Sustainable Development model (EASD) and the Global Change Assessment model (GCAM) to analyze the development of regional energy consumption and power generation in the process of combating climate change. GCAM, a dynamic-recursive integrated model, has divided the world into 14 regions. Under the long term targets resulting in harmonized radiative forcing levels, the carbon constraints of all regions are quantified in EASD through the allocation based on the per capita, the convergence and the status-quo basis, respectively. These constraints are then set as the policy scenarios in GCAM simulations. The findings underline the substantial reductions in coal consumption and huge growth in renewable energy and nuclear in all regions. The fossil fuel consumption of developed regions has to plummet at once on the per capita basis and peak before 2020 on both the convergence and the status-quo basis. In developing regions, the nuclear and the coal/gas with carbon capture and storage (CCS) gradually dominate the power supply. CCS and nuclear are the two main technology choices for electricity generation in developed regions. [ABSTRACT FROM AUTHOR]

As a major technical route to utilize biomass energy, biomass combustion power generation (BCPG) has been shown to be of environmental and economic significance. According to the operating experience, the installed capacity has a decisive impact on the operation and economic return of BCPG projects. In China, an installed capacity of either 30 MW or 12 MW is often chosen for constructing a BCPG project. To explore which one is more suitable for China, this paper uses actual operating data to compare the operation performance and techno-economics of two representative BCPG projects with an installed capacity of 30 MW and 12 MW. The results show that the operation situation and electricity production of the 30 MW project are better than those of the 12 MW project. The 30 MW project has a lower biomass consumption than the 12 MW project to produce per unit of electricity. The Internal Rate of Return (IRR) of the 30 MW project is greater than the industry benchmark in China and is almost three times the IRR of the 12 MW project. Therefore, it is recommended to construct BCPG projects with installed capacity of 30 MW in China. [ABSTRACT FROM AUTHOR]

With the increasing competition for limited metal ore resources, nexus between economics society and mineral resource utilization has been studied broadly. However, the driving forces and pathways of metal footprint change still haven't been fully understood. Therefore, in the present study, the additive structural decomposition analysis based on an environmental input-output model is adopted to decompose the world metal footprint from 1995 to 2013 into five major driving factors: metal consumption intensity effect, production structure effect, category effect, consumption patterns effect and consumption volume effect. The obtained results indicate that: i) the modern production structure has been becoming increasingly dependent upon metal resources; ii)the production structure effect and consumption volume effect are dominant factors driving the metal footprint increase, yet the metal consumption intensity effect is the main force offsetting this inclining trend; iii) distinct patterns can be observed among different kinds of metals due to the production structure effect; iv) all the driving factors in developing countries tend to be more divergent comparing with developed countries consistent with their economic growth characteristics. The findings of this study are significant for policy makers to understand the deep causes for domestic metal footprint change and propose proper relevant polices. [ABSTRACT FROM AUTHOR]