Cost-Effective Pathways Toward The Paris Agreement Targets And The Reaction Of China’s Energy Transition

As increasing global warming continues to impact human life and socio-economic development,countries need to carry out temperature control actions to reduce the adverse effects of warming.After the Paris Agreement provided a unified direction for global climate change mitigation,how to achieve the agreement’s temperature targets has become a hot issue in the fields of climate,economy,and energy.Countries need to adopt different emission reduction strategies due to differences in socio-economic development and technological endowments,and cost-effective principles can help these countries work together to achieve the Paris Agreement’s temperature targets based on reconciling the interests of all parties.The regional energy transition is one of the crucial ways to help achieve the Paris Agreement’s temperature targets.China’s fossil-dominated energy use pattern needs to be reasonably optimized to effectively leverage China’s energy transition to achieve the Paris Agreement’s temperature control targets cost-effectively.Although existing studies have paid sufficient attention to the necessity and feasibility of the Paris Agreement temperature targets and their requirements for optimal transformation of the energy system,the characteristics of regional emission reduction pathways and realization options for the cost-effective achievement of the temperature targets need to be further enriched;meanwhile,there are not many studies on how the energy system can adapt to climate mitigation actions.Therefore,how to provide suitable regional-scale major GHG emission reduction pathways for the Paris Agreement temperature targets and how to provide regional-specific solutions for compliance with the Paris Agreement temperature targets from the perspective of China’s energy system transition reaction are the main concerns of this study.Based on this,the thesis takes the Paris Agreement temperature target cost-effectively into account.It systematically sorts out the mechanism of the role of temperature target achievement and energy transition in climate change mitigation.Then,based on research theories such as energy substitution theory,complex system theory,and climate change economics theory,and integrates tools such as integrated assessment model,computable general equilibrium model,and marginal abatement cost curve to clarify.Based on this framework,a framework for assessing and verifying the marginal abatement costs and abatement potential of temperature control actions is constructed,and the characteristics of regional abatement pathways for achieving cost-effective temperature control targets are analyzed.The future long-term transformation direction of China’s energy from the perspective of energy system reaction is proposed.Specifically,this dissertation addresses the following aspects:（1）Using the Paris Agreement temperature control target of 1.5°C as an example,the thesis explored the differences and characteristics of the warming impacts of greenhouse gases and air pollutants in China,and identified the critical emission sources that affect China’s share of warming.By collating China’s emission reduction pathways under this temperature target from different model outputs,the ACC2 model is used to calculate the warming impact results for China in general and for a single gas and analyze the common features,give the critical gas emission sources and important time points for emission reduction actions in China,and then analyze how to effectively reduce the impact of crucial emission sources to reduce their effectiveness on global warming,taking CH₄ emission reduction as an example.The results show that CO₂,CH₄,and SO₂ are the primary sources of warming in China,while N₂O and HFC also significantly impact warming levels,and deep CH₄emission reduction is a crucial task for the energy system soon.China’s peak average warming impact level to achieve the 1.5°C target is 0.17°C（range 0.099-0.223°C）.In addition to CO₂,CH₄ and SO₂ also significantly affect China’s ability to meet global temperature targets.However,SO₂ emissions exhibit a cooling effect while the impact has already peaked,but the peak warming impact of CH₄ is achieved around 2030,so near-term reductions in CH₄ can effectively reduce the magnitude of China’s contribution to the peak increase in global warming.（2）The marginal abatement costs and abatement potential of multi-scale climate mitigation actions under the Paris Agreement temperature targets were estimated,and the heterogeneity characteristics of the marginal abatement cost curves of the three major GHGs in different regions were explored.After collecting and collating the emission reduction paths of ENGAGE database and GET model under the given carbon emission allowance or carbon price constraints,a multi-scale marginal abatement cost assessment framework was constructed using the marginal abatement cost curve approach to evaluate the abatement potential and marginal abatement cost of different gases,policies,emission sources and regions,and the validity of the framework was verified by combining the economic module of ACC2 model,which can provide a relatively fair distribution scheme for different areas to bear the temperature control contribution.The results show that although China has a high potential for GHG emission reduction,the marginal cost of emission reduction is not low for the same level of emission reduction.Although there are significant differences in the marginal abatement cost curves between models,in general,the marginal abatement cost curves for all three gases in China are higher than the global-scale marginal abatement cost curves,while the three regions（i.e.Latin America,reforming economies,and South Asia）still have low marginal abatement costs at high abatement levels and should be considered as priority regions for future GHG abatement strategies.（3）The spatial and temporal differences in abatement costs for the cost-effective achievement of different temperature control targets of the Paris Agreement are analyzed,and the impact of China’s carbon neutrality target on abatement costs and temperature control effectiveness is explored.Based on the equitable distribution principle of cost-effectiveness,a series of temperature control target scenarios are constructed from the perspective of global and long-term cost-effectiveness for temperature,overshoot,compliance time,and negative emissions.A cost-minimizing regional abatement scenario is given using the ACC2-em IAM model,based on which China’s 2060 carbon neutrality target is added as a new constraint to assess the impact of this commitment on abatement costs and temperatures for different temperature targets.The results show that China’s contribution to the cost-effective emission reduction scenario is significantly different from that of other regions and that China’s carbon-neutral target is more compatible with the Paris Agreement’s 1.5°C temperature control target.Compared to the 2°C temperature target,a cost-effective 1.5°C target would double the global abatement cost,with China bearing a much higher share of the abatement than other regions and a higher responsibility for the reduction in the near term than in the long term,and the impact of the abatement cost on the regional economy becoming larger and then smaller over time,with a tighter target constraint corresponding to an earlier impact inflection point.In addition,a cost-effective pathway to achieving the Paris Agreement temperature targets does not require net zero for all regions.（4）Analyzing the response characteristics of China’s energy transition under the cost-effective pathway constraint to achieve the Paris Agreement temperature target and optimize the transition pathway of China’s energy system in terms of energy market supply and demand,capital flows,and deployment of emission reduction technologies.By using the cost-effective achievement of the temperature control target as a constraint,the cost-effective emission reduction results generated by ACC2-em IAM are input into the AIM/CGE model to derive a Chinese energy transition pathway scenario to the end of this century under different cost-effective trajectories in achieving the target.The results show that China’s natural gas-based energy use system will not be able to support the achievement of the Paris Agreement’s temperature targets.Solar,wind,and bioenergy will need to be the dominant forms of energy use in China in the future.Energy supply-side investments depend on the intensity of the temperature target,and energy investments flow mainly to the power sector.The 1.5°C target requires immediate peak primary energy consumption,while the peak energy consumption required for the 2°C target is achieved in 2040-2050.The 1.5°C requires enhanced CCS deployment actions earlier than the 2°C target,yet the 2°C requires higher CCS emission reductions,while the net-zero emission constraint would bring deployment actions further forward.Based on the above results and findings,this thesis proposes a series of policy recommendations to promote adaptation costs better to effectively achieve the Paris Agreement temperature targets,to promote the development of renewable energy industries to match the temperature targets,and to help China advance global climate change mitigation actions for temperature control and emission reduction.The main contributions of this thesis are 1)a consistent methodological framework to evaluate the temperature response of China’s 1.5°C target emission pathways generated by different IAMs and identify key emission sources,complementing the studies on the warming response mechanism of China’s net-zero pathways;2)a multi-scale marginal abatement cost curve generation and validation framework and exploration of the cost-effective of achieving the Paris Agreement temperature targets,which enriched the research on cost-effective abatement at a regional scale;3)explored the long-term transition pathways and response characteristics of China’s energy system under the guidance of cost-effective achievement of Paris Agreement temperature targets,which enriched the research on regional energy transition under temperature targets.