Equitable Sharing In National Mitigation Contributions To Achieve The Paris Agreement Ambitions

The "Paris Agreement" signed in 2015 established a global climate governance architecture in which countries determined their own mitigation contributions.However,the collective Nationally Determined Contributions(NDC)proposed by all the countries are insufficient to meet the emission requirements for realizing 2? and 1.5? targets.There continues to be deep divisions on how to share the mitigation contributions in an equitable manner,which is a very important foundation for all countries to cope with climate change in the future.How to safeguard the achievement of the Paris climate ambitions and enhance the national contributions is the hot topic in current global climate governance.This core issue includes:setting benchmarks for all countries as their NDC reference so as to strengthen their contributions,bridging the equity conflicts in the international community to avoid a deadlock of determining the effort-sharing mechanism,and analyzing the cooperation opportunities and conflict risks in future negotiations for better multilateral collaboration.In this work,comprehensive,consistent,and unbiased data sets of future emission allocation pathways of each country are firstly estabilished.By using multidisciplinary methods including Optimization Methods,Data Mining techniques and Operations Research,a feasible benchmark for each country to assesse their gaps in NDC efforts is determined quantitatively based on the principles of fairness and equally-distributed extra efforts;the correaltions between future emission allocation pathways and allocation schemes are systematically and dynamically analyzed;through global allocation scenario analysis,the future cooperation opportunities between countries in climate negotiations are identified,all of which are quite important for instructing countries to fairly compensate the gap so as to achieve the temperature-rising objectives of the Paris Agreement.The study shows that,(1)For the 2? target,128 countries are expected to increase their NDC in 2030,and China,India,USA and EU28 respectively fall short by 4.49-5.91,0.38-1.78,1.39-1.52 and 0.68 Gt CO2eq in their NDCs efforts in 2030;as for 1.5? target,all the 195 countries need to strengthen their NDC.From 2? to 1.5? target,China's share in making up the global shortfalls changes from 31%to 26%.(2)For the 2? target,developing countries group needs to peak in 2020 and return to 2010 levels in 2030,and to 65%of 2010 emissions by 2050.The peaking of developing group in 2020 essentially depends on China,increasing by 10.4%relative to 2010 levels by then.Developed countries group should reduce emissions by 50%of 2010 emissions in 2030,and continue to achieve 33%reductions of 2010 levels by 2050.(3)Cluster analysis of 1542 allocation schemes over multiple years shows that there are similarities between allocation schemes under different fairness principles,while heterogeneities are observed between sub-schemes under the same basic allocation scheme,indicating a non-corresponding correlation between the emission allocation pathways and the allocation schemes under 2? target.Therefore,instead of continuing to entangle the choice of the effort-sharing mechanism,the future climate negotiations are supposed to improve the result orientation to the Paris ambitions.(4)Through a variety of allocation scenarios analysis,it is found that China is supposed to strengthen the negotiation synergies with India due to the consistent emission quota relations,pay attention to the turning standpoint of Brazil,South Africa and small island countries due to the opposite emission quota relations,and try to improve the cooperation with OPEC countries,who are not affected in allocation scenarios guided by principles of responsibility,capability and corrective equality,and also Russia,who is different with other developed countries in allocation scenario of equality,so as to strengthen the multilateral collaboration ultimately.