基于博弈论的全球减排合作方案

Global cooperation on carbon mitigation by applying game theory

本文提出了一个新的全球碳减排合作原则,并在博弈分析的框架下,用集成评估模型EMRICES平台模拟计算,给出了一个全球减排合作方案.该方案首先可以保证2100年全球升温不超过2℃目标,并可以实现各国的累积福利比没有减排约束下的结果好,即具有帕累托改进特性.此外,该方案还在帕累托改进原则的基础上考虑了基于"共同但有区别"的公平问题.最后,本文针对重要参数贴现率做了敏感性分析.结果显示,贴现率的变动不影响非合作的纳什均衡,但会改变方案的帕累托改进的解集.具有更高贴现率的国家,其帕累托改进的空间将越小.由于贴现率的大小在一定程度上取决于消费增长速度,且许多发展中国家的消费增长速度高于发达国家,因此本文认为在国际气候谈判中,需要考虑发展中国家与发达国家之间存在的贴现率差异,从而更好地体现全球减排合作的公平.

The global carbon emission mitigation schemes would mainly determine the trends of global climate change and the global economic growth. Although many mitigation schemes were proposed by scholars and institutions, seldom of the schemes seem to satisfy countries all around the world. It is quite urgent to find a solution to mitigate climate change, which should also be acceptable by the world. Therefore, a global carbon mitigation scheme is proposed and simulated in this paper by employing game theory and using the integrated assessment model, EMRICES. Game theory is used to analysis the ＂free-riding＂ behaviors for setting the mitigation scheme. The mitigation scheme firstly grantees that the increase of global temperature is no more than 2℃ till 2100. Secondly, every country participating in the scheme would benefit from the scheme comparing with the situation when there is no carbon reduction request, which is called Pareto improvement principle. Accumulated welfare is used as the index and it is a function of consumptions. Thirdly, the fairness of mitigation scheme is taken into consideration as well in the scheme according to the ＂common but differentiated responsibilities＂ principle. The Pareto improvement principle and the common but differentiated responsibilities principle may be incompatible sometimes. If developed countries＇ interest is adequately safeguarded, developing countries would usually bear more carbon reduction. Thus, when searching for the mitigation scheme, the two principles both as objectives are given different priorities. The Pareto improvement principle is given the primary priority. As for the common but differentiated responsibilities principle, we try to minimize the developed countries＇ accumulated welfares improvement and maximize the developing countries＇. The scheme was searched as following＂ China should reduce 20% carbon emissions of 2005＇s level by 2050; USA should reduce 63% carbon emissions of 1990＇s level by 2050; Japan should reduce 85% carbon emissions of 1990＇s levels by 2050; EU should reduce 85% carbon emissions of 1990＇s levels by 2050; high developed countries should reduce 50% carbon emissions of 2005＇s levels by 2050; middle developed countries should reduce 20% carbon emissions of 2005＇s levels by 2050; developed countries should reduce 82% carbon emissions of 1990＇s levels by 2050. All the countries should keep the carbon emission level no more than 2050＇s after 2050. As the result shows, the global temperature increases by 1.996℃ in 2100. The global temperature increment can be controlled within 2℃. All the countries＇ or regions＇ accumulated welfares are improved and developing countries obviously improve more than developed countries. In a word, we find a scheme that satisfies the three requirements. Finally, sensitive analysis is conducted for the important parameters. The results show that the variation of discount rate will not change the no-cooperation Nash equilibrium but it does affect the Pareto improvement solution. The higher the discount rate is, the harder would be to achieve the Pareto improvement. Developing countries＇ discount rates are generally higher than developed countries＇ due to the different economic consumption＇s growth rate among the countries. Thus, this factor should be considered as well in global climate negotiations for fairness.