*Review* **A Scientometric Analysis and Review of the Emissions Trading System**

**Yu-Jie Hu 1,2,\* , Lishan Yang <sup>1</sup> , Fali Duan <sup>2</sup> , Honglei Wang 1,3 and Chengjiang Li 1,4**


**Abstract:** As a vital market mechanism to mitigate global warming, the emissions trading system (ETS) has critical research and practice value. According to articles from Web of Science's core collection, quantitative statistics are used to analyze the ETS, including statistics on the number of articles, distributions of time and geography, journals and subjects, productive authors and institutions, academic collation, article citations, and hot topics. Moreover, this paper presents a qualitative analysis of research on the ETS, exploring hot issues, including its origin, allowance allocation, the impact of allowance allocation, and the ETS in the power sector. The results show that it is necessary to launch ETS to mitigate climate change effectively and reduce emissions at a low cost. Allowance allocation as its critical component has also caused heated discussion among scholars. In allowance allocation, exploring a desire to assign the future allowable carbon emissions reasonably and efficiently is vital, yet scholars widely do not accept this. Moreover, free allocation can only be applied to the transitional stage, and auctioning will be inevitable. In addition, scholars have studied the impact of different allowance allocation schemes from macro and micro perspectives and take the power sector, namely the largest emitter, as an example, by linear programming, equilibrium modeling, and multi-agent modeling. However, the quota allocation scheme needs improvement due to firms' accuracy of emission data. Finally, governments are encouraged to launch the ETS to reduce emissions and combat climate change. The ETS should be improved gradually, including aspects such as cap setting, covering sectors, and the allocation method. Additionally, some key emission sectors and regions can be taken as the research and practice objects in the initial stage of the ETS.

**Keywords:** emissions trading system; allowance allocation; quantitative statistics; qualitative analysis
