As two of the most serious environmental problems China is facing, air pollution and climate change have been affecting China′s economic and social development in a growing manner. In terms of governance mechanism, the two problems have been managed by the Ministry of Environmental Protection and the Development and Reform Commission separately in the past. However, with the progression of relevant governance work, the mechanism of divide and rule gradually exposed overlaps problem and sometimes even conflictions, therefore innovation of collaborative governance mechanism is urgently needed. In 2018, China′s State Council implemented institutional reform, and the duty of dealing with climate change was transferred to the Ministry of Ecology and Environment, who immediately declared the need of collaborative governance of air pollution and climate change problems. What kind of mechanism can be established to ensure the realization of this strategic objective, has become a common concern of the political, academic and industrial circles.

The reason why air pollution and climate change were managed separately in the past, is that large differences exist in the form of how they affect the world while their inextricable connections were not obvious. On the one hand, mitigation of climate change is a long-term process with the needs of global efforts, and the damages it causes might be shown with significant time delays, therefore the cost-benefit of certain control measures is hard to be determined. While on the other hand, the damages caused by air pollution is normally limited to certain region and within certain time frame, and the effectiveness of air pollution control can be objectively evaluated by quantifying the degree of economic loss reduction and health improvements, which is relatively more definite and more straightforward. However, despite these large differences between the two, air pollution and climate change are actually two environmental problems sharing the same origin. Firstly, both are the results of the main emission sources - in the process of economic development, large-scale utilization of fossil fuel such as coal, oil and natural gas emits large number of air pollutants and greenhouse gases at the same time, resulting in air pollution and climate change respectively. Furthermore, there is a feedback relationship between the two. For one thing, as the main component of air pollutants, atmospheric aerosols are the mixture of particles of different sizes such as PM2.5, PM10 and various gaseous pollutants such as SO2, NOx, O3 and so on, which not only can cause air pollution, but also affect the radiation balance of the earth atmosphere or change the optical properties and life span of the clouds, and ultimately change the global climate significantly. For another, climate change can affect the secondary reaction of pollutants by changing their chemical reaction rate, and also disturb the transmission mode of atmospheric pollutants by changing the atmospheric circulation, thus aggravating the regional air pollution. It can be seen that governance of either air pollution or climate change would have an impact on the other, which proves that collaborative governance is feasible. 

In order to explore the effective mechanism of collaborative governance of air pollution and climate change, this paper attempts to: firstly, sort out the existing governance mechanism and sum up the problems of divide-and-rule; secondly, analyze the complex relationship between the two - same root, homology and mutual influence, and demonstrate the feasibility of collaborative governance; finally, propose an innovative collaborative governance mechanism as follows: (1) From the perspective of collaborative governance body, the Ministry of Ecology and Environment can give full play to its leading role in the administration of air pollution and climate change problems, timely clarify the overlapping of various relevant environmental equity trading systems, make up for a series of loopholes in the existing mechanism due to insufficient understanding of their connections, promote integration of management platforms to reduce execution costs, and use environmental regulation as an external pressure to force the enterprise ecosystem to improve operation efficiency and carry out environmental protection activities; (2) From the perspective of collaborative governance objects, special attention should be paid to the connection between the two which share the same root and of the same origin thus to accelerate the governance of the two with energy transformation being the driving force, take full advantage of past experiences to reduce the cost of governance, e.g. setting up of legal system of climate change can learn from the existing legal framework of air pollution prevention and control, while the handling of cross-border disputes related to air pollution can learn from the experience of climate change negotiations. In addition, attention must be paid to the interference of the relationship between the two. Taking the cooling effect of aerosols into account, a more prudent judgment should be made when formulating the carbon emission reduction plan. The uncertainty brought by climate change to the environmental capacity suggests that more attention should be paid to the usage of meteorological information. (3) From the perspective of collaborative goals, this mechanism aims to improve the efficiency of environmental governance of air pollution and climate change, which will accelerate the pace of energy transformation, so as to "decouple" economic growth from negative environmental externalities, balance the contradiction between environmental improvement and economic growth, and encourage green innovation to lead high-quality economic development.