Abstract: In the process of carbon mitigation, there is a intergenerational coordination of how much it will cost humanity to avoid possible future climate change. The answer to this question involves the interests of present and future generations, and requires a trade-off between the current costs and the future losses of carbon mitigation. However, the current international discussions on discount rates and intertemporal equilibrium paths have not yet resulted in a clear solution. There is an urgent need to form a carbon emission reduction path that integrates the long term and the short term. As part of the series of papers on the carbon mitigation “Time-Space-Efficiency-Benefit” (TSEB) coordination theory, this paper focuses on time coordination. It proposes an intertemporal equilibrium path and sets a positive but not aggressive discount rate, weighing the current cost of and the future loss caused of carbon mitigation. This paper analyzes the intertemporal responsibility sharing and cost allocation of carbon emission reduction, which is widely used in CEEP-BIT’s self-developed China’s Climate Change Integrated Assessment Model (C³IAM) and other studies on climate and environmental governance and carbon emission reduction pathways, providing a methodological basis for integrating long-term and short-term emission reduction.