Climate system is likely to collapse when such climate factor getting a tipping point under global warming, resulting in the consequences similar to the disaster film of “The day after tomorrow”. Permafrost degradation is considered as an important abrupt climate factor in the climate system. In the context of global warming, permafrost is rapidly deteriorating and will release a huge amount of carbon. Especially the emergence of permafrost thermokarst, combined with other climate tipping point factor, may reach the threshold of planetary boundary of the earth system within the IPCC target of 2 ℃, which will have an irreversible impact on the climate system.