The active layer, which freezes in dead season and thaws in warm season every year, is the rock and soil layer at crustal derm. Seasonal change of active layer thickness depends on the climate, and it is related to the altitude, latitude, lithology of active layer, characteristic of containing water, soil heat flux, and characteristic of terrain and underlying surface. The change of the active layer thickness, which affects the ecological environment in cold region, is the most active factor. The active layer thickness and the dynamic change processes of water and heat in permafrost region affect the processes of biology, physics and geochemistry of the system of hydrology and ecology. Meanwhile, with the increasing of active layer thickness, the organic carbon and greenhouse gases, which deposited in the permafrost, will release into the atmosphere gradually. It will affect the local area and even the global climate change. 

Based on the climate change Scenarios A1B, A2 and B1, researchers predict the changes of the active layer thickness by the Stefan’s Equation for the permafrost regions on the Tibetan Plateau in Southwest China. It is found that the active layer depth will increase radically outwards from the Qiangtang basin in the interior of the Tibetan Plateau with rising air temperature under the projected climate scenarios. Changes in the active layer thickness under scenarios A1B and A2 will be more significant than that under scenario B1, because of lesser anthropogenic impacts. In 2050, the mean active layer thickness will reach 3.07m under Scenario A1B, about 0.3~0.8m more than that in 2010. At the same time, the increment will be 0.2~0.5m under Scenario B1 and 0.2~0.55m under scenario A2. In 2099, the mean active layer thickness will reach 3.42m under scenario A1B, 3.53m under scenario A2, and 2.93m under scenario B1. Climate warming will significantly deepen the active layer. One hundred years later, the spatial distribution of permafrost will change largely. 

The research program was co-funded by the National Major Scientific Research Project (2010CB951402) and the Important Direction Group Project of CAS. The research achievement was published in the Journal of Glaciology and Geocryology.