Climate warming would increase the active layer thickness (ALT) of permafrost, which can cause changes in the hydrological cycle, ecological processes, and carbon flux in cold regions. However, changes in permafrost ALT due to climate warming remain poorly quantified, which limits our understanding of environmental change in cold regions. In this study, the Lund‐Postam‐Jena dynamic vegetation model is coupled to the Kudryavtsev model to examine changes in permafrost ALT on the Qinghai‐Tibet Plateau (QTP) under climate change scenarios based on the representative concentration pathways (RCPs). The results suggest that the permafrost ALT on the QTP would exhibit a significant increasing trend under the climate change scenarios, and a large increment of ALT may occur in the northwestern QTP. In the near‐term (2011–2040), the change in ALT on the QTP is different under the RCP2.6, RCP4.5, RCP6.0, and RCP8.5 emissions scenarios, with an increment of 5–30 cm. In the mid‐term (2041–2070), ALT would deepen further with an obvious reduction in permafrost area, while the increase in ALT decreases from south to north. In the long‐term (2071–2099), the average increment of ALT would be greater than 30 cm under the RCP4.5, RCP6.0, and RCP8.5 scenarios, and the increment in ALT increases from south to north, with a remarkable retreat in permafrost area from south to north.

Climate warming causes changes in permafrost distribution, which affects the surface energy balance, hydrologic cycle and carbon flux in cold regions. In this study, the Surface Frost Number model was applied to examine permafrost distribution on the Qinghai–Tibet Plateau (QTP) under the four RCPs (RCP2.6, RCP4.5, RCP6.0, and RCP8.5). The Kappa statistic was used to evaluate model results by comparing simulations of baseline permafrost distribution (1981–2010) with the existing frozen soil maps. The comparison shows that the Surface Frost Number model is suitable for simulating the general characteristics of permafrost distribution on the QTP. Simulated results suggest that areas of permafrost degradation would be the smallest in the near-term (2011‒2040) with the rates of 17.17%, 18.07%, 12.95% and 15.66% under RCP2.6, RCP4.5, RCP6.0 and RCP8.5, respectively. The rate of permafrost degradation would be faster in the mid-term (2041‒2070), especially under the RCP8.5 scenario (about 41.42%). Areas of permafrost degradation would be the largest in the long-term (2071‒2099) relative to baseline conditions, with a modelled 64.31% decrease in permafrost distribution using the RCP8.5 scenario. Our results would help the decision‒making for engineering construction program on the QTP, and support local units in their efforts to adapt climate change.

Based on the normalized difference vegetation index (NDVI), we analyzed vegetation change of the six major biomes across Inner Mongolia at the growing season and the monthly timescales and estimated their responses to climate change between 1982 and 2006. To reduce disturbance associated with land use change, those pixels affected by land use change from the 1980s to 2000s were excluded. At the growing season scale, the NDVI increased weakly in the natural ecosystems, but strongly in cropland. Interannual variations in the growing season NDVI for forest was positively linked with potential evapotranspiration and temperature, but negatively correlated with precipitation. In contrast, it was positively correlated with precipitation, but negatively related to potential evapotranspiration for other natural biomes, particularly for desert steppe. Although monthly NDVI trends were characterized as heterogeneous, corresponding to monthly variations in climate change among biome types, warming-related NDVI at the beginning of the growing season was the main contributor to the NDVI increase during the growing season for forest, meadow steppe, and typical steppe, but it constrained the NDVI increase for desert steppe, desert, and crop. Significant one-month lagged correlations between monthly NDVI and climate variables were found, but the correlation characteristics varied greatly depending on vegetation type.

Effects of permafrost degradation on carbon (C) and nitrogen (N) cycling on the Qinghai‐Tibetan Plateau (QTP) have rarely been analyzed. This study used a revised process‐based biogeochemical model to quantify the effects in the region during the 21st century. We found that permafrost degradation would expose 0.61 ± 0.26 (mean ± SD) and 1.50 ± 0.15 Pg C of soil organic carbon under the representative concentration pathway (RCP) 4.5 and the RCP 8.5, respectively. Among them, more than 20% will be decomposed, enhancing heterotrophic respiration by 8.62 ± 4.51 (RCP 4.5) and 33.66 ± 14.03 (RCP 8.5) Tg C/yr in 2099. Deep soil N supply due to thawed permafrost is not accessible to plants, only stimulating net primary production by 7.15 ± 4.83 (RCP 4.5) and 24.27 ± 9.19 (RCP 8.5) Tg C/yr in 2099. As a result, the single effect of permafrost degradation would cumulatively weaken the regional C sink by 209.44 ± 137.49 (RCP 4.5) and 371.06 ± 151.70 (RCP 8.5) Tg C during 2020–2099. However, when factors of climate change, CO₂ increasing and permafrost degradation are all considered, the permafrost region on the QTP would be a stronger C sink in the 21st century. Permafrost degradation has a greater influence on C balance of alpine meadows than alpine steppes on the QTP. The shallower active layer, higher soil C and N stocks, and wetter environment in alpine meadows are responsible for its stronger response to permafrost degradation. This study highlights that permafrost degradation could continue to release large amounts of C to the atmosphere irrespective of potentially more nitrogen available from deep soils.