Permafrost has significant impacts on climate change through its strong interaction with the climate system. In order to better understand the permafrost variation and the role it plays in climate change, model outputs from Phase 5 of the Coupled Model Intercomparison Project (CMIP5) are used in the present study to diagnose the near-surface permafrost on the Tibetan Plateau (TP), assess the abilities of the models to simulate present-day (1986-2005) permafrost and project future permafrost change on the TP under four different representative concentration pathways (RCPs). The results indicate that estimations of present-day permafrost using the surface frost index (SFI) and the Kudryavtsev method (KUD) show a spatial distribution similar to that of the frozen soil map on the TP. However, the permafrost area calculated via the KUD is larger than that calculated via the SFI. The SFI produces a present-day permafrost area of 127.2 x 10(4) km(2). The results also indicate that the permafrost on the TP will undergo regional degradation, mainly at the eastern, southern and northeastern edges, during the 21st century. Furthermore, most of the sustainable permafrost will probably exist only in the northwestern TP by 2099. The SFI also indicates that the permafrost area will shrink by 13.3 x 10(4) km(2) (9.7%) and 14.6 x 10(4) km(2) (10.5%) under the RCP4.5 and RCP8.5 scenarios, respectively, in the next 20 years and by 36.7 x 10(4) km(2) (26.6%) and 45.7 x 10(4) km(2) (32.7%), respectively, in the next 50 years. The results are helpful for us to better understand the permafrost response to climate change over the TP, further investigate the physical mechanism of the freeze-thaw process and improve the model parameterization scheme.

Wilhelm et al. (2015) employed the widely used Stefan and Kudryavtsev equations to predict the maximum active-layer thickness (ALT) on Amsler Island, Western Antarctic Peninsula. Their predictions far exceed the observations of ALT reported from other parts of the region. Here, I demonstrate that the values of ALT are significantly overestimated by the predictive equations because the authors incorrectly assumed that little or no latent heat of phase change is absorbed during thawing. Although the area is the warmest in the Antarctic Peninsula region, with a rapid increase in air temperature and permafrost temperatures close to 0 degrees C, the active layer is likely to be substantially thinner than values predicted by Wilhelm et al. (2015). Copyright (c) 2016 John Wiley & Sons, Ltd.