Quantifying air temperature evolution in the permafrost region from 1901 to 2014

Permafrost is sensitive to climate change. In recent decades, a growing body of research has focused mainly on the study of permafrost thaw, but leaving the climate change in the permafrost region that has not been adequately assessed, which is of first importance for the research on permafrost thaw. Using gridded observations from the Climatic Research Unit (CRU), in conjunction with the European Centre for Medium-Range Weather Forecasts Reanalysis Interim (ERA-Interim) and Japanese 55-year Reanalysis (JRA-55) data, this study investigates characteristics of air temperature evolution in the region of permafrost throughout the 20th century. Results show that yearly air temperatures in the permafrost region of the Northern Hemisphere experienced a statistically significant warming, with trends of 0.13 degrees Cdecade(-1) for 1901-2014 and 0.40 degrees Cdecade(-1) for 1979-2014. Winter air temperatures showed the greatest increase during 1901-2014, while autumn air temperatures increased the most during 1979-2014. In addition, increases in air temperature in high-latitude permafrost sub-region are greater than those in high-elevation permafrost sub-region, and air temperatures in the permafrost sub-region of Mongolia have the largest trend from 1901 to 2014, followed by those in Russia, Alaska, Canada, and China. Air temperatures in the permafrost region increased 1.7 times more than temperatures globally from 1901 to 2014, and underwent an increase at a rate of 0.32 degrees Cdecade(-1) during the period 1998-2014, when the global warming hiatus occurred with a trend of 0.06 degrees Cdecade(-1). This implies that permafrost thaw may have continued during the global warming hiatus period. The close agreement between CRU data and ERA-Interim and JRA-55 reanalysis data indicates good reliability of air temperature evolution characteristics. These results provide information relevant to climate change in the permafrost region, and are useful for researching and understanding historical permafrost change.