Abstract: Since climate change is one of the important factors causing desertification, to study climate change background in the Qinghai-Tibet Plateau is the foundation of the desertification research. Based on daily data of the 81 meteorological stations in Qinghai-Tibet Plateau from 1971 to 2011, the characteristics of decadal climate change in the Qinghai-Tibet Plateau during 41 years is analyzed. The results show that the Qinghai-Tibet Plateau became warmer and wetter after the late 1990s with the increments of temperature and precipitation. During the same period, the average wind speed slowed down from the decline tend, the variation tend of relative humidity converted from increase to obvious decrease, and the insolation dropped greatly since the 1980s, but became an upward trend in the 21st century. Because of the interaction of the five factors, potential evaporation showed an obvious turning point from the downward trend into an upward trend in the late 1990s. Therefore, the late 1990s is an important node for the plateau climate change. The boundaries of wet climate and dry climate in the plateau had a significant decadal fluctuation. There were differences in diversification of different zones, and the overall performance for all the lines was moving to the northwest. The extremely arid region, arid area reduced, semi-arid region, sub-humid zone and humid area increased. The index of wet and dry line met the plateau desertification boundary, so the wet and dry boundary's fluctuations may reflect the desertification change in the plateau.

Key words: Qinghai-Tibet Plateau, climate change, dry and wet conditions