Abstract: Under the background of global warming, extreme temperature changes have become a serious threat to Tibetʼs economic and social development and ecological and environmental protection. Based on the daily maximum and minimum temperature in Tibet from 1971 to 2018, and 12 extreme air temperature indices recommended by international ETCCDI were computed to reveal the temporal and spatial variations of extreme temperature in Tibet. The results showed that, in the past 48 years, the cool days, cool nights, ice days, frost days, and diurnal temperature range in Tibet showed a downward trend, and the warm days, warm nights, summer days, max T_max, max T_min, min T_max, and min T_min showed an upward trend, and the changes were more obvious after the 1990s. The extreme temperature index （cold indices and warm indices） showed an asymmetric change in time, and the change range and rate of the cold indices were higher than the warm indices. Most extreme temperature indicators showed obvious changes from southeast to northwest. The most extreme temperature indices had no obvious correlation with longitude and latitude. Except that cool days, cool nights, warm days and diurnal temperature range had no obvious relationship with altitude, the other extreme temperature indexes were significantly related to altitude.

Key words: extreme temperature, temporal and spatial variation, Mann-Kendall test, Tibet