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Abstract: The northwest region in China is vast, with administrative divisions including parts of Shaanxi, Gansu, Ningxia, Qinghai, Xinjiang, and Inner Mongolia. Arid, semi-arid and semi-humid climates coexist in the region. Mountain, Gobi, oasis, desert and other topographical features are intertwined. The northwest region in China is ecologically fragile and sensitive to climate change. It is well known that climate warming and rising temperatures accelerate the water cycle and add up the intensity and frequency of occurrence of extreme weather events such as high temperature and drought and heavy rains. At the same time, it also leads to the uneven distribution of water resources in time and space, and the complexity and difficulty of dealing with floods and droughts. On the contrary, after the temperature stops rising, the water circulation process will slow down; the water cycle elements such as precipitation, evaporation and runoff in the region will inevitably change, which will affect the industrial and agricultural production and the people’ s life in the region. In the new context of climate warming mitigation, this paper analyzes and discusses how the temperature in Northwest China has changed. Is there a warming slowdown? How does temperature respond in different seasons? In this study based on the observations of temperature by 184 meteorological stations in the northwestern region, by using K-means clustering partition, Sen’ s slope estimation and Kendall-Tau nonparametric test methods, the temperature variation characteristics of Northwest China in the past half century (1960—2015) were analyzed. The results show that the temperature in the northwestern region has been increased significantly in the past half century, and the rise rate of annual average minimum temperature is higher than those of the average annual temperature and the highest annual average temperature. From a spatial point of view, the northeastern part of the northern Xinjiang, the northern, western, central and eastern parts of Inner Mongolia, the central and western parts of Gansu Province, the northern and central parts of Qinghai Province, the central and northern parts of Ningxia Province, and the northwestern part of Shaanxi Province are the fastest warming areas. Although the temperature in the northwestern region is generally on the rise, there is a difference in specific areas. Since 1998, the temperature in the northwest region has been slowed down, and some regions have experienced a downward trend. In the past half century, the seasonal temperature and the interannual temperature in the northwestern region are not consistent, and the warming slows down in different seasons in the region. During the period from 1998 to 2015, winter is the season with the smallest increase in temperature. In most sub-regions, the warming trend in winter has been slowed down and even turned into a downward trend. This paper analyzes the trend of temperature change in the northwestern region in the past half century from different spaces and observes the phenomenon of warming mitigation in the northwest region, and this trend is inconsistent in different sub-regions and different seasons. According to the comparison with related researches, the years of warming stagnation found in this paper are consistent with the relevant research conclusions. At the same time, the conclusions of this paper could enrich the understanding of climate temporal and spatial changes in the region and provide assistance for further understanding the temperature variation law in this region.

Key words: cluster analysis')">cluster analysis, silhouette coefficient, warming mitigation, northwest China