The publication is the first major synthesis of assessments of climate changes occurring in the Arctic, which were obtained in AARI on the basis of the most complete array of historical data on the state of the atmosphere, sea ice and ocean for most of the XX century. and new data. At the same time, assessments of the variability of the Arctic climate characteristics are accompanied by an analysis of the causes and the determination of the possible contribution of natural and anthropogenic factors. In particular , The contribution of aerosol pollution and small gas impurities to the formation of the vertical temperature distribution in the Arctic atmosphere is analyzed ,. contribution of atmospheric circulation fluctuations to air temperature variability, The role of water exchange between the Arctic basin and the North Atlantic in shaping the impact of the Arctic on the climate