Long-term trends in Arctic surface temperature and potential causality over the last 100 years

The rate of warming of the Arctic surface temperature has exceeded that of the global surface temperature in recent decades. However, the underlying process and causes of the long-term warming remain uncertain. In this paper, we explored the factors underlying variation in Arctic mean surface temperature anomalies (AMTA) using a piecewise linear model for 1920–2018. This analysis indicated that the change in AMTA during the study period could be divided into three segments, with AMTA increasing from 1920 to 1938, declining from 1939 to 1976, and finally increasing rapidly after 1977. By a newly developed rigorous formalism of information flow, we found a one-way causality from the driving forces to AMTA. Moreover, the AMTA evolution could mainly be attributed to a combined effect of anthropogenic and natural factors (e.g., CO 2, aerosol, and PDO). During the first warming stage (1920–1938), the PDO and aerosols are the main factors determining the change in AMTA. During the second warming stage (1977–2018), greenhouse gases, dominated by CO 2 , are the major factors accounting for the Arctic warming. In 1939–1976, the observed cooling may be associated with aerosols, clouds, and land use. A better understanding of the driving mechanism underlying AMTA evolution provides insight into the historical Arctic climate change, and can improve the prediction of future changes in AMTA.