Causes of the northern high-latitude land surface winter climate change

In the past two decades, the northern high-latitude (>40°N, NHL) land surface winter climate has experienced some of the most rapid changes on Earth, warming at almost 2.5 times the global average warming. Here we examine impacts of two dominant climate modes - Arctic Oscillation (AO) and Aleutian Low (AL) - on the winter NHL land surface temperature for the period 1958-2004, showing that 1) a combination of the AO and AL explains 70% of the variance of the NHL land surface temperature variability, including the cooling during the 1960s and 1970s and the persistent warming thereafter; and 2) interactions between the AO and AL tend to constrain impacts of the extremes of the AO and AL and minimize spatiotemporal extremes in the NHL climate. The amplification of the winter NHL land surface warming relative to the global average warming can be attributed to the combination of the AO and AL, although the extent to which the greenhouse warming may influence the AO and AL is uncertain.