Recent air-temperature changes in the Arctic

A detailed analysis of the spatial and temporal changes in mean seasonal and annual surface air temperature (SAT) in the Arctic is presented mainly for the period 1951-2005. Mean seasonal and annual homogenized and complete series of SAT from up to 35 Arctic stations were used in the analysis. The focus in this paper is on the 11 years 1995-2005, a period which saw dramatic warming in the Arctic (> 1 degrees C for annual values in relation to the 1951-90 mean). An abrupt rise in SAT occurred in the mid-1990s and was most pronounced in autumn and winter (> 2 degrees C). The greatest warming in the period 1995-2005 occurred in the Pacific and Canadian regions (> 1 degrees C), while the lowest was in the Siberian region (0.82 degrees C). This period has been the warmest since at least the 17th century. In particular, 2005 was an exceptionally warm year (> 2 degrees C in relation to the 1951-90 mean) and was warmer than 1938, the warmest year in the 20th century. The seasonal and annual trends of the areally averaged Arctic SAT for the periods 1936-2005, 1951-2005 and 1976-2005 are positive, with the exception of winter and autumn for the first period. The majority of trends calculated for the last two periods are statistically significant. While there are varying opinions about the forces driving the present warming, it seems likely that the marked rise in SAT in the mid-1990s (mainly from 1994 to 1995) was caused by (i) a set of natural factors, (ii) non-linear effects of greenhouse-gas loading, or (iii) the combined effect of these two groups of factors.