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The exceptional warming of the polar regions from 1919 to 1939

        Abstract to the 1999-artcile: “Changes in atmospheric circulation over northern hemisphere oceans associated with the rapid warming of the 1920s”, by Fu Congbin et al. *)


      (Excerpt) Global mean surface temperature has increased since the late 19th century. The warming occurred largely during two periods: 1920 1940, and since the mid-1970s. Although most recent studies have focused on the latter period, it is of interest to analyse the earlier period and compare its major features to the recent warming episode. The warming during 1920-1940 occurred most rapidly during the 1920s. It was strongest at high northern latitudes in winter, a pattern now believed to be characteristic of' greenhouse warming'. This warming of the Arctic was much discussed during the 1930s and 1940s, but the data available at that time were mostly derived from land areas. In this paper, we use the COADS marine data set and recent compilations of land surface temperature data sets to examine the behaviour of the surface fields over the ocean during this event. Considering the thermal and atmospheric fields at the surface, the strongest signal occurs in the North Atlantic Ocean during winter, being distinct but more gradual in the other oceans and seasons. The Northern Hemisphere continental record shows that both middle and high latitudes experienced rapid warming in the early 20th century warming interval (the 1920s and 1930s, hereafter referred to as ETCW). Temperature data for northern tropics, while displaying similar general characteristics, exhibit some differences with regard to timing and rates of change. There is a suggestion of weakening of the westerlies and the trade wind system in the 1930s, following an intensification of the westerlies across the North Atlantic during the previous two decades (continues).

*) Congbin, Diaz, Dongfeng & Fltecher  (1999);  International journal of climatology , vVol. 19, pp. 581-606.


Chapter 5_12

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