The Arctic 1920–40 warming is one of the most puzzling climate anomalies of the twentieth century. Over some 15 yr the Arctic warmed by 1.78C and remained warm for more than a decade. This is a warming in the region comparable in magnitude to what is to be expected as a consequence of anthropogenic climate change in the next several decades. A gradual cooling commenced in the late 1940s bringing the temperature back to much lower values, although not as cold as before the warming started. …this warming was associated with and presumably initiated by a major increase in the westerly to southwesterly wind north of Norway leading to enhanced atmospheric and ocean heat transport from the comparatively warm North Atlantic Current through the passage between northern Norway and Spitsbergen into the Barents Sea….the increased winds were not related to the NAO, which in fact weakened during the 1920s and remained weak for the whole period of the warm Arctic anomaly. …the process behind the warming was most likely reduced sea ice cover, mainly in the Barents Sea. This is not an unexpected finding because of the climatic effect of sea ice in comparison with that of an open sea but is intriguing since previously available sea ice data (Chapman and Walsh 1993) did not indicate a reduced sea ice cover in the 1930s and 1940s. However, as we have shown here recent sea ice datasets [Johannessen et al. (2004) give a detailed presentation] actually showed a retreat in this period.

http://www.nerc-essc.ac.uk/~olb/PAPERS/len19.pdf

This 1932 article demonstrates that, unlike the modern era, the warming affected both poles whilst highlighting the continued retreat of the glaciers generally and in Greenland and Alaska specifically:

“Some great world change is taking place on the Antarctic Continent. Its glaciers are shrinking. L.A. Bernacchi, who visited the South Polar land 30 years ago, says that the Great Ice Barrier which fronts the continent with a wall of ice for 250 miles has receded at least 30 miles since it was first seen and surveyed. Sir James Ross…on the earliest Antarctic expedition of the nineteenth century, and those who followed him, left clear descriptions of this tremendous ice frontage and its position. It was a cliff 150ft. high and 1000ft. thick. But now it appears to be continuing its century-long process of shrinking; and that process may have been going on for centuries. It might imply, unless it is offset by some increase of ice in another less explored part of the Antarctic, that the climate of the South Pole is changing and becoming warmer. The shrinkage of the Alpine glaciers of Europe is a well-known and carefully measured fact. Professor Buchanan, of. Edinburgh, drew attention to it twenty years ago, and showed from old and accurate drawings of (many) that they were retreating rapidly. This led to the continuous measurement of the Swiss glaciers (and) examination of other glaciers of the Northern Hemisphere, Greenland, Alaska, and elsewhere. Prom these measurements many geologists concluded that the northern part of the globe was still recovering from the last of its Ice Ages, of which the more southerly of its glaciers in Europe were a relic. If all the glaciers of the Southern Hemisphere as well as those of the Northern are shrinking, the geologists would have a new problem to examine. It would be whether, instead of areas of cold and ice having shifted on the earth, the whole globe is growing warmer. Even if that could be shown the change might prove to be temporary.” [link]

“All series show warm periods in the 1940s and 1990s, and a cold period in the 1960s. Salekard (the only station with observations at that time) was cold also around 1900.”

Page 40 summary and conclusions:

1. Increasing temperatures from 1900 to the mid-1940s (often referred to as the “early 20th century warming”).
2. Decreasing temperatures from the mid-1940s until about the mid-1960s.
3. A “recent warming” from the 1960s to 2003.
4. For Yamal this is shifted to the period 1965/70s-1990/95s.”

DOI: 10.1111/j.1600-0870.2004.00060.x

“The global gridded SAT data set (Jones et al., 1999) used most extensively for studies of climate variability has major gaps in the northern high latitudes, in particular over the ice-covered Arctic Ocean and some surrounding land areas.”

”However, it remains open to debate whether the warming in recent decades is an enhanced greenhouse-warming signal or natural decadal and multidecadal variability (Polyakov and Johnson, 2000; Polyakov et al., 2002), e.g. as possibly expressed by the arctic warming observed in the 1920s and 1930s followed by cooling until the 1960s (e.g. Kelly et al., 1982).”