What was done
Meteorological data from Arctic Station (69°15'N, 53°31'W) on Disko Island (West Greenland) were analyzed for the period 1991-2004, after which the data were correlated, in the words of the authors, "to the longest record available from Greenland at Ilulissat/Jakobshavn (since 1873)."

What was learned
Marked changes were noted over the course of the study period, including "increasing mean annual air temperatures on the order of 0.4°C per year and 50% decrease in sea ice cover." In addition, due to "a high correlation between mean monthly air temperatures at the two stations (1991-2004)," Hansen et al. were able to place the air temperature trend observed at Disko "in a 130 years perspective." This exercise led them to conclude that the climate changes of the last decade were "dramatic," but that "similar changes in air temperatures have occurred previous[ly] within the last 130 years." More specifically, they report that the changes they observed over the last decade "are on the same order as changes [that] occurred between 1920 and 1930."

What it means
Climate alarmists generally contend that the global warming of the past several years was unprecedented over the past one to two millennia, and that the warming of the Arctic was greatly magnified above that. However, Hansen et al.'s analysis suggests that the recent warming in West Greenland -- as dramatic as it was -- was not even unprecedented over the past century.