What was done
Combining early observational records from 13 locations along the southern and western coasts of Greenland, the authors extended the overall temperature history of the region - which stretches from approximately 60 to 73°N latitude - all the way back to AD 1784, adding temperatures for 74 complete winters and 52 complete summers to what was previously available to the public.

What was learned
In the words of the authors, "two distinct cold periods, following the 1809 'unidentified' volcanic eruption and the eruption of Tambora in 1815, [made] the 1810s the coldest decade on record." The warmest period, however, was not the last quarter century, when climate alarmists claim the earth experienced a warming that was unprecedented over the past two millennia. Rather, as Vinther et al. report, "the warmest year in the extended Greenland temperature record [was] 1941, while the 1930s and 1940s [were] the warmest decades." In fact, their newly-lengthened record reveals there has been no net warming of the region over the last 75 years!

What it means
With approximately half the study region located above the Arctic Circle (where CO2-induced global warming is suggested by climate models to be most evident and earliest expressed), one would expect to see southwestern coastal Greenland's air temperature responding vigorously to the 75-ppm increase in the atmosphere's CO2 concentration that has occurred since 1930, even if the models were only half-way correct. However, there has been no net change in air temperature there in response to the 25% increase in the air's CO2 content experienced over that period. And this is the region the world's climate alarmists refer to as a climatological canary in a coal mine??? If it is, real-world data suggest that the greenhouse effect of CO2 has been hugely overestimated.