Background
The authors write that "predicting the response of the Greenland Ice Sheet to future climate change presents a major challenge to climate science," but they say that "paleoclimate data from Greenland can provide empirical constraints on past cryospheric responses to climate change, complementing insights from contemporary observations and from modeling."

What was done
As they describe it, Axford et al. "present Holocene climate reconstructions from five lakes along the western Greenland Ice Sheet margin, near Jakobshavn Isbrae and Disko Bugt," where "insect (chironomid) remains from North Lake are used to generate quantitative estimates of summer temperatures," and where "changes in sediment composition at the five study lakes are interpreted as evidence for ice sheet fluctuations, changes in lake productivity, and regional climate changes throughout the Holocene."

What was learned
The six scientists report that "temperature reconstructions from subfossil insect (chironomid) assemblages suggest that summer temperatures were warmer than present by at least 7.1 ka (thousands of years before present), and that the warmest millennia of the Holocene occurred in the study area between 6 and 4 ka." They also note, in this regard, that "previous studies in the Jakobshavn region have found that the local Greenland Ice Sheet margin was most retracted behind its present position between 6 and 5 ka," and they say that they used chironomids to estimate that "local summer temperatures were 2-3°C warmer than present during that time of minimum ice sheet extent [italics added]," while indicating that the Little Ice Age "culminated at North Lake with 19th century summer temperatures that were colder than any other period in the record since deglaciation [italics added]."

What it means
Against this backdrop of data-based information, it should be clear to everyone that there is nothing unusual, unnatural or unprecedented about current temperatures along the western Greenland Ice Sheet margin - or anywhere else on the planet, for that matter - for temperatures there currently fall well within the extreme bounds experienced over the course of the Holocene. And it should also be realized that starting from the coldest point of the entire Holocene (the depths of the Little Ice Age), one could well expect that once started, warming (for whatever reason) could well be anticipated to be substantial.