Abrupt climate changes

In response to my last post in which I detailed the high uncertainty  both chronologically and geographically of climate data: I came across a recent article by D’Andrea et al. (2011) which presents a record of temperature changes in Greenland. The climate history of Greenland was reconstructed from lake sediments in Kangerlussuaq, close to the Western Settlement. 

As the lake is so close to the original Viking settlement it more accurately indicates the air temperatures the Inuit/Dorset/Norse people would have experienced. This is a much needed improvement from temperatures reconstructed from ice cores from the Greenland ice sheet which is situated miles away. Furthermore, it was shown that ice-free regions have more temperature variability than the Greenland ice sheet. Thus the ice sheet isn't accurate enough to infer climate forces on the Norse society.

D'Andrea et al., (2011) found the Norse did colonise Greenland during a warm spell (figure 2.)  In addition, it was also discovered that the Norse Society collapsed just after a particularly cold period. This change in temperature was very abrupt (4^oC in approx. 80 years). This puts into perspective the increase of 0.8^oC over the last 150 years. D'Andrea et al., (2011) stresses that it is the magnitude rather than the rate of change that matters. This rapid and large decrease in temperatures must have greatly increased the vulnerability of the Vikings living in Norse Greenland. 

Figure 2. 

This article showed temperature changes at a fine decadal resolution. However, I think that when technology permitting a much finer - yearly record of temperature changes is needed. This is because the Norse were resilient enough to withstand one or two years of harsher climates as long as milder climates followed. If it was that there were decades which were solidly cold then climate change must have been the key factor that pushed this society over the edge. Although this raises the question as to how the Norse survived such cold conditions for so long and have collapsed? On the other hand, if there were periods of slightly warmer conditions, it begs the question as to why these failed to save them?