Moore, J.J., Hughen, K.A., Miller, G.H. and Overpeck, J.T. 2001. Little Ice Age recorded in summer temperature reconstruction from varved sediments of Donard Lake, Baffin Island, Canada. Journal of Paleolimnology 25: 503-517.
What was done
Lake sediment cores from Donard Lake, Baffin Island, Canada (approximately 66.25°N, 62°W), were analyzed to produce a 1240-year record of average summer temperatures for this region.
What was learned
Over the entire 1240-year period from 750-1990 A.D., summer temperatures averaged
2.9°C. Anomalously warm decades with summer temperatures as high as 4°C occurred around 1000 and 1100 A.D. At the beginning of the 13th century, Donard Lake witnessed "one of the largest climatic transitions in over a millennium," as "average summer temperatures rose rapidly by nearly 2°C from 1195-1220 A.D., ending in the warmest decade in the record" with temperatures near 4.5°C.
The rapid warming of the 13th century was followed by a period of extended warmth that lasted until an abrupt cooling event occurred around 1375 A.D. The decade following 1375 A.D. was one of the coldest in the record and represented the onset of the Little Ice Age on Baffin Island, which lasted for 400 years. At the modern end of the record, a gradual warming trend occurred over the period 1800-1900 A.D., followed by a dramatic cooling event in 1900 that brought temperatures back to levels consistent with the Little Ice Age, which lasted until about 1950. Temperatures warmed during the 1950s and 1960s, whereupon they have trended toward cooler conditions to the present.
What it means
Large abrupt swings in temperature appear to be a consistent feature of climate in this region of the world, with temperatures rising and falling by as much as 2°C in as short a time period as a decade. Such natural temperature variability demonstrates the high degree of difficulty associated with attempting to separate effects of anthropogenic climatic forcing from those of natural causes.
In contradiction of politically-correct climatology, the study also demonstrates the existence of both the Medieval Warm Period and Little Ice Age on Baffin Island. And it stands in stark contrast to the climate alarmist claim that the latter part of the 20th century experienced "unprecedented" warming, at least in this part of the world, which is, however, where such anthropogenic phenomena are supposed to be most evident.