Bunbury, J. and Gajewski, K. 2012. Temperatures of the past 2000 years inferred from lake sediments, southwest Yukon Territory, Canada. Quaternary Research 77: 355-367.
The authors write that "although the nature of the Little Ice Age is quite well known and it is recognized that the climate variations during this time occurred globally, knowledge of medieval warming is less established and there is still debate about its geographic extent."
What was done
To help shed more light on the nature of this debatable medieval warming, Bunbury and Gajewski obtained sediment cores from two lakes in the interior southwest of Canada's Yukon Territory - Jenny Lake (61.04°N, 138.36°W) and Upper Fly Lake (61.04°N, 138.09°W) - which, in their words, "yielded chironomid records that were used to provide quantitative estimates of mean July air temperature."
What was learned
The two researchers state that their chironomid-inferred temperature estimates from the two lakes "compare well with one another and also with other paleoclimate evidence from the region," noting that their data suggest "relatively warm conditions during medieval times, centered on AD 1200, followed by a cool Little Ice Age, and warming temperatures over the past 100 years." More specifically, we estimate from the graphical representations of their data that the Medieval Warm Period at both lake sites extended from about AD 1100 to 1350. And we estimate that the most recent (AD 1990) of their temperature determinations were about 0.8°C cooler than the peak warmth of the Medieval Warm Period at Jenny Lake and approximately 0.5°C cooler at Upper Fly Lake.
What it means
These results now join the many other similar results, from all around the world, which we have archived in the databases of our Medieval Warm Period Project, where it can be seen that the Medieval Warm Period was not only a global phenomenon, but that its peak warmth was very likely greater than that of the Current Warm Period: see here and here.