(click on above for original/source)
What do boreholes, varves, birds, diatoms, tree-rings, sediments, pollen and ice have common?
Each has been used in a unique peer reviewed study confirming that the Arctic polar regions during the Medieval Warming Period (MWP) were warmer than the modern era.
That's 15 scientific studies, using actual empirical evidence, confirming the known facts and historical anecdotal evidence.
Note: map source