In his seminal 1982 book Climate, History, and the Modern World, the renown climatologist Dr. H.H. Lamb revealed that sea ice in the subarctic and Arctic regions was much less
extensive during the Medieval Warm Period (9th - 13th centuries) compared to today.
JC note: TonyB et al, please let me know if you have any information / references on sea levels during the medieval warm period
But the uppermost fossils appear to be of algae that lived in the past 1000 years,
perhaps during the Medieval warm period that stretched from about AD 800 to AD 1200; the other fossils come from the past 7000 years, when it was sometimes warmer than today.
A new paper Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly (Mann et al 2009)(see here for press release) addresses this question, focusing on regional temperature
change during the Medieval Warm Period and Little Ice Age.
That assumption conflicts with studies finding that the Northern Hemisphere was warmer than present for several
decades during the Medieval Warm Period and Roman Warm Period and for thousands of years during Holocene Optimum.
Even the infamous Prof Jones at the even more infamous University of East Anglia has acknowledged in an interview with the BBC that: 1) there has been no increase in global temperature over the last decade, despite all that «dangerous» human - produced CO2; 2) global temperatures were probably
higher during the Medieval Warm Period than they are today, even though that was before all the «evil» human - produced CO2.