Read here. Peer reviewed research of oyster remains in Hudson River estuary continues to add to the overwhelming evidence that Roman and Medieval warmings exceeded modern temperatures.
"The authors located fossil oyster beds within the area of the Hudson River estuary....Results of their analyses indicated that "oysters flourished during the mid-Holocene warm period," when "summertime temperatures were 2-4°C warmer than today." Thereafter, the oysters "disappeared with the onset of cooler climate at 4,000-5,000 cal. years BP," but "returned during warmer conditions of the late Holocene," which they specifically identified as the Roman and Medieval Warm Periods....They further report that their shell dates suggest a final "major demise at ~500-900 years BP," which timing they describe as being "consistent with the onset of the Little Ice Age." Because the oyster beds of Tappan Zee have not been reestablished during the Current Warm Period, we conclude that temperatures in this region today are not as warm as they were during the MWP (~ AD 600-1250)."