Read here. Research scientists find more evidence that Medieval Warming produced temperatures in excess of modern period temperatures. Switzerland isotope data from a lake's sediment core provides proof.
"For some time now the climate alarmists have been claiming that temperatures during the latter part of the 20th century were the warmest of the past thousand years. According to the authors of this paper, however, that claim is false....And citing Bond et al. (1997), they note that the MWP and LIA are just the most recent manifestations of "a pervasive millennial-scale coupled atmosphere-ocean climate oscillation" that has absolutely nothing to do with variations in the air's CO2 content."