Read here. The IPCC climate science political agenda was to eliminate the Medieval Warming Period, which was confirmed by the recently exposed Climategate activities. Not only does non-fraudulent climate science show decisively that there was a Medieval Warming but that it also very much existed in the western hemisphere, as this study indicates.
The percentage of diatoms found within a sediment core is a proxy for sea surface temperatures. This proxy indicates much higher temperatures during the Medieval Warming. (click on image to enlarge)