Read here. The extreme warmth and global existence of the Medieval Warming is again highlighted in the peer-research conducted in the Gulf of California's Pescadero Basin. No doubt about it: Medieval temps were hot and not just a northern Europe climate condition. (click on image to enlarge)
Researchers developed high-resolution records of diatoms and silicoflagellate assemblages spanning the past 2000 years from analyses of a sediment core extracted from Pescadero Basin in the Gulf of California (24°16.78'N, 108°11.65W). Results indicated that the relative abundance of Azpeitia nodulifera (a tropical diatom whose presence suggests the occurrence of higher sea surface temperatures), was found to be far greater during the Medieval Warm Period than at any other time over the 2000-year period studied, while during the Modern Warm Period its relative abundance was actually lower than the 2000-year mean.
More historical charts here. Other climate history postings here. Modern temperature charts.