As so many past studies have documented, the Medieval Warming Period was indeed hotter than our current climate, especially in the extreme north and polar regions, such as Greenland and Iceland. The empirical evidence from past research, using a wide variety of scientific techniques, confirms the anecdotal information that was written in the historical past. A newly published study again confirms both the past scientific efforts and historical writings.
Ran et al. performed a diatom-based reconstruction of sea surface temperatures from waters of northern Iceland. Their analysis found that temperatures were approximately 0.6°C higher during the AD 940-1300 period versus modern temperatures. In addition, a strong solar radiation influence was noted in the data. (click on image to enlarge)
"Ran et al. reconstructed summer sea surface temperature (SST) on the North Icelandic shelf for the period AD 940-2006, based on their high-resolution and precisely dated diatom records, along with the help of "a modern diatom-environmental dataset from around Iceland...In the words of the four researchers, their diatom-based SST record indicates that the sea surface on the North Icelandic shelf "was not as warm during the last century as during the Medieval Warm Period (MWP)." More specifically, they write that "warm and stable conditions with relatively strong influence of the Irminger Current on the North Icelandic shelf are indicated during the interval AD 940-1300, corresponding in time to the MWP," and that "a considerable cooling at ~AD 1300 indicates the transition to the Little Ice Age (LIA) with increased influence of Polar and Arctic water masses deriving from the East Greenland and East Icelandic currents."...they end by stating that "the data suggest that solar radiation may be one of the important forcing mechanisms behind the palaeoceanographic changes."" [Lihua Ran, Hui Jiang, Karen Luise Knudsen and Jón Eiríksson 2011: Palaeogeography, Palaeoclimatology, Palaeoecology]