What was done
The authors studied the distributions of different species of siliceous microflora (diatoms), calcareous microfauna (foraminifers) and spore-pollen assemblages found in sediment cores retrieved from 21 sites on the inner shelf of the southern and eastern Laptev Sea, starting from the Lena River delta and moving seaward between about 130 and 134°E and stretching from approximately 71 to 78°N, which cores were acquired by a Russian-French Expedition during the cruise of R/V Yakov Smirnitsky in 1991.

What was learned
In the words of the five Russian researchers, this endeavor revealed "(1) the warming at the beginning of the Common Era (terminal epoch of the Roman Empire) during ~1600-1900 years BP; (2) the multiple, although low-amplitude, cooling episodes at the beginning of the Middle Ages, 1100-1600 years BP; (3) the Medieval Warm Period, ~600-1100 years BP; (4) the Little Ice Age, ~100-600 years BP, with the cooling maximum, ~150-450 years BP; and (5) the 'industrial' warming during the last 100 years."

What it means
"Judging from the increased diversity and abundance of the benthic foraminifers, the appearance of moderately thermophilic diatom species, and the presence of forest tundra (instead of tundra) pollen," Matul et al. conclude that "the Medieval warming exceeded the recent 'industrial' one," and that "the warming in the Laptev Sea during the period of ~5100-6200 years BP corresponding to the Holocene climatic optimum could be even more significant as compared with the Medieval Warm Period." Once again, therefore, we have another example of a paleoclimate study that challenges the contention of Hansen et al. (2006) that "probably the planet as a whole" is "approximately as warm now as at the Holocene maximum."

Reference
Hansen, J., Sato, M., Ruedy, R., Lo, K., Lea, D.W. and Medina-Elizade, M. 2006. Global temperature change. Proceedings of the National Academy of Sciences USA 103: 14,288-14,293.