Reference
Nyberg, J., Malmgren, B.A., Kuijpers, A. and Winter, A. 2002. A centennial-scale variability of tropical North Atlantic surface hydrography during the late Holocene. Palaeogeography, Palaeoclimatology, Palaeoecology 183: 25-41.
Description
The authors reconstructed 2000-year histories of cold-season (February-April) and warm-season (August-October) sea surface temperatures (SSTs) in the northeastern Caribbean Sea, using, in their words, "an artificial neural network and δ18O analyses of planktonic foraminifera" -- which operations were based on data obtained from sediment cores extracted south of Puerto Rico (17°53.26'N, 66°36.02'W) -- finding that "a warmer period prevailed in the NE Caribbean from AD ~700-950." Peak cold-season SSTs during this period were about 0.5°C warmer than their late 20th-century counterparts, while peak warm-season SSTs of the earlier period were about 1.0°C cooler than those of the late 20th-century. Hence, we conclude that the peak mean warmth of the MWP was about a quarter of a degree cooler than that of the most recent decade or two of the CWP.