Paper Reviewed
Vilanova, I., Schittek, K., Geilenkirchen, M., Schabitz, F. and Schulz, W. 2015. Last millennial environmental reconstruction based on a multi-proxy record from Laguna Nassau, Western Pampas, Argentina. Neues Jahrbuch für Geologie und Palãontologie 277: 209-224.

Vilanova et al. (2015) developed a multi-proxy millennial environmental record from sediment cores extracted from Laguna Nassau, a shallow lake that apparently developed within a blowout depression in the semi-arid sandy lowlands of the Western Pampas of Argentina. And as they go on to report, "this multi-proxy stacked record reveals the evolution of an incipient water body subjected to warm and dry conditions from ~900 to 770 cal yr BP, an interval that is coeval with the Medieval Climatic Anomaly," which is also more commonly known as the Medieval Warm Period or MWP.

Continuing, the five researchers write that the buried remains of the highest percentages of Celtis -- commonly known as hackberries or nettle trees, which represent a genus of about 60-70 species of deciduous trees widespread in warm temperate regions -- in the Laguna Nassau pollen record suggest the existence of "a semi-arid climate and indicate that [drum roll] drier and warmer conditions than today predominated in the area from about 900 to at least 770 cal yr BP."

And so we have yet another well-documented example of the pure and simple fact that the much-studied Medieval Warm Period likely was somewhat warmer than the Current Warm Period has been to date, and during a time when the atmosphere's CO2 concentration was only about 280 ppm, compared to the approximate 400 ppm of today. And these facts further suggest that the historical increase in the air's CO2 content that began with the Industrial Revolution may have had nothing at all to do with the development of the Current Warm Period, which still has a substantial way to go before it reaches the degree of warmth that characterized the peak warmth of the MWP.