The Medieval Warm Period in Antarctica: How two one-data-point studies missed the target

Guest essay by Sebastian Lüning

A common claim by warmists in the climate debate is the alleged absence of the Medieval Warm Period (MWP) in the Southern Hemisphere. In a previous post we discussed the MWP in Australia, New Zealand and Oceania. In the following, we will take a look at Antarctica.

In 2012 a group led by Robert Mulvaney of the British Antarctic Survey published in Nature an ice-core record of deuterium variations from James Ross Island, off the northeastern tip of the Antarctic Peninsula, in which deuterium was used as a temperature proxy. Whilst they found indeed a slight warming centred around 1000 AD, later developments are puzzling. Unexpectedly, the highest temperatures of the past millennium occurred during the Little Ice Age (LIA) around 1750 AD (Fig. 1). And the coldest temperatures were found at 1400 AD, during the late MWP. Based on this apparent mismatch with the…