From CO2 Science
Pierce et al. (2004) dated fire-related sediment deposits in alluvial fans in central Idaho, USA, in a research program designed to reconstruct Holocene fire history in xeric ponderosa pine forests and to look for links to past climate change. Their work centered on tributary alluvial fans of the South Fork Payette (SFP) River area (~44°N, 115.6°W), where fans receive sediment from small but steep basins that are conducive to post-fire erosion. Altogether, they obtained 133 AMS 14C-derived dates from 33 stratigraphic sites in 32 different alluvial fans. The results suggested that the size and severity of large-event stand-replacing fires in this region tend to increase with temperature and that intervals of stand-replacing fires and large debris-flow events are largely coincident in SFP ponderosa pine forests "most notably during the 'Medieval Climatic Anomaly' (MCA), ~1,050-650 cal. yr BP." Based on these findings, the Medieval Warm Period was likely warmer than the Current Warm Period.
ReferencePierce, J.L., Meyer, G.A. and Jull, A.J.T. 2004. Fire-induced erosion and millennial-scale climate change in northern ponderosa pine forests. Nature 432: 87-90. (My emphasis.)
Soooo, the Medieval Warm Period was probably warmer than the current period - which is what AGW supporters keep trying to deny. How can this be? What could have caused this? Well, the one thing we can be certain of is that it wasn't caused by the activities of man.
Notice that this is from 2004. Quite a while before Stern published his hysterical report.