David Appell, “McIntyre made a bad mistake in his third article, mistaking a proxy for water mass movement for one as one for temperature.”
I believe hottie is mistaken. d15N is a proxy for nutrients whether from upwelling cold water or runoff (fertilizer sewage etc.) and the focus of the Rahmsdorf paper was using Mann’s temperature reconstructions to estimate AMOC. So d15N as used by Rahmsdorf would have to be a temperature proxy for that location and not a generic nutrient proxy. Over fishing in that region would reduce nutrients, fish do poop rather regularly, fewer fish less fish poop.. Rahmsdorf is ignoring confounding factors and assuming higher nutrients means increase cold water flow but there are temperature reconstructions for the region better suited for that purpose.
So Rahmsdorf has treemometers with precipitation and nutrients as confounding factors, varves with land use as a confounding factor and dN15 with precipitation/land use (runoff) and over fishing as confounding factors. Then to boot, the d15N reconstruction has only 4 data points prior to 1930 and only one prior to 1700 which is ridiculous for Rahmsdorf’s analysis.