Am confused! Env change and archaeology...comes up as an available pdf download, not in Nature but in Palaeogeography, Paleoclimatology, Paleoclimatology
http://www.uni-koeln.de/sfb389/sonstiges/kroepelin/255%202001%20Palaeo3%20169%20WNPL.pdf
The link you give is for another article in Nature; I should be able to get this for you but do you def want it?
It's Timing of the Younger Dryas event in East Africa from lake-level changes