Kind of hard to have palaeo climate discussions here. Also hard to figure out where to start the thread with a new hypothesis, about what caused the extinction of the Mammoths. Biology? Theory development? or Earth. Since there is a lot of Earth changes going on I choose for the latter. BTW the answer to the question is the Clathrate gun (Kennett et al). My guess is that the Clathrate gun did more than causing Tsunamis, it created a dramatic precipitation increase, possibly world wide, that destroyed the arid Mammoth steppe, the essential biotope for the Megafauna.