e:
how...
It was spelled out in some detail in chapter 12 of David Archer's "the Long Thaw", ISBN 978-0-691-14811-3. the argument goes that the earth's orbit around the sun is almost circular at the moment, which reduces the variability in solar forcing. This last happened some 400,000 years ago when the inter-glacial lasted for 50,000 years. Climate models suggest that trigger moment for the next ice age would have been reached some three thousand years from now, and that there wouldn't have been quite enough cooling to build up enough snow cover in the northern hemisphere to let the process run away to cause another ice age. The current anthropogenic global warming will hang around long enough to make sure that the trigger level of snow cover won't be reached.
Wikipedia current artilce on Milankovitch Cycles
says much the same kind of thing, and cites an article in Science by A. Berger and M. F. Loutre dating from 2002.
-- Bill Sloman, Nijmegen