“...and on our way back down into the freezer again.”
Looking at the past interglacial warm periods - our current period is a bit on the long side, so I would not be surprised if we are not due for a REAL, mile-thick ice over Seattle, Ice Age.
Some scientists think that these ice-age periods can kick-off in a matter of years-decades, not the hundreds to thousands of years one might think. (I have read other papers that talk about rapid cooling on the order of weeks to months as well - but not sure how much the data backs up their ideas).
http://www.universetoday.com/83906/younger-dryas/
http://www.esd.ornl.gov/projects/qen/nerc130k.html
It is believed currently that a comet hit the residual ice sheat in Canada. The broken pieces then clogged the Gulf of St. Lawrence, and the massive fresh water runoff into the Atlantic actually brought the North Atlantic thermohaline circulation to a halt. Europe instantly returned to Ice Age glacial conditions.