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To: longnshort who wrote (911)	9/5/2011 12:38:13 PM
From: Bread Upon The Water	Read Replies (3) \| Respond to of 85487

But this was good for the polar bears, no? What is needed, for our current situation, is data going the other way showing that it rapidly warmed also and did away with the sea ice polar bears depend on.

To: longnshort who wrote (911)	9/6/2011 9:14:17 PM
From: Brian Sullivan	Read Replies (1) \| Respond to of 85487

Cold, stormy conditions caused by an abrupt shift in atmospheric circulation froze the continent almost instantly during the Younger Dryas less than 13,000 years ago The Fantastic Mystery of the Younger Dryas The third and most recent theory is that some kind of enormous extraterrestrial but near earth explosion happened ... like a swarm of comets hitting the atmosphere all at once and exploding, maybe even running into the earth but not leaving much of a crater. This theory gets pretty zany. In one region of North America, researchers claim that there are little tiny bits of shrapnel in almost every large extinct mammal bones that they find. In other words, the North American megafauna got wiped out in a matter of seconds or minutes because they literally got fragged. This event would have also involved climate change of the type we see with the Younger Dryas, and the timing of the event is quite possibly perfect for explaining the onset of the Younger Dryas glaciation. The latest study is from Science, and is a follow up on criticism leveled at an earlier paper published in PNAS. *From the Science* paper:** We report abundant nanodiamonds in sediments dating to 12.9 ... thousand calendar years before the present at multiple locations across North America. [there are two types of ] diamond ... in this boundary layer but not above or below that interval. Cubic diamonds form under high temperature-pressure regimes, and n-diamonds also require extraordinary conditions, well outside the range of Earth's typical surficial processes but common to cosmic impacts. .... These diamonds provide strong evidence for Earth's collision with a rare swarm of carbonaceous chondrites or comets at the onset of the Younger Dryas cool interval, producing multiple airbursts and possible surface impacts, with severe repercussions for plants, animals, and humans in North America. This study is reviewed in a recent blog post at Real Climate I venture to guess that this impact theory will pan out and be demonstrated as very likely. All of this must be understood in the context of Milankovitch Cycles, of course. These are the orbital cycles that more or less (more more than less, as a matter of fact) map onto the comings and goings of ice ages over the last two million years. Within the context of these orbital geometric cycles, events such as running into a herd of comets or great fresh water inland seas catastrophically dumping into the ocean or sudden metastable changes in air currents could turn on, or off, a particular climate pattern.