Regardless of what you think of man-made climate change, I'm pretty sure that the general idea behind global warming leading to global cooling is sound and has been documented as having had happened in the past (I think this same basic mechanism caused one of the ice ages or perhaps the mini-ice age of either the 1600s or the 1800s?).
And before I begin, no, I don't have any sources, but again, I think this is sound regardless of whether you believe in man-made change or not.
Okay, so initially warming leads to melting polar ice caps, glaciers in Greenland and Antarctica, and elsewhere. This influx of cold water shuts down the global conveyor belt of hot and cold water (of which the Gulf Stream is only a part). Since parts of the northern hemisphere, particularly northern Europe, are warm primarily because of the Gulf Stream, this leads to cooling in those areas. If you look at a map, for example, England is much farther north than, say, Wisconsin, where I live, yet temperatures in winter seldom drop below freezing in England in this day and age. Wisconsin, on the other hand, can get pretty f-ing cold.
Here's where things get a little murkier. From my understanding (again, I'm not a scientist) there are some who think that the global warming at this point would be intense enough that not much of this would really make a difference. Others think the following:
As the temperatures drop in the northern hemisphere and around Europe, glaciation rebounds and we continue with colder, not warmer, temps in the northern latitudes.
Some may even take this a step further. As glaciation increases, more sunlight is reflected off the massive amounts of snow and ice, and less is absorbed into the atmosphere. Ultimately, this drops temperatures worldwide.
Again, putting the "man-made" part of climate change aside, I think the rest of that scenario is pretty sound science.
Some of that I got from a geology class in college, some from another science class in college, and some from the book "A Brief History of Nearly Everything," by Bill Bryson.
I suppose from this point of view a person could argue that global warming is actually a good thing if it staves off another full-blown ice age.
Oh, and The Day After Tomorrow was a movie, and yes, it was a bad one (so I heard). I doubt you'll find any man-made global warming proponents who would classify it as factually (hypothetically) accurate.
(sorry this is so long...I don't normally write this much...)
BL2-
I understand what you're saying about Lincoln. I'm wondering if it's crossed your mind that perhaps terrorist attacks are not equivalent to the government being overthrown. And really, I won't venture as far as to say they are or aren't, but have you thought about that? I will say that you're correct -- Bush will be judged by historians in the future. It is possible that history will forgive him; it's also possible, and personally I think more likely, that history won't rate him alongside Lincoln.
Just some perspective -- you're right that we don't know, but you don't know either.