10,000 years ago is but a moment ago on Sagan's cosmic clock. The real key to the story is that we "recently" came out of an ice age and who is to say that the coming out is finished? They have unknowingly admitted to a natural warming cycle in publishing this scare story. I'd be more worried about when that giant ice sheet that extended all the way down to Long Island Sound was going to return.
And latest NIE notwithstanding, Nuclear Winter will cure Global Warming long before the temp has gone up more than a degree to two.