Fairbanks Daily News-Miner: Twenty thousand years ago, it was so cold in North America — and had been for so long — that much of the continent was covered by ice two miles thick. A hundred and five thousand years before that, it was so warm that giant ice caps melted and the oceans rose 15 feet above their current levels. The climate has been changing on its own since long before coal-fired power plants and SUVs. In the last 150,000 years, the Earth as a whole has been a few degrees warmer than it is …