"The Arctic wasn't always frozen tundra. About 3.6 million years ago, the far north was blanketed in boreal forests, and summers were 8 degrees Celsius warmer than they are today, geologists report May 9 in Science." http://www.sciencenews.org/view/generic/id/350292/description/The_Arctic_was_once_warme... or colder the Earth is a very special planet that tolerates all sorts of variations in climate. Past CO2 levels have been at the 3,000 ppm level and we evolved. Tell Al Gore.