Forget about global warming! I was watching the Discovery channel once, a show about how glaciers shaped north America during the last ice age. They said historically the earth has an ice age approximately every 13,000 years when ocean currents for unknown reasons reverse themselves and bring frigid temperatures down from the arctic. All of modern civilization as we know it has happened during this last warming period. And the last ice age occurred approximately 13,000 years ago. Yikes!
