The Inconvenient Skeptic: The Comprehensive Guide to the Earth's Climate

by John Kehr

Antarctica, which started to cool down. 41 million years ago Antarctica was cold enough for snow and ice to form during the winter. This also coincides with the opening of the Drake Passage between Antarctica and South America. Illustration 16: Drake Passage was closed in the early Cenozoic. The opening of the passage altered the Earth's climate. Over the course of 7 million years the passage continued to open. As the passage became larger it allowed the formation of a new ocean current that is today known as the Antarctic Circumpolar Current (23) (ACC). As the ACC grew in strength, less warmth from the tropics reached Antarctica because the ACC is a current that completely surrounds Antarctica. This changing of the ocean currents resulted in the steady average cooling trend that happened from between 34 to 41 million of years ago. It is important to understand that while the average temperature of the Earth was decreasing, the average drop was caused by a large drop in temperature that was happening in Antarctica. The whole Earth was not getting cooler, Antarctica changed from what was likely a temperate place to a frigid wasteland. Illustration 17: Changing geography plays a major role in changes to the Earth's climate. (Zachos, 2008) A little over 34 million years ago the ACC became strong enough to block the warm tropical currents from reaching Antarctica, when that happened Antarctica started to form the permanent ice sheets that exist today. At the time when Antarcti...