Due to the formation of the Antarctic Circumpolar Current, enabled by plate tectonics, Antarctica became thermally isolated from the rest of the earth initiating 1) a permanent ice cap, 2) extensive sea ice that extruded cold brine that filled the ocean’s bottom water, and 3) Intensified upwelling that increased productivity that drew down atmospheric CO2 to current levels.

As a result of increasing cold Antarctic Bottom Water, oceans ventilated its its displaced ancient bottom water heat. As a result of a 50 million year cooling trend, the earth is now locked into a fluctuating balance between cold ice ages and warm interglacials

Jim Steele is Director emeritus of San Francisco State University’s Sierra Nevada Field Campus, authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism, and proud member of the CO2 Coalition.