Thirty-eight million years ago, tropical jungles thrived in what are now the cornfields of the American Midwest and furry marsupials wandered temperate forests in what is now the frozen Antarctic. A debate has long been raging in the scientific community on what changes in our global climate system led to such a major shift from the more tropical, greenhouse climate of the Eocene to the modern and much cooler climates of today. Researchers have now found some of the strongest evidence to date that the Antarctic Circumpolar Current (ACC) played a key role in the major shift in the global climate that began approximately 38 million years ago....