Bloomberg: Carbon dioxide in the earth’s atmosphere has risen to its highest level in at least 2.1 million years, according to a new investigation of the greenhouse gas’s role in ice ages over the millennia. Researchers including Columbia University’s Baerbel Hoenisch drilled into the ocean floor off the coast of Africa to remove shells of ancient marine animals called foraminifera that contain climate records, according to the study published today on Science’s Web site. Previous evidence of …