According to a new report prepared by a team of international scientists, deep-sea remains of ancient corals could be used to understand carbon dioxide in the oceans, both past and present. The report, published in the journal Nature Geoscience, uses coral fossils as a sort of time machine to investigate the rise of carbon dioxide and its role in ending the last ice age. The researchers extracted fossilized coral remains deposited about 15,000 years ago during the last ice age.