evidence: The big ice ages account for roughly 25 percent of the past billions of years on Earth, says Sandstrom. The most recent of Earth’s five major ice ages in the paleo record dates back 2.7 million years and continues today. Within these large periods are smaller ice ages called glacials and warm periods called interglacials. [...] At a Glance - There have been five big ice ages in Earth's 4.5-billion-year lifespan and scientists say we're due for another one.