Considering we are overdue for another ice age, the huge increase in CO2 in our atmosphere
just might save us from the fate. Imagine the entire norther hemisphere smothered in ice. Famine
would be rather immediate.
How Often Do Ice Ages Happen?
So, how often do ice ages happen, and when is the next freeze expected to begin?
The answer to the first question depends on whether you're talking about big ice ages or the little ice ages that happen within those larger periods. Earth has undergone five big ice ages, some of which lasted for hundreds of millions of years. In fact, Earth is in a big ice age now, which explains why the planet has polar ice caps. [Photo Gallery: Antarctica's Pine Island Glacier Cracks]
Big ice ages account for about 25 percent of Earth's past billion years, said Michael Sandstrom, a doctoral student in paleoclimate at Columbia University in New York City.
The five major ice ages in the paleo record include the Huronian glaciation (2.4 billion to 2.1 billion years ago), the Cryogenian glaciation (720 million to 635 million years ago), the Andean-Saharan glaciation (450 million to 420 million years ago), the Late Paleozoic ice age (335 million to 260 million years ago) and the Quaternary glaciation (2.7 million years ago to present).
These large ice ages can have smaller ice ages (called glacials) and warmer periods (called interglacials) within them. During the beginning of the Quaternary glaciation, from about 2.7 million to 1 million years ago, these cold glacial periods occurred every 41,000 years. However, during the last 800,000 years, huge glacial sheets have appeared less frequently — about every 100,000 years, Sandstrom said.
This is how the 100,000-year cycle works: Ice sheets grow for about 90,000 years and then take about 10,000 years to collapse during warmer periods. Then, the process repeats itself.itself.
Given that the last ice age ended about 11,700 years ago, isn't it time for Earth to get icy again?
"We should be heading into another ice age right now," Sandstrom told Live Science. But two factors related to Earth's orbit that influence the formation of glacials and interglacials are off. "That, coupled with the fact that we pump so much carbon dioxide into the atmosphere [means] we're probably not going to enter a glacial for at least 100,000 years," he said.
How Often Do Ice Ages Happen?