evidence: So, could we one day see the abrupt climate change depicted in "The Day After Tomorrow"? Or can we expect a more gradual transition to a "mini Ice Age" as some have speculated? [...] To look into our climate future, we need to review the past. An Ice Age is a "glacial period" in which the Earth’s surface and atmosphere cools by over 5°C, causing the polar ice caps and glaciers to expand. Brought on by naturally-occurring shifts in the Earth’s orbit and tilt, which change where solar energy hits Earth’s surface, these periods occur fairly regularly and can last tens of thousands of years. [...] For those who look to the possibility of an impending Little Ice Age to counterbalance the impacts of human-induced climate change, the scientists say, be careful what you wish for.