Climate has been changing since Earth was formed. The Earth has been in an "Icy State" for about 80% of the time, while warm periods (interglacials) have been much shorter (8000 to 15000 years).
Sometimes, climate change has been abrupt, and ice age conditions have developed in just a few decades. (Older and Younger Dryas are recent examples in our Holocen period), and cooling and warming events have been shown to be of a cyclical nature, as Dansagaard-Oeschger and Heinrich events (warm and cold ones)
Actually, it looks like we have entered into the downward slope leading to a new Little Ice Age (predicted by Theodor Landscheidt, the late solar physicist) when the sun will develop what is known as the Gleissberg Double Solar Minimum (of the same importance as the Maunder Minimum of the 15th century).
This terribly cold winter and so many Mobile Polar Highs coming down from the North Pole are simply a confirmation of such predictions. Landscheidt predicted that by 2006 we'd be seeing the cold effects of the incoming Gleissberg Minimum. He was right.