This provides links to a lot of good information on climate change.
An important Russian scientist recently predicted a new little ice age, based on the current trend of fewer sunspots than normal. Link: New little ice age? He believes the sun varies in energy output, and that is the principal driver of climate change. Take a look at the latest official sunspot numbers: Link: Recent sunspot counts. Except for a peak above average in 2011, it’s been going on for nearly two years. Of course, all this is controversial. But while climate change is reality, and always has been, we may have global cooling rather than warming, and the changes may not be mankind’s fault.
The Maunder Minimum is thought to have caused the Little Ice Age. Link: The Maunder minimum.
Historically, the climate in the last 12,000 years has been all over the place. However, it’s easier to find data on the past 4,500 years, and there is plenty of variation in that time frame. Harris-Mann is a good website, though biased toward the existence of a coming man-made catastrophe. The chart they provide is excellent to understand what’s been happening: Link:Harris-Mann, last 4500 years.
Steve Goddard’s excellent website counters the catastrophe fears somewhat: Steve Goddard's blog -- Climate Skeptic.
For a really good explanation of what goes into Earth’s climate, see Link: A terrific summary of climate change.
Climate change is a political football right now. Climate is always changing. The real question is whether it is caused by man and his carbon dioxide emissions. There are plenty of logical arguments that it isn’t.