Leave it to the folks over at XKCD to produce a clever timeline demonstrating the Earth’s average global temperatures since the last glaciation event.  When people say, “the climate has changed before“, these are the kinds of changes they’re talking about.  The timeline is

charming, and funny, and cute… till about the year 1900.  Then, it’s just plain depressing.

 

A timeline of the Earth's temperature since the last glaciation.