I just found this story interesting. Paleontologist Paul Sereno was searching for dinosaur bones in the Sahara Desert eight years ago (he found tons) when he stumbled on some human bones, along with traces of pottery, stone tools and what were obviously burial sites. It took some years to organize expeditions to go back and dig, but eventually they found about 200 graves belonging to two different successive populations.
A group that's been named the Kiffian culture lived there from 9,700 to 8,200 years ago when it was the shore of a large, shallow freshwater lake, where they speared fish and hunted gazelles. Then came a thousand years of extreme dryness, then the lake and vegetation returned, and the site was inhabited by smaller, finer-boned people called the Tenerians.
If you want more info, check out the National Geographic Society, which helped to fund the expeditions (and here's a photo gallery), or a scientific paper here.
This, of course, is an extreme example of the fact that climate change is hardly new. About 100 million years ago the area was forested and inhabited by dinosars and crocodiles, and evidence of people living there about 50,000 years ago has been found. The lakes dried up during the Ice Age, then returned about 12,000 years ago.
I'm a mild skeptic on human-caused climate change, but aware that I haven't studied enough to be cocksure in my opinion. I do note that for committed Goreians it's more like a religion than science.