I'm debating with a global warming skeptic, and I'm pretty new at this. He's pulled this graph showing the temperature from the last 2000 years and said that temperatures have previously risen faster and by greater numbers than the current anthropogenic warming. I'm not sure if this claim is true, so I was hoping someone could help me with this. I was wondering if someone could also tell me if climate scientists usually use data sets from the Southern Hemisphere. I read that scientists use the North Hemisphere mean because there are larger sets of proxy data there (such as tree rings etc). Something doesn't quite feel right about the website.