 Welcome to week four of Denial 101X. Last week we looked at the many human fingerprints indicating that humans are causing global warming. This week is divided into two, the past and the future. We can't run lab experiments with our whole climate system, but what we can do is look at past climate change throughout Earth's history. How our climate behaved in the past provides insights into how our climate will behave in the future. Peter Jacobs takes us into the deep past millions of years ago, when CO2 levels in the atmosphere were much higher than today. Robert Way goes medieval, looking at the medieval warm period just under 1,000 years ago. Andy Scuse looks at the Little Ice Age in the 1800s. And finally, well, it wasn't that far back in the past, but Daniel Bedford looks at what climate scientists were predicting in the 1970s. Climate scientists make predictions using climate models, which provide a number of insights into how future climate will behave. How do they do that? Dana Nietzsche-Talley explains how climate models are based on fundamental physical principles. That's how they're able to simulate how our climate behaves. He looks at how predictions based on physics tend to be a lot more accurate than predictions based on wishful thinking. Kier Shahneman will explain the difference between weather and climate. She'll also examine how climate scientists have a tendency to underestimate climate impacts. Lastly, we release interviews with scientists studying the Earth's past, as well as modeling future climate. And this week, we finally release part one of our trilogy, The Climate of Middle Earth. This features an interview with Dan Lunt, a climate scientist from the University of Bristol who built a computer model simulating the climate of middle Earth. Now this video isn't just an opportunity for Dan and myself to geek out about Lord of the Rings. There are actually some serious scientific insights into climate models to be found in this interview. But yes, simulating the climate of mortal is pretty cool. This week features part one of a three-part series. We didn't want to overwhelm you with too much middle Earth at once. So this week is a rich set of interesting lectures and fascinating interviews. I look forward to your comments in the discussion forum.