 Welcome to week 3 of Denial 101x. Last week we looked at all the evidence that global warming is happening. So this week we asked the question, what's causing it? We answer that in three parts. Firstly, Gavin Corley and Andy Scoose examine how carbon moves around our climate system, otherwise known as the carbon cycle. Understanding the carbon cycle helps you understand the effect of humans adding billions of tons of carbon dioxide to the atmosphere. Secondly, what's the effect of adding carbon dioxide to the atmosphere? Well, carbon dioxide is a greenhouse gas, which means it traps heat. Mark Richardson and Sarah Green look at the greenhouse effect in more detail. Lastly, if an increased greenhouse effect is causing global warming, then we should expect to see human fingerprints all over our climate. So finally, in week 3, Dana Nicciutelli, Mark Richardson and Sarah Green will take us through the observations that scientists have been collecting looking for human fingerprints that would indicate human cause global warming. I also interviewed scientists studying the carbon cycle as well as a leading expert in human fingerprinting, Ben Santa. He authored the famous statement in the 1995 IPCC report about the balance of evidence suggesting and discernible human influence on global climate. So I hope you enjoy our week 3 lectures and interviews, as well as interacting with your fellow students.