In this lecture professor Michael B. McElroy introduces the worldwide experiment we have embarked on through the increase in global temperature. He covers some of the basics of global warming such as the greenhouse effect, the gases that contribute to global warming, and what creates the climate on Earth. He then puts humanity and global warming in the context of Earth's entire history going back 4.5 billion years ago. He uses a calendar year as a reference for Earth's history and places global warming at the last few seconds before midnight on December 31st. It's an excellent introductory lecture for placing global warming in global history.