Institute for Advanced Study Astrophysics Seminar

ABSTRACT: The 20th Century has seen a notable temperature rise, generally attributed to the greenhouse effect of anthropogenic gases, and a future "business as usual" policy is generally believed to be catastrophic. I will show, however, that the story is not that simple. I will address the following questions,all of which have a far from trivial and often surprising answer: How large is the greenhouse effect? Could some of the temperature rise be natural and not anthropogenic? If so, what is this natural driver? How sensitive really is Earth's climate? What should we expect in the future? How effective will the implementation of a cap and trade agreement be?