On November 2, 2011, Richard Alley participated in The National Climate Seminar, a series of webinars sponsored by Bard College's Center for Environmental Policy. The online seminars provide a forum for leading scientists, writers, and other experts to talk about critical issues regarding climate change. The series also opens a public conversation, inviting participants to ask questions and contribute their own thoughts.

Dr. Alley conducts research on the paleoclimatic record at The Pennsylvania State University in order to understand the history, and perhaps the future, of climate change. In his lecture, Alley gave a concise overview of why we know what we know about climate change, and what that evidence can tell us about today's warming planet. Alley not only provides an accessible science lesson, but reveals his own greatest concerns about climate change and offers advice to those who want to stop debating the subtleties of climate science and act now.

This E-ssential is an edited version of Alley's talk and the subsequent question and answer session. While some material has been cut and some language modified for clarity, the intention was to retain the substance of the original discussion.