(Note: This interview originally aired back in October.) What's it like to live on one-tenth of the fossil-fuel consumption of the average American? Alarmed by the drastic changes now occurring in the Earth's climate systems, our guest on today's ST -- who is a climate scientist and father of two -- decided to find out. And he's very glad he did. Peter Kalmus is our guest; he is an atmospheric scientist at Caltech / Jet Propulsion Laboratory, and he has a book out. As he announces in this book, he eventually made a decision to change both his life and the world...and in both cases, for the better. So he began by bicycling, growing food in his backyard, meditating, and making other simple yet fulfilling changes. Ultimately, as he tells us today, Kalmus slashed his climate impact to one-tenth of the U.S. average -- and he became a happier person in the process.