In this episode of Rationally Speaking, Julia and Massimo talk to physicist and climatologist Michael Mann about how we know the climate is getting warmer. Among other things, they cover the physical processes of climate change, the role that predictive models have played in confirming scientists' theories about the rate of warming, and what are uncertainties in the science. Also, how optimistic we should be about technological solutions to the problem.

Dr. Michael E. Mann is Distinguished Professor of Meteorology at Penn State University, with joint appointments in the Department of Geosciences and the Earth and Environmental Systems Institute. He is also director of the Penn State Earth System Science Center. Dr. Mann is author of more than 160 peer-reviewed and edited publications, and has published two books including Dire Predictions: "Understanding Global Warming in 2008 and The Hockey Stick and the Climate Wars: Dispatches from the Front Lines" in 2012. He is also a co-founder and avid contributor to the award-winning science website RealClimate.org.