Climate change milestone

Guests: Gavin Schmidt, Anthony Leiserowitz

Last week carbon dioxide in the atmosphere reached record levels — 400 parts per million, according to a monitoring station in Hawaii.  Never in human history have carbon dioxide concentrations been that high.  Scientists have warned that these high levels mark a milestone in our climate and could alter it significant ways.  This hour, have we reached a climate tipping point?  We’ll also check in on American’s attitudes toward climate change.  Marty talks with GAVIN SCHMIDT, climate scientist at the NASA Goddard Institute for Space Studies, and ANTHONY LEISEROWITZ, Director of the Yale Project on Climate Change Communication.