Feature Guest: Susan Strahan While human activity is what created the ozone hole, scientists just announced direct evidence that human activity is now responsible for healing that damage. That makes the Montreal Protocol, which banned the emission of chlorofluorocarbons or CFCs, along with other ozone depleting substances, the most successful international environmental agreement to date. Today we’re joined at The Star Spot by Dr. Susan Strahan, who lead a team that studied the reduction of CFCs, to discuss the fall and rise of the ozone layer and what this means for future efforts to achieve international cooperation on critical environmental issues like climate change. Current in Space Tabby's star may no longer be the megastructure of another species, but as Tony explains, the way in which we figured that out says quite a lot about this one.  About Our Guest Susan E. Strahan is atmospheric scientist at NASA’s Goddard Space Flight Center where she works in the Atmospheric Chemistry and Dynamics Branch. She holds a PhD in Chemistry from the University of California Berkeley. Her research involves making stratospheric trace gas measurements and studying chemistry-climate models. She is a member of the American Geophysical Union and the American Meteorological Society.