Meet the Scientist Who Wants to Alter Earth’s Atmosphere

From his glass-walled, 57th-floor apartment overlooking Chicago, David Keith can see the whole of the sky. When I visited him there on a clear day this summer, the pale blue stretched from the surface of Lake Michigan up toward the edge of space.It is up there in the stratosphere that Keith, a professor in the University of Chicago’s department of geophysical sciences, wants to alter the very composition of the…