Riley Duren, the chief systems engineer for the Earth Science and Technology Directorate at NASA’s Jet Propulsion Laboratory(JPL), shows the global map of carbon dioxide at Mount Wilson, Calif., Friday, April 12, 2013. A mile above this city, sensors gaze down on the basin from atop Mount Wilson the way a satellite fixates on Earth, collecting pieces of information about Los Angeles’ carbon footprint. (AP Photo/Jae C. Hong)

Read: Project Aims to Track Big City Carbon Footprints

Riley Duren, the chief systems engineer for the Earth Science and Technology Directorate at NASA’s Jet Propulsion Laboratory(JPL) demonstrates on the laser radar designed to measure carbon dioxide in the air at Caltech’s Linde + Robinson Laboratory in Pasadena, Calif.

Senior research scientist Stanley Sander stands on the rooftop of the California Laboratory for Atmospheric. Remote Sensing (CLARS) facility at Mount Wilson, Calif.

Palm trees are seen through an observatory door at Caltech’s Linde + Robinson Laboratory.