Want more? Subscribe to NASA on iTunes! http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=283424434 Climate scientists have been monitoring Earth's energy budget since the 1978 launch of NASA's Nimbus-7 satellite. That mission carried a new instrument into space called the Earth Radiation Budget Experiment (or ERBE), designed to measure all of the energy leaving through the top of Earth's atmosphere. All of the incoming sunlight minus all of the reflected sunlight and emitted heat is our world's energy budget. The second law of thermodynamics compels Earth's climate system to seek equilibrium so that, over the course of a year the amount of energy received equals the amount of energy lost to space. So typically the global energy budget is in balance. Goddard's Dr. Marc Imhoff discusses similar climate-monitoring functions of NASA's Terra satellite in this video. For more info: http://www.nasa.gov/centers/goddard/news/topstory/2008/esw_videos.html