<P> Air pollution is the introduction into the atmosphere of chemicals, particulate matter or biological materials that cause harm or discomfort to organisms . Stratospheric ozone depletion is caused by air pollution, chiefly from chlorofluorocarbons and other ozone - depleting substances . </P> <P> The scientific consensus is that the anthropogenic greenhouse gases currently accumulating in the atmosphere are the main cause of global warming . </P> <P> On October 19, 2015 NASA started a website containing daily images of the full sunlit side of Earth on http://epic.gsfc.nasa.gov/ . The images are taken from the Deep Space Climate Observatory (DSCOVR) and show Earth as it rotates during a day . </P>

Where is most of earth's mass located