Atmosphere of Earth development of animals. Today's atmosphere contains 21% oxygen, which is great enough for this rapid development of animals. "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. The scientific consensus is that the anthropogenic greenhouse gases currently accumulating in the atmosphere are the main cause of global warming. 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
Ozone layer The ozone layer (which absorbs from about 200 nm to 310 nm with a maximal absorption at about 250 nm) is very effective at screening out UV-B; for radiation with a wavelength of 290 nm, the intensity at the top of the atmosphere is 350 million times stronger than at the Earth's surface. Nevertheless, some UV-B, particularly at its longest wavelengths, reaches the surface, and is important for the skin's production of vitamin D. Ozone is transparent to most UV-A, so most of this longer-wavelength UV radiation reaches the surface, and it constitutes most of the UV reaching the Earth.