Experts estimate that we need to reduce global emissions of most greenhouse gases by 60 to 80 percent if we want to stop contributing to global warming. Data collected since the 1950s leads scientists to believe that ozone levels were relatively stable until the late 1970s. Severe depletion over the Antarctic has been occurring since 1979 and a general downturn in global ozone levels has been observed since the early 1980s. Global ozone levels declined an average of about three percent between 1979 and 1991. This rate of decline is about three times faster than that recorded in the 1970s.
Smog can be harmful to the health of humans, animals and plant life including essential food crops.
Imagine the Earth as a beach ball one metre in diameter, with a skin one millimetre thick. The entire biosphere - the surface of the Earth and all life on the planet, would be only as thick as the beach balls' plastic skin. Earth is able to support life because of its fragile but protective atmosphere. Without the atmosphere, the Earth's average temperature would be minus 18 degrees Celsius, too cold to sustain life. Brown smog, known as Arctic Haze, is found over the High Artic, far away from the actual source.