Greenhouse effect and the ozone layer

Greenhouse Effect and the Ozone Layer Greenhouse Effect The trapping and build-up of heat in the lower atmosphere near a planet's surface. Some of the heat flowing back towards space from the Earth's surface is absorbed by water vapour, carbon dioxide, methane and other gases in the atmosphere. If the atmospheric concentration of these gases rises, then theory predicts that the average temperature of the lower atmosphere will gradually increase. The greenhouse effect in part explains the temperature differences of Mars, Venus and Earth.Enhanced Greenhouse Effect An increase in the natural process of the greenhouse effect, brought about by human activities, whereby greenhouse gases such as carbon dioxide, methane, chlorofluorocarbons and nitrous oxide are being released into the atmosphere at a far greater rate than would occur through natural processes and thus their concentrations are increasing. Also called anthropogenic greenhouse effect or climate change. The troposhpere allows solar radiation (shortwave radiation) but also traps some of the heat (longwave radiation). Without the troposhere the earth would be 30 degrees cooler than it is now. Greenhouse Gases Carbon DioxideThe increase in CO2 is partly caused by fossil-fuel burning, cement manufacture, land clearing, forest harvesting and changes in agricultural practice. According to the National Greenhouse Gas Inventory of 2005, CO2 accounts for 74.3 per cent of Australia's greenhouse gas emissions. Methane Emissions from landfill, biomass burning, increased agricultural production in rice paddy fields, digestive fermentation (burps and farts) from cattle and other livestock, and leaks from natural gas pipelines and coal mines have lead to a steady increase in methane emissions. Methane production accounts for only 20.2 per cent of Australia's greenhouse gas emissions. However, it is 20 times more potent as a greenhouse gas than CO2 and levels have increased at a faster rate. Scientists are concerned that global warming will result in the release of even more methane if permafrost melts. Nitrous Oxide There are many small sources of this gas both natural and manufactured that are difficult to quantify. The main sources created by human activity are from agriculture (especially the development of pastures in tropical regions), biomass burning and number of industrial processes. Nitrous oxide production accounts for only 4.3 per cent of Australia's greenhouse gas emissions but it is 200 to 300 times more potent as a greenhouse gas compared to CO2. Halocarbons Chlorofluorocarbons (CFCs) are halocarbons which were widely used for propellants, refrigerants, and foaming agents. Their use rapidly increased after their invention in the 1930s. The realisation that they were responsible for ozone depletion in the stratosphere has led to their phasing out under the 1987 Montreal Protocol. Perfluorocarbons, another type of halocarbon, are produced during aluminium production. Halocarbon production accounts for 1.1 per cent of Australia's greenhouse gas emissions (despite their small concentrations, halocarbons have a significant greenhouse effect). The Ozone Layer Ozone is a naturally occurring molecule containing three atoms of oxygen. Ozone molecules form a gaseous layer mostly in the upper atmosphere (the stratosphere) 15-30 km above the surface of the earth, and protects life on earth by absorbing ultra-violet (UV) radiation from the sun.