Analyse+different+scientific+veiws+of+the+causes+of+global+warming+to+assess+predictions+on+the+likelyhood+of+global+warming.

**analyse different scientific views on the causes of global warming to assess predictions on the likelihood of global warming** >> //Carbon dioxide//-Since 1850, there has been a mean rise in global temperature of approximately 0.74 ± 0.18 °C with most of this increase since 1960. Carbon dioxide levels have risen from 280 ppm in 1850 to 390 ppm in 2009. Since the Industrial Revolution human activities have seen massive amounts of fossil fuel being burnt to generate electricity, fuel furnaces and operate smelters. Other causes of rising CO2 today are cement manufacture, land clearing, forest harvesting and changes in agricultural practice. These, combined with the burning of fuel in motor vehicles, has resulted in massive amounts of carbon dioxide being emitted into the atmosphere. According to the National Greenhouse Gas Inventory of 2005, CO2 accounts for 74.3 per cent of Australia's greenhouse gas emissions. >> //Methane//: Given that methane has eleven times more warming potential than carbon dioxide, processes affecting the release of methane into the atmosphere should be given great consideration. Massive amounts of methane are currently stored in clathrates, also known as gas hydrates, which occur abundantly in nature. Clathrates occur as a result of organic matter decomposing and the methane that results becoming entrapped. Most of the methane gas is trapped in ocean sediments. However, some methane is trapped in ice in Arctic regions and regions in the tundra. The worldwide amounts of carbon bound in clathrates are conservatively estimated to total twice the amount of carbon to be found in all known fossil fuels on Earth. The methane trapped as clathrates in ice can be released into the atmosphere. This happens after ice sheets melt or in the case of clathrates layers in ocean sediments, the pressure of the water above them is reduced. >> Is there a greenhouse effect? A few scientists reject this theory, claiming that the global warming that is currently observed is predictable as a natural cyclic process of the Earth but most scientists, especially those who work in the field of atmospheric science and climate change, agree that the enhanced greenhouse effect is resulting in serious climate change. >> Some scientists indicate that the rate of release of greenhouse gases must be reduced. There is concern that the rate of reduction that is desired may not be achieved by enough nations to have a global impact. >> A number of global climate models have been developed that assist scientists to make predictions about the effects of global warming. However, there is concern by some scientists that these models may not be accurate enough for policy makers to determine what actions should be taken.
 * Most scientists in the climate change field believe that rises in carbon dioxide emissions and other gases such as methane and nitrous oxide have been directly responsible for rises in global temperatures. However, there are a few scientists who argue that this temperature rise could just be part of natural fluctuations in the absorption and emission of such things as methane gas.
 * There are a number of different scientific views on the causes of global warming but the overwhelming scientific opinion is that greenhouse gas emissions such as the ones listed above are rising and this is due to human activity. The main gases and their sources are:
 * It is difficult to develop accurate computer models to predict the effect on climate due to the large number of variables involved with the greenhouse effect. For example, the effect of cloud cover: clouds reflect the incoming light and absorb outgoing infra-red radiation. The magnitude of its effect depends upon the degree of cloud cover, its altitude and thickness. Scientists views on the effect of cloud cover vary from no greenhouse effect to a mean 2oC temperature rise over 100 years.
 * Debate about global warming centres on the following points: