Fundamentals of geology I. (lithosphere) 1 1. The formation of the Earth 1
Fig. 9.5. Process of greenhouse effect
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- Fig. 9.6. The origin and distribution of the greenhouse gases (www.mti.hu) 9.4. 9.4. Radiation pollution
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Fig. 9.5. Process of greenhouse effect The major greenhouse gases in the atmosphere are carbon dioxide (CO2), methane, (CH4), nitrous oxide (N2O), chlorofluorocarbons (CFCs) and ozone (O3). Atmospheric water vapour (H2O) also makes a large contribution to the natural greenhouse effect but it is thought that its presence is not directly affected by human activity. Due to greenhouse gases, the atmosphere absorbs more infrared energy than it re-radiates to space, resulting in a net warming of the Earth-atmosphere system and of surface temperature. This is the "Natural Greenhouse Effect". With more greenhouse gases released to the atmosphere due to human activity, more infrared radiation will be trapped in the Earth's surface which contributes to the "Enhanced Greenhouse Effect". Since the mid 1800's the average concentration of CO2 in the earth's atmosphere has risen from about 280 parts per million (ppm) to just over 383 ppm in 2007, and methane from about 800 part per billion (ppb) to around 1790 ppb in 2008. While these changes represent only a very small change to the overall composition of the earth's atmosphere, it is a significant change to its capacity to absorb and emit heat. The main contributors are changes to the carbon cycle that have led to increased levels of carbon dioxide in the earth's atmosphere in the last 200 years. These include reduced CO2 removal and storage through deforestation; direct CO2 production from the burning of fossil fuels and CO2 released from cement production. The increased release of nitrogen oxides (NOx) from burning fossil fuels and soil denitrification and intensive production of livestock such as cows and pigs which produce methane have also contributed to the enhanced greenhouse effect. The differing chemical structures of these gases produce a different absorption spectra or wavelengths of radiation which they will absorb or let through. However, CO2 and other greenhouse gases can absorb the infrared radiation at the wavelengths missed by water vapour. Note that while methane (CH4) and N2O both absorb more heat per molecule than CO2, CO2 concentrations are much higher (100 -100 times higher respectively) and therefore have more overall effect on the enhanced greenhouse effect. Residence time plays an important role as well as concentration. While water vapour is by far the greatest contributor to the natural greenhouse effect, it spends so little time in the atmosphere (days rather than centuries) that it is not well mixed and thus its effects on temperature are short lived and very localised (Pict. 9.6.). 
Fig. 9.6. The origin and distribution of the greenhouse gases (www.mti.hu) 9.4. 9.4. Radiation pollution Radiation pollution is any form of ionizing or nonionizing radiation that results from human activities. The most well-known radiation results from the detonation of nuclear devices and the controlled release of energy by nuclear-power generating plants (see nuclear energy). Other sources of radiation include spent-fuel reprocessing plants, by-products of mining operations, and experimental research laboratories. Increased exposure to medical X rays and to radiation emissions from microwave ovens and other household appliances, although of considerably less magnitude, all constitute sources of environmental radiation (Fig. 9.7.). 
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