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Environment Solar irradiation Solar irradiation describes the visible and near-visible (ultraviolet and near-infrared) radiation emitted from the sun. Terrestrial radiation is a term used to describe infrared radiation emitted from the atmosphere. Outside the earth's atmosphere, Solar irradiation has an intensity of approximately 1370 watts/m2. This is the value at mean earth-sun distance at the top of the atmosphere and is referred to as the Solar Constant. On the surface of the earth on a clear day, at noon, the direct beam radiation will be approximately 1000 watts/m2 for many locations. The availability of energy is affected by location (including latitude and elevation), season, and time of day. All of which can be readily determined. However, the biggest factors affecting the available energy are cloud cover and other meteorological conditions which vary with location and time. The use of Solar irradiation is the most readily accessible resource in South Africa. Most areas in South Africa average more than 2 500 hours of sunshine per year, and average solar-radiation levels range between 4.5 and 6.5kWh/m2 in one day. The southern African region, and in fact the whole of Africa, has sunshine all year round. The annual 24-hour global Solar irradiation average is about 220 W/m2 for South Africa, compared with about 150 W/m2 for parts of the USA, and about 100 W/m2 for Europe and the United Kingdom. This makes sunshine one of South Africa's most valuable local resources and solar renewable energy a logical solution to the global energy crisis. Global warming Global warming is the increase in the average temperature of the Earth's near-surface air and oceans. This increase has been observed since the middle of the last century and is projected to continue. Global surface temperature has increased by less than 1degree Celsius over this period. The Intergovernmental Panel on Climate Change (IPCC) concludes that Greenhouse gases are responsible for most of the observed temperature increase since the middle of the twentieth century, while natural phenomena such as solar variation and volcanoes produced most of the warming from pre-industrial times to 1950 and had a small cooling effect afterward. These basic conclusions have been endorsed by more than 40 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries. Climate model projections summarized in the latest IPCC report indicate that global surface temperature will probably rise a further 1.1 to 6.4 °C during the twenty-first century. The uncertainty in this estimate arises from the use of models with differing climate sensitivity, and the use of differing estimates of future greenhouse gas emissions. Some other uncertainties include how warming and related changes will vary from region to region around the globe. Increasing global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts. The continuing retreat of glaciers, permafrost and sea ice is expected, with the Arctic region being particularly affected. Other likely effects include shrinkage of the Amazon rainforest and Boreal forests, increases in the intensity of extreme weather events, species extinctions and changes in agricultural yields. If global warming continues, excess heat and carbon dioxide trapped in the oceans may still take hundreds years to be re-emitted, even after greenhouse gas emissions are eventually reduced. CO2 concentrations are continuing to rise due to burning of fossil fuels and land-use change. The future rate of rise will depend on uncertain economic, sociological, technological, and natural developments. Political and public debate continues regarding the appropriate response to global warming. The available options are the reduction of further greenhouse gas emissions; adaptation to reduce the damage caused by warming; and, more speculatively, Geoengineering to reverse global warming. Most national governments have signed and are implementing the Kyoto Protocol aimed at reducing greenhouse gas emissions. The Kyoto Agreement is the world's primary international agreement on reducing greenhouse gas emissions. The Protocol now covers more than 160 countries and over 55 percent of global greenhouse gas emissions. Only the United States and Kazakhstan have not ratified the treaty, with the United States historically being the world's largest emitter of greenhouse gases. Whatever the future, it is certain that we each, as individuals and businesses, must take responsibility for our contribution to global warming and must undertake individual action against it. Main greenhouse gases:
Earth's Solar irradiation
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