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Selasa, 31 Juli 2012

Global Warming (English)

So guys *ea, gua baru dapat tugas nih dari guru bahasa inggris gua tentang Global Warming. karena tugasnya dari guru bahasa inggris udah pasti dalam bahasa inggris dong. Jadi, nih bagi yang bernasib sama dengan gua semoga bisa membantu.


Global warming is the rise in the average temperature of Earth's atmosphere and oceans since the late 19th century, and its projected continuation. Since the early 20th century, Earth's mean surface temperature has increased by about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980. Warming of the climate system is unequivocal, and scientists are more than 90% certain that it is primarily caused by increasing concentrations of greenhouse gases produced by human activities such as deforestation and the burning of fossil fuels. These findings are recognized by the national science academies of all major industrialized nations.
            An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, as well as cause a probable expansion of subtropical deserts. Warming is expected to be strongest in the Arctic and would be associated with the continuing retreat of glaciers, permafrost and sea ice. Other likely effects of the warming include a more frequent occurrence of extreme-weather events including heat waves, droughts and heavy rainfall, species extinctions due to shifting temperature regimes, and changes in crop yields. Warming and related changes will vary from region to region around the globe, with projections being more robust in some areas than others. If global mean temperature increases to 4 °C (7.2 °F) above preindustrial levels, the limits for human adaptation are likely to be exceeded in many parts of the world, while the limits of adaptation for natural systems would largely be exceeded throughout the world. Hence, the ecosystem services upon which human livelihoods depend would not be preserved.
An example of the cause of Global warming is The greenhouse effect. The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet's lower atmosphere and surface. It was proposed by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896.
Naturally occurring amounts of greenhouse gases have a mean warming effect of about 33 °C (59 °F). The major greenhouse gases arewater vapor, which causes about 36–70% of the greenhouse effect; carbon dioxide (CO2), which causes 9–26%; methane (CH4), which causes 4–9%; and ozone (O3), which causes 3–7%. Clouds also affect the radiation balance through cloud forcings similar to greenhouse gases. Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, leading to increased radiative forcing from CO2, methane, tropospheric ozone, CFCs and nitrous oxide. The concentrations of CO2 and methane have increased by 36% and 148% respectively since 1750. These levels are much higher than at any time during the last 800,000 years, the period for which reliable data has been extracted from ice cores. Less direct geological evidence indicates that CO2 values higher than this were last seen about 20 million years ago. Fossil fuel burning has produced about three-quarters of the increase in CO2 from human activity over the past 20 years. The rest of this increase is caused mostly by changes in land-use, particularly deforestation

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