Global Warming

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. During the 21st century the global surface temperature is likely to rise a further 1.1 to 2.9 °C (2 to 5.2 °F) for their lowest emissions scenario and 2.4 to 6.4 °C (4.3 to 11.5 °F) for their highest Global warming begins when sunlight reaches Earth. The clouds, atmospheric particles, reflective ground surfaces and ocean surface then reflected about 30 percent of it back into space, while the remaining is absorbed by oceans, lands and air. This in turn heats the planet’s surface and atmosphere, making life possible. As Earth warmed up, this solar energy is radiated by thermal radiation or infrared heat, travelling directly out to space, thus cooling the Earth. However, some of the outgoing radiation is re-absorbed by carbon dioxide, water vapor and other gases in the atmosphere and is radiated back to Earth’s surface; these gases are known as greenhouse gases due to their heat-trapping capacity. This re-absorption process is naturally good; the Earth’s average surface temperature would be very cold if not for the greenhouse gases. The problem begins when the concentration of greenhouse gases in the atmosphere were artificially raised by humankind at an ever-increasing rate since the past 250 years. As of 2004, over 8 billion tons of carbon dioxide was pumped out per year; natural carbon sinks such as forests and the ocean absorbed some of this, while the rest accumulated in the atmosphere.
The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an...