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. scientists are more than 90% certain that it is primarily caused by increasing concentrations of greenhouse gasses produced by human activities. A greenhouse gas (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect.The primary greenhouse gases in the Earth's atmosphere are water vapour, carbon dioxide, methane, nitrous oxide, and ozone. The causes of increasing greenhouse gases are: Burning fossil fuels, thus releasing into the atmosphere carbon that has been safely stored for millions of years by burning coal, oil and natural gas for transport and electricity. An enormous demand for electricity. The growing population of the earth all want cars, refrigerators, air-conditioning and a double garage. Most electricity is generated by burning coal. A constant and growing demand for red meat. Cattle belch out methane, a toxic greenhouse gas, much more dangerous than carbon dioxide. More and more forests and bushland, which absorb carbon dioxide from the air, are being cut down so more cattle can graze. A reduction in the planet's ability to remove greenhouse gases from the atmosphere. The earth has natural sources of carbon dioxide (a greenhouse gas), and has had long before mankind began altering the environment, but the earth has natural means to actually remove some greenhouse gases from the atmosphere, especially carbon dioxide which is removed by plants (especially dense, tall forests) through photosynthesis. Global deforestation