Global warming.

Abstract

Global warming is the current increase in temperature of the Earth’s surface (both land and water) as well as its atmosphere. Average temperatures around the world have risen by 0.75 ° C (1.4 ° F) over the last 100 years. About two thirds of this increase has occurred since 1975. In the past, when the Earth experienced a rise in temperature it was the natural causes but today it is being caused by the accumulation of greenhouse gases in the atmosphere produced by human activities. Global warming occurs when carbon dioxide (CO2) and other air pollutants and greenhouse gasses collect in the atmosphere and absorb sunlight and solar radiation that have bounced off the earth’s surface. Normally, this radiation would escape into space—but these pollutants, which can last for years to centuries in the atmosphere, trap the heat and cause the planet to get hotter. That’s what’s known as the greenhouse effect. The "greenhouse effect" is the warming that happens when certain gases in Earth’s atmosphere trap heat. These gases let in light but keep heat from escaping, like the glass walls of a greenhouse.