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.