The primary source of warmth for the Earth is radiant energy provided by our Sun. Just as the Sun radiates energy into space, the Earth, being warmer than space, also radiates energy out into space. Most of the energy it radiates into space is in the form of infra-red radiation, though light is a contributor as well. The Earth will radiate about the same amount of energy into space as it receives from the Sun on average. The Earth is often called a black body radiator, though this is not technically correct.
The energy equilibrium with the Sun ignores some heat from the Earth’s core, energy due to the Earth’s magnetic field interactions with the magnetic field of the Sun, gravitational tide effects due to the moon, or energy due to material from space entering our atmosphere at high speeds. It is commonly claimed by those who advocate catastrophic global warming due to man’s emissions of carbon dioxide that the total greenhouse gas effect is a warming of the Earth’s surface by about 33ºC.
They say this warming is caused by the infra-red (IR) radiation absorbing gases of water vapor, carbon dioxide, and methane in the atmosphere. These gases are said to cause the Earth to retain and even multiply the energy it receives from the Sun, so that the Earth’s surface is warmer than it would otherwise be. Of these gases, water vapor is much the most important, but carbon dioxide is said to have a large enough effect that man’s additions to the concentrations in the atmosphere will do serious harm to the Earth’s flora and fauna, as well as man himself.