THE EARTH'S CLIMATE system is characterized by the energy balance of the Earth, the distribution of energy in space (or Earths atmosphere), and temporal energy variation. The Earth s radiative energy balance is governed by the balance between the solar radiation and absorption by the Earth, and subsequent radiation from the Earth to outer space. The absorbed solar shortwave radiation by Earth is emitted back to outer space in thermal infrared or longwave radiation to maintain the Earths heat energy balance. The imbalance (surplus) in the Earths energy budget leads to global warming.

In the 20th century, according to global temperature records, the near surface of the Earth warmed by nearly 1.0 degree F (0.6 degrees C). This global warming is due to anthropogenic climate-forcing agents, ...