The Critical Zone

Greenhouse Gases, Aerosols and Radiative Forcing


Earth's surface temperature and climate are controlled by the amount of radiation received from the Sun: when incoming radiation is greater than outgoing radiation the Earth is warmed, and vice versa. Changes in the balance between incoming and outgoing radiation are referred to as radiative forcing. While the intensity or energy output from the Sun varies through time, other Earth-bound processes affect radiative forcing. For example, the gaseous and particulate composition of Earth's atmosphere plays an important role in controlling the energy balance. Changes in the natural landscape and human land-use also influence radiative forcing.

Reading Assignment

  • Visit the EPA's Atmospheric Changes site to learn more about the interaction between the greenhouse gas and aerosol composition of Earth's atmosphere and radiative forcing. Note: when you go to this site you'll find that the content is no longer available - I left this link in place so that you can experience the manner in which politics can play a role in science. The same goes on the next page, and assignment, relating to the use of information once provided by the US EPA.
  • See for what used to be the above link.
  • Also, visit the UNEP's Radiative Forcing page to better understand the effects of human activity on the composition of the atmosphere and Earth's climate.