Earth's radiative forcing is the change over time of the net difference between the amount of the planet's incoming radiation energy and the amount of its outgoing radiation energy (the net irradiance).

This differential is measured at the tropopause, the boundary in the atmosphere between the troposphere and the stratosphere. When there is more incoming than outgoing radiation energy, corresponding to positive radiative forcing, the average temperature of the Earth rises. When there is more outgoing than incoming radiation energy (negative radiative forcing), the average temperature decreases. Changes in radiation forcing can be produced by a variety of agents, most notably varying radiation outputs from the Sun or variations in the concentrations of greenhouse gases (GHGs) in the atmosphere.

The Intergovernmental Panel on Climate Change (IPCC) requires that values of radiative forcing be reported relative to the year 1750, which is taken as the beginning of the industrial era (Axelrod, 2004). When the Earth's radiative balance strays away from its equilibrium state, global temperatures change. A linear relationship has been established between the amount of radiative forcing and the average global equilibrium surface temperature. The change in radiative forcing is equal to the change in global temperature multiplied by the climate sensitivity, or radiative damping, coefficient. Values of radiative forcing are reported in watts per square meter. The Earth's radiation balance is directly influenced by changes in atmospheric composition, cloud properties, and surface and atmospheric temperatures.

Since radiative forcing is rather easy to calculate, it provides a general estimate of climate changes due to variations in the radiation output of the Sun, changes in GHG concentrations, changes produced by emission of heat by various materials, and other agents that change the net amount of radiation energy. Since the majority of energy that affects the Earth's climate comes from the Sun, if radiative forcing were close to zero, the solar radiation energy coming to the Earth would be approximately equal to the infrared radiation emitted from the Earth (Botterill, 2003).

Radiative forcing values are estimated by inputting available weather data into computer algorithms that are based on general circulation models (GCMs). Values are generated for contributions due to natural influences, particularly varying solar radiation, volcanic eruptions, and seasonal effects that alter cloud and ground cover, and for human contributions, particularly GHG emissions and aerosols. Some calculations indicate that the radiative forcing caused by human activities is more influential on climate change than is the radiative forcing caused by natural means. Other calculations indicate the opposite. In either scenario, reduction of GHG emissions is an important goal in regulating the Earth's climate.

References

1. Axelrod, Regina S., David Leonard Downie, and Norman J. Vig, eds. The Global Environment: Institutions, Law, and Policy. 2d ed. Washington, D.C.: CQ Press, 2004.

2. Botterill, Linda C., and Melanie Fisher, eds. Beyond Drought: People, Policy, and Perspectives. Collingwood, Vic.: CSIRO, 2003.

Free term papers are not written to satisfy your specific instructions. You can use our professional writing services to buy a custom written research paper, term paper, or essay on Global Warming at affordable price. CustomTermPapers is the best solution for those who seek help in writing term papers, essays, and research papers related to Global Warming and other relevant topics.