What are climate forcings?

Climate Forcings

The earths climate is affected by many things, these things are termed as climate forcings. They are called "forcings" because they force the climate system to change. Over the past thousand years the most important forcings on the climate have been variation in out put energy of the sun, volcanic eruptions, and lastly the most contributed human aspect is the change in green house gases in the atmosphere.[1]

Figure 1. Climate Forcings in the last 1000 years from CO2, Solar, and Volcanic [1]

Positive Forcings

These positive climate forces are factors that warm the earth. The major contributor of positive forcings to the earth are green house gases. Examples of these are Methane, CO2, CFCs, and N2O. These forcings are shown in red in figure 2.

Negative Forcing

These negative climate forces are factors that chill the earth. The major contributor of negative forcings are due to aerosols and forced cloud changes. These forces are shown in blue in figure 2.

Figure 2. Positive and Negative Climate Forcings [2]

Earths Albedo 

"Albedo" is reflective quality of a surface and is typically expressed as a percentage of reflected insolation to incoming insolation with 100% being total reflection. For example darker colors have much lower albedo then light colors.While smooth surfaces have high albedo and ruff surfaces are much lower. Earths albedo varies over lattitude but averages at about 31%. Although the albedo of the Earth near the poles can reach nearly 80%. [3]


[1] http://www.ncdc.noaa.gov/paleo/globalwarming/gw-forcing.html
[2] http://www.pnas.org/content/98/26/14778.full
[3] http://geography.about.com/od/physicalgeography/a/solarradiation.htm