According to the definition provided by the IPCC (Intergovernmental Panel on Climate Change), radiative forcing is " the equilibrium between incoming solar radiation and infrared radiation emissions leaving the atmosphere ". It is measured in W/m².
The IPCC uses this term to evaluate the impact of different factors (CO2 emissions, albedo, aerosols, etc.) on the energy budget of the Earth.
Negative and positive radiative forcing
The Earth receives energy in the form of heat, through the sun's rays. Certain factors, typically greenhouse effect gases, tend to absorb infrared radiation. Thus, the more they are present in the atmosphere, the more the climate warms. Radiative forcing of greenhouse effect gas is therefore positive.
On the other hand, aerosols tend to reflect solar rays back to their emitter, which causes the Earth to cool. In this case, radiative forcing is negative.
If the overall radiative forcing is positive, the Earth tends to warm. This is what is currently happening. In the opposite case, it cools.
As the World Meteorological Organisation notes, radiative forcing imputable to greenhouse effect gas continues to increase. © OMM 2011
Radiative forcing - 1 Photo