Unformatted text preview: lead to warming of climate and surface albedo, aerosols and contrails. The
cooling. The thin black line attached to each coloured bar represents the range of uncertainty for the respective
only increase in natural forcing of any significance between 1750 and 2005 occurred in solar
value. (Figure adapted from Figure 2.20 of this report.)
irradiance. Positive forcings lead to warming and negative forcings lead to cooling. (source:
IPCC report) FAQ 2.1, Box 1: What is Radiative Forcing?
adiative forcing? The in uence of a factor that can cause climate change, such as a greenhouse gas, is often evaluated in
radiative forcing. Radiative forcing is a measure of how the energy balance of the Earth-atmosphere system is in uenced
s that a ect climate are altered. The word radiative arises because these factors change the balance between incoming solar
d outgoing infrared radiation within the Earth’s atmosphere. This radiative balance controls the Earth’s surface temperature.
cing is used to indicate that Earth’s radiative balance is being pushed away from its normal state.
forcing is usually quanti ed as the ‘rate of energy change per unit area of the globe as measured at the top of the atmois expressed in units of ‘Watts per square metre’ (see Figure 2). When radiative forcing from a factor or group of factors
as positive, the energy of the Earth-atmosphere system will ultimately increase, leading to a warming of the system. In
a negative radiative forcing, the energy will ultimately decrease, leading to a cooling of the system. Important challenges
cientists are to identify all the factors that a ect climate and the mechanisms by which they exert a forcing, to quantify the
cing of each factor and to evaluate the total radiative forcing from the group of factors.
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This document was uploaded on 11/21/2013.
- Fall '08