FEEDBACK PARAMETERS
Let Ts= global mean surface air temperature
R= net flux of heat into the climate
system
ΔRf = change in R due to some change in
the forcing, e.g., a doubling of CO2
ΔTs = equilibrium change in Ts due to ΔRf
Define Feedback parameters:
0
R

Ts
i 
R
Ts
f
i
assuming the structure of the
climate system is fixed
due to changes in the structure i =
1, 2, 3, …
i  0  stabilizing , i  0  destabilizing
If the perturbation is small then
Ts 
 R f


n 0
i
FEEDBACKS AFFECTING
CLIMATE SENSITIVITY
Stefan-Boltzmann Law (negative, λ = 3.3 W/m2/K)
ii. Water Vapor Feedback (positive, λ = 1 to
1.5 W/m2/K)
iii. Ice/Snow Albedo Feedback (positive, λ =
0.1 to 0.5 W/m2/K)
iv. Cloud Feedback (λ = ?)
i.
The equilibrium global mean SAT warming
for a doubling of atmospheric carbon
dioxide (CO2), or ‘equilibrium climate
sensitivity’, is likely to lie in the range 2°C
to 4.5°C, with a most likely value of about
3°C.
IPCC 4AR Chapter 10