2. FEEDBACK PARAMETERS Let T s = global mean surface air temperature R= net flux of heat into the climate system ΔR f = change in R due to some change in the forcing, e.g., a doubling of CO 2 ΔT s = equilibrium change in T s due to ΔR f

3. Define Feedback parameters: assuming the structure of the climate system is fixed due to changes in the structure i = 1, 2, 3, … If the perturbation is small then

4. FEEDBACKS AFFECTING CLIMATE SENSITIVITY i.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 = ?)

7. 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