On the Confusion of Planck Feedback Parameters

The Planck feedback parameter I› 0 is the most fundamental quantity in the theory of global warming, because the surface temperature change I”T s,0 is calculated by—(radiative forcing due to CO 2 doubling)/I› 0 in the absence of feedbacks other than that of surface temperature change. The following three groups of Planck feedback parameters are found in the literature depending on the choice of temperature T s and the outgoing long wave radiation (OLR) at the top of atmosphere in equation of I› 0 = −4OLR/T s , which is derived from the Stefan-Boltzmann Law. GROUP A: T s = 288K and OLR = 231–243W/m 2 I› 0 = −3.21 − −3.37(W/m 2 )/K GROUP B: T s = 255K and OLR = 242W/m 2 , I› 0 = −3.8(W/m 2 )/K GROUP C: T s = 288K and OLR = 492–514W/m 2 I› 0 = −6.8 – −7.1(W/m 2 )/K This study shows that I› 0 of GROUP C is a theoretically relevant choice for T s and OLR, rather than those of GROUP A and GROUP B, while the IPCC adopted I› 0 of GROUP A. Although the surface temperature change I” T s is 3.0K with I› 0 = −3.21(W/m 2 )/K for CO 2 doubling when lapse rate, water vapor, surface albedo and cloud feedbacks are included in the IPCC AR4, it is shown to be 0.5–0.75K with I› 0 = −6.8(W/m 2 )/K in the present study. Since the IPCC overestimates the threat of carbon dioxide by 4–6 times, the revaluation will be needed for the CO 2 reduction policies in terms of cost and potential hazards.