On the Confusion of Planck Feedback Parameters

Abstract

The Planck feedback parameter Λ0 is the most fundamental quantity in the theory of global warming, because the surface temperature change ΔTs,0 is calculated by—(radiative forcing due to CO2 doubling)/Λ0 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 Ts and the outgoing long wave radiation (OLR) at the top of atmosphere in equation of Λ0 = −4OLR/Ts, which is derived from the Stefan-Boltzmann Law. GROUP A: Ts = 288K and OLR = 231–243W/m2 Λ0 = −3.21 − −3.37(W/m2)/K GROUP B: Ts = 255K and OLR = 242W/m2, Λ0 = −3.8(W/m2)/K GROUP C: Ts = 288K and OLR = 492–514W/m2 Λ0 = −6.8 – −7.1(W/m2)/K This study shows that Λ0 of GROUP C is a theoretically relevant choice for Ts and OLR, rather than those of GROUP A and GROUP B, while the IPCC adopted Λ0 of GROUP A. Although the surface temperature change Δ Ts is 3.0K with Λ0 = −3.21(W/m2)/K for CO2 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 Λ0 = −6.8(W/m2)/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 CO2 reduction policies in terms of cost and potential hazards.