As the comment from Covey et al makes clear, he is calculating a sensitivity to surface energy fluxes that is almost 100x larger than
standard estimates of the climate sensitivity.
Not exact matches
Other ways that the
standard or «consensus» calculations bias the
climate sensitivity upward also exist and are also not negligible (or at least there is no scientific case that they are negligible), but for now it is sufficient to think about, and try to
estimate, the magnitude
of the increase in H2O and latent heat flow from surface to upper troposphere.
Assuming the same
climate sensitivity, Lindzen's
estimate of a 2.5 °C drop for a -30 W / m2 forcing would imply that currently doubling CO2 would warm the planet by only a third
of a degree at equilibrium, which is well outside the bounds
of IPCC
estimates and even very low by most skeptical
standards.
The
standard modern
estimate of climate sensitivity — 3 °C, plus or minus 1.5 °C — originates with a committee on anthropogenic global warming convened in 1979 by the National Academy
of Sciences and chaired by Jule Charney.
The IPCC gets its 2 - 4.5 C
climate sensitivity range from Table 8.2
of the AR4, which lists 19
climate model - derived equilibrium
sensitivity estimates that have a mean
of 3.2 C and a
standard deviation
of 0.7 C.
Using feedback parameters from Fig. 8.14, it can be
estimated that in the presence
of water vapor, lapse rate and surface albedo feedbacks, but in the absence
of cloud feedbacks, current GCMs would predict a
climate sensitivity (± 1
standard deviation)
of roughly 1.9 °C ± 0.15 °C (ignoring spread from radiative forcing differences).
[8] I
estimate GISS - E2 - R's effective
climate sensitivity applicable to the historical period as 1.9 °C and its ERF F2xCO2 as 4.5 Wm − 2, implying a
climate feedback parameter
of 2.37 Wm − 2 K − 1, based on a
standard Gregory plot regression
of (ΔF − ΔN) on ΔT for 35 years following an abrupt quadrupling
of CO2 concentration.