A flexible system such as cap and trade would likely be essential if we found that the worst -
case feedback values were more probable than originally anticipated.
If peak Phanerozoic ca is of the order of 1000 ppm then either slow - feedback climate sensitivity is greater than the canonical fast
feedback value of 3 °C for 2 × CO2 [Solomon et al., 2007], or global temperatures have been no warmer than ~ 6 °C above preindustrial conditions.
When you consider that the «Greenhouse» effect is logarithmic, wouldn't that affect subsequent water
vapor feedback values?
Once you have established these two values you can then add in the IPCC contributors and the variability of their values plus their forcing or
feedback values to determine if the contributor values result in a positive or negative value in relation between the gold standard and the observational data.
I thought that the rough numbers were that the water vapor feedback about doubles the climate sensitivity from the no -
feedback value and then the lapse rate feedback takes about half of that back, leaving about a 1.5X - or - so increase in the climate sensitivity.