Okay. So the surface of the Earth undergoes evaporative cooling at a current rate of 86.4 W/m^2. According to Wentz et al.precipitation globally increased at a rate of ~1.4% per decade from 1987-2006. Evaporation = Precipitation-water balance condition. Implies a trend of 1.2096 W/m^2 additional evaporative cooling per decade. Simultaneous trend in the average of GISS (1200 km), HADCRUT4, and NCDC v3.2.0 was about .2 K per decade. Simple algebra, evaporative cooling per degree of warming: 6.048 W/m^2 K. Necessary temperature change for evaporative cooling to cancel decrease in radiative cooling by 3.7 W/m^2: ~.61 K.
Sanity check! Models increase evaporation at a rate of 1-3% per K. This translates to between 0.864 W/m^2 K and 2.592 W/m^2 K, assuming Earth-like baseline latent heat flux, which compensates 3.7 W/m^2 decrease in radiative cooling between ~4.4 to ~1.43 K. Models typically range in sensitivity between 1.5 to 4.5 K for a doubling of carbon dioxide. Okay, numbers check out-maybe slight underestimate? Ice albedo feedback?
Folding in other findings for maximum climate extremism:
Detrend average surface temperature index and UAH LT (over the same period) annual average anomalies. Quick regression, suggests amplification of short term fluctuations of 1.44 LT relative to surface. Divide LT anomalies by this factor. Trend over 1987-2006 is ~.12 K per decade. Simple algebra again: increase in evaporative cooling per degree of warming: 9.793 W/m^2 K. Sensitivity implied: ~.38 K per doubling.
Wow okay that’s pretty small. I can push it a little closer if I assume a smaller LT amplification factor (which is probably biased by GISS’s reduced interannual variability?)
Note this is a calculation of the feedback. If you want to get those numbers higher to the sensitivity you like, you can’t wave your arms around blathering like an idiot about “transient climate response.” Instead you need to wave your arms around blathering like marginally less of an idiot about “non linear feedback” or “time dependent feedback.” The current result indicates that there is a very high slope tangent to the curve of outgoing radiation as a function of temperature. Higher sensitivity requires this slope to drop off pretty rapidly. Just simple physics would suggest a baseline increase in the rate at 4σT^3-4σT0^3. You need some positive feedback that is relatively weak now but very strong at just a slightly higher temperature. Or I don’t know maybe you can appeal to ice sheet melting and carbon cycle feedbacks and we can agree that climate change could be a problem, you know, in a few hundred years. Certainly not this century.
Well, good luck with that.