Emperor

If we are referring to ocean surface skin temperature, then yes it's measured by satellites, but any claim that an observed change is specifically due to back radiation (downwelling longwave from greenhouse gases) is an attribution step that depends on models, not a direct measurement of that causal component. The ~3 W/m² figure from Happer and van Wijngaarden (and the conventional ~3.7 W/m² value used in most assessments) is a calculated radiative forcing, not a quantity that will be measured directly as an isolated CO2 delta. We also would not be able to distinguish whether or not the additional changes were due to CO2 edge band increases or water vapor. Again, this figure assumes WV will increase by 1% per decade. So, in reality, doubling is exaggerated by both skeptics and "believers". For years, I would try to explain this, and people here would continue to confuse everything, trying to plug in algorithms in, not realizing that this is not a physics problem were the values remain consistent. All natural systems resist change and the earth pushes back for every change made. In chemistry pH resists change. A warmer surface emits more longwave radiation (the Planck response). Happer and van Wijngaarden emphasize the same point when they note that a ~3 W/m² clear-sky reduction in flux to space from doubled CO2 is only about 1% of the total outgoing longwave radiation, and that small changes in cloud cover or altitude can compensate for it. The system does not simply retain the extra energy because we can do math; temperature, water vapor, clouds, and circulation adjust until the top-of-atmosphere budget is restored. Or as I said, it pushes back in the Le Chatelier’s principle (Henri Louis Le Chatelier, 1884): "If the equilibrium of a system is disturbed by a change in one or more of the determining factors (as temperature, pressure, or concentration) the system tends to adjust itself to a new equilibrium by counteracting as far as possible the effect of the change.”