Maggie's Farm

Quite the conspiracy, especially considering that the scientific basis of the atmospheric greenhouse effect dates to the 19th century. See Arrhenius, On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground, London, Philosophical Magazine and Journal of Science 1896. Indeed, without the greenhouse effect, the Earth’s surface temperature would average a chilly ≈-18°C rather than the balmy ≈+15°C that it is.

nh4kx3: But the belief in catastrophic warming rests in large part with James Hansen and his first models.

The relationship between atmospheric carbon dioxide and water vapor (climate sensitivity) was established more than a century ago. Arrhenius calculated (1906) climate sensitivity at about 4°C per doubling of atmospheric carbon dioxide, which was not too far from the modern value of 2-4°C. Furthermore, positing a climate sensitivity much below 1.5°C is contradicted by paleoclimatology; in particular, the oscillation of the Earth from icy periods to ice-free periods.

nh4kx3: Drying alone only allows evaporation, it does not force it.

Assume you are referring to when CO2 increases, the atmosphere can hold additional water vapor. You seem to forget that the Earth is a watery world, so the amount of atmospheric water vapor is largely determined by ambient temperature, not the availability of water (unlike an ordinary human domicile where, as the temperature increases, the amount of water vapor in the air remains constant, so the relative humidity decreases). On the other hand, increase the surface temperature of the Earth, and atmospheric water vapor will increase (and conversely). So, yes. An increase in Earth's surface temperature will cause an increase of atmospheric water vapor.

But you might say, that is just a hypothesis—which is why scientists have built and launched satellites to make observations of atmospheric water vapor. These observations show that the Earth's atmosphere is moistening, a sign and degree (+7% per +1°C) consistent with the hypothesis, and contradictory to your position.

And, again, positing a climate sensitivity much below 1.5°C is contradicted by paleoclimatology.

nh4kx3: The question is, can warmer air alone cause increased evaporation. I say it cannot since increased evaporation will reduce surface temperature, and that sea surface temperature is the variable that controls column water.

Yes, evaporation absorbs heat as the system seeks equilibrium, but the equilibrium will be at a higher temperature.

Observation trumps every time. The surface, including the ocean surface, is warming and the atmosphere is moistening consistent with predictions.