Climate cherry pickers: Falling humidity - 0 views
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Scientific skepticism requires we consider the full body of evidence before coming to conclusions. The antithesis of genuine skepticism is ignoring all the evidence that contradicts a desired conclusion.
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he article seems to overlook the relative importance of solar radiation and wind as being the two main drivers of evaporation, translating as the skin temperature of the evaporating surface rather than ambient temperature, and the airflow over it, which in the case of solar radiation would make water vapour more of a forcing than a feedback. This paper details the calculations and the various inputs that are involved BUREAU OF METEOROLOGY REFERENCE EVAPOTRANSPIRATION CALCULATIONS
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This doesn't seem like a particularly relevant or useful start to the discussion of this topic. John's done some nice work looking at humidity trends wrt the water vapor feedback, and it would be a shame to divert the discussion right from the start into a lot of wrangling over minutia.
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Ned, I feel it is both relevant and important enough to clarify given the statement in the article "Water vapor provides the most powerful feedback in the climate system. When surface temperature warms, this leads to an increase in atmospheric humidity." I feel that is not conveying a sense of the correct drivers that are most relevant to how water vapour enters the atmosphere in the first place. There is a need to be sure that the foundations any discussion is built upon are fully understood and solid.
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Johnd, are you suggesting that the most solar radiation is absorbed by the skin of the ocean, rather than by layers beneathe the surface? The citation you refer to is for calculating evapotranspiration on land, where light does not penetrate beneathe the "skin", at least not far. Water is actually fairly transparent to light so the very thin "skin" accounts for little of the absorbance, although eventually most incoming light is absorbed at depth. The skin temperature of the ocean (where the vast majority of evaporation on earth happens) is largely a function of mixed water column temperature as a whole, which reflects the balance between inputs (solar radiation, incoming IR radiation) and outputs (outgoing IR radiation, evaporation, convection, mixing)of heat energy. As the earth's temperature increases that heat balance results in higher mixed layer temps, which leads to high skin temps and greater evaporation.
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I also want to agree with Ned. This discussion of insolation and skin temperatures is a distraction. All other things being equal (insolation included), evaporation and water vapor should increase if the earth and atmosphere warm.