Increasing Water Vapour Should Increase Atmospheric Pressure

If there really are more molecules of H2O in the atmosphere than there used to be, that would mean that the total weight of the atmosphere is greater than it used to be – even if the density is lower. More total weight means higher average atmospheric pressure.

I have been doing some investigation of this and have found no evidence so far to support an increase in atmospheric pressure. Is anyone aware of any studies on this subject?


About stevengoddard

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22 Responses to Increasing Water Vapour Should Increase Atmospheric Pressure

  1. Fred Harwood says:

    Might an increase in H20 in the troposphere also increase its average height?

  2. Latitude says:

    Steven, I posted a several links that might help….barometric pressure charts
    check moderation hell….

  3. John B., M.D. says:

    If there is an effect, it would be tiny and negligible compared to numerous other factors, and probably not measurable given the signal-to-noise ratio. I have no idea if there are studies, and if there were atmospheric pressure readings across the globe for many years. My guess is that the accuracy of the pressure sensors over the years would be poorer than that of simple thermometers, and that the data would be useless (even moreso than the corrupted incomplete repeatedly-adjusted temp record).
    The simple observations that baseball flight distance depends mostly on velocity off the bat, ball spin (thus altering the trajectory), altitude (e.g. you don’t want to be a pitcher in Denver), wind direction and speed, relative humidity, absolute temperature, in no particular order.

    • There is very accurate barometric pressure data going back at least 60 years. A 10% increase in H2O would be very noticeable.

      • John B., M.D. says:

        So would a 10% increase in temperature (and I’m talking Kelvin).
        What is the purported increase in the amount of water vapor in the air (conservative and alarmist estimates)? Given the tiny temp increase over the 60 years, is the increase in water vapor that much? I don’t know.
        This seems to be an interesting thought experiment.

      • John B., M.D. says:

        I meant a 10% increase in temp would be noticable, as compared to the 1 degree magnitude claimed by AGW alarmists.

      • vapcguy says:

        Temperature is a factor in the ideal gas equation –> (P1*V1)/T1 = (P2*V2)/T2. There is a direct relationship that as temperature goes up, within a closed-in area, since the volume is constant, pressure must also go up. We could debate whether the atmosphere is “closed-in”, since it is open to space, but it does have a limit of area of only so far as the earth’s gravity extends… but I wouldn’t know how much atmospheric pressure is needed to overcome that gravity.

  4. PajamaMan says:

    As I pilot I recall we were taught that dry air is denser than moist air. Dry air most definitely provides better lift than moist air. The primary constituents of the atmosphere, nitrogen molecules (which are composed of two nitrogen atoms) and oxygen molecules (composed of two oxygen atoms), are both heavier than water molecules. So an increase in water vapor will, counterintuitively, result in a decrease in absolute pressure.

    • The density decreases, but an overall increase in H20 would cause the thickness of the atmosphere and the average pressure to increase. With lighter molecules you need more pressure to achieve the same density.

    • Robertvdl says:

      So during the cold part of the ice age with sea level 120m lower and most of the moisture locked up in land ice and more dust in the air , atmospheric pressure at sea level in the tropics would be higher.

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