Humidity And Temperature

The US is cold right now, largely due to very dry air. Note that dew points are below 0C across almost the entire country. This has two effects – it reduces the greenhouse effect, and reduces the amount of heat being generated from condensation.


Now compare vs. Saudi Arabia, which has much higher humidity with dew points in the 10-20 C range.

imagefetch (2)

And Australia which has dew points in the 10-30C range.

imagefetch (1)Middle East Weather Map – Current Dew Points of the Middle East – Find Local Weather

Also note that reduced temperature further reduces the amount of longwave radiation being generated by greenhouse gases in the atmosphere.

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38 Responses to Humidity And Temperature

  1. richard says:

    it’s interesting . as noted on another site.

    “Sub-freezing temps in the 30°N range?”- in the US

    “That’s the same latitude as northern Africa!”

  2. richard says:

    comparing North Africa to the US Humidity wise. Though of course the dew points are different.

  3. David says:

    Is there a point where humidity is essentially the only GHG? I don’t mean the only but essentially all others don’t contribute enough to worry about.

  4. A couple of years ago I published a paper on that showed the moderating effect of humidity on temperature. The paper can be found as a pdf at . In this paper I compiled 2 years of data showing the relationship of both relative and absolute humidity and daily temperature in two different locations on the continent of Africa. In this paper I demonstrated that the correlation of humidity and temperature is clearly negative.

    • Humidity increases nighttime temperatures.

      • Dr. Daniel M. Sweger says:

        I agree, and for the same reason that during the day high humidity slows the increase in temperature. The reason is that heat energy only flows in one direction: from a higher to a lower temperature. It is the same as in an electrical circuit. Electricity only flows from a higher potential to a lower one. During the day the energy from the sun is flowing from the sun towards the surface of the earth. The high specific heat of water impedes the flow of heat in the same way as a higher value of a resistor impedes the flow of electrons. At night the situation is reversed. Now the heat energy is flowing away from the earth into a very cold space, and the presence of water vapor impedes the flow of heat energy away from the earth’s surface. Thus the surface temperature decreases less on a humid night than a dry night.
        The purpose of the paper was to demonstrate that any feedback loop between the effect of “greenhouse gases” and the earth’s surface must be negative, since it would result in an increase in water vapor, and thus an increase in the impedance of heat flow..

      • Mack says:

        “Humidity increases nighttime temperatures” It doesn’t actually increase the nighttime temperatures Steve, but makes them warmer than they otherwise would be without the humidity. Daniel M Sweger has got the handle of it.

        • I’m not interested in having this same stupid conversation 10,000 times, thanks.

        • Mack says:

          Well, all I can say Steve is that I’ve never heard of the temperatures going up when the sun goes down.

        • I’m not interested in having this same stupid conversation 10,001 times, thanks.

        • Gail Combs says:

          Mack says: “Well, all I can say Steve is that I’ve never heard of the temperatures going up when the sun goes down.”
          Then you have not paid much attention to the weather because it happens. It is called a warm front and some times the warm wind comes in after the sun sets.

  5. Baa Humbug says:

    Correlation and causation.

    • squid2112 says:

      Dryness causes cold .. apparently .. so this has nothing to do with the cold air moving down from the polar regions, it is the “dry” air that done it. If we just remove water from the tropics, they will freeze. Elementary …

      • Gail Combs says:

        Squid, If you remove the Sun+ Water then you freeze.

        For May 2012, Barcelos, Brazil (Lat: 1 South)
        Temp: monthly min 20C, monthly max 33C, monthly average 26C
        Average humidity 90%

        For May 2012, Adrar, Algeria (Lat: 27 North)
        Temp: monthly min 9C monthly max 44C, monthly average 30C
        Average humidity around 0%

        Water vapor moderates the temperatures. The Dust Bowl era in the USA as Steve recently showed had very high temps in the summer but also had very low temps in the winter.

        Cold Arctic air coming down from the north is going to warm up and also become dryer unless it mets tropical air being sucked up towards the Arctic by the Jet Stream at which point we really get dumped on. (Hopefully with a bullseye painted on DC)

    • Yes, you have to understand the basic physics mechanisms to understand the causative agent and what its results are. Cold, dry air sweeping down into the American plains states will cause the temperatures to drop, but so would cold, wet air do the same, if air from the arctic were somehow to be wet.

      • The reason the Arctic is so cold is because it is dry air.

        • Gail Combs says:

          Are you sure Steve? It is an ocean unlike the Antarctic.

          I did a quicky look at places within the Arctic circle:
          Barrow, AK
          16th – Humidity 100%
          17th – 96%
          Now – 95%

          Murmansk, Russia – 87%
          Tromsø, Norway – 87%
          Rovaniemi, Finland – 99%
          Sisimiut, Greenland forecast 73% (Not reporting now)

        • You are confusing relative humidity with absolute humidity. Cold dry air is often close to 100% relative humidity.

        • Gail Combs says:

          OOPs you are correct. That is what I get for posting when the brain is half asleep but at least it clears up the point for the silent peanut gallery.

        • Gail Combs says:

          Another quick look
          Mid North Carolina: – 12 °F – Humidity: 89%

          Barrow, AK 15.3 °F – Humidity: 92% (Light Snow Blowing)
          Murmansk, Russia 32 °F – Humidity: 87% ( Mostly Cloudy)
          Tromsø, Norway – 43 °F – Humidity: 87% (Mostly Cloudy)
          Rovaniemi, Finland – 26.6 °F – Humidity: 99% (Freezing Fog)
          Sisimiut, Greenland – Not reporting

          It really sucks when it is colder in North Carolina than it is around the Arctic Circle.

          Displaced southern air from the wandering Jet stream?

          Gulf Stream?

          Maybe time to ask Dr. Gray or Joe Bastardi.

  6. Warren Walker says:

    Your post: “Also note that reduced temperature further reduces the amount of longwave radiation being generated by greenhouse gases in the atmosphere.”
    I though Greenhouse asses emitted shortwave radiation.

  7. PJ London says:

    Couldn’t possibly be because the winds in N America are coming from the north /west and crossing the Arctic and Rockies (elevation) , and the winds in Saudi are coming from the west and crossing the Sahara (effectively zero elevation).
    In Kuwait when the wind is from the south or east it is cool and when from the west B* hot.

  8. Rob says:

    Quick question, when you said “Also note that reduced temperature further reduces the amount of longwave radiation being generated by greenhouse gases in the atmosphere.”

    I presume by “longwave radiation being generated by greenhouse gases” you mean “longwave radiation heat being generated”?

  9. Anto says:

    I predict that Gavin will declare November 2014 to be the hottest on record for the USA.

  10. Hans Conser says:

    It is simple to understand, cloudy days are cooler, cloudy nights are cooler, and clearly this effect is much much stronger than CO2

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