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posted by martyb on Friday March 17 2017, @08:18AM   Printer-friendly
from the testable-predictions-==-science dept.

On May 1, 1967, Syukuro Manabe (真鍋淑郎) and Richard T. Wetherald published the landmark paper Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity (DOI: 10.1175/1520-0469(1967)024<0241:TEOTAW>2.0.CO;2) (URLs shortened because the odd characters in the URL seem to break the links), which was the first major attempt to model the earth's climate. Now, fifty years later, the science can be robustly evaluated, and they got almost everything exactly right. Ethan Siegel has an article (Javascript required) looking back at this first major attempt at global climate modelling and how well it has turned out:

The big advance of Manabe and Wetherald's work was to model not just the feedbacks but the interrelationships between the different components that contribute to the Earth's temperature. As the atmospheric contents change, so do both the absolute and relative humidity, which impacts cloud cover, water vapor content and cycling/convection of the atmosphere. What they found is that if you start with a stable initial state — roughly what Earth experienced for thousands of years prior to the start of the industrial revolution — you can tinker with one component (like CO2) and model how everything else evolves.

The title of their paper, Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity (full download for free here), describes their big advances: they were able to quantify the interrelationships between various contributing factors to the atmosphere, including temperature/humidity variations, and how that impacts the equilibrium temperature of Earth. Their major result, from 1967?

According to our estimate, a doubling of the CO2 content in the atmosphere has the effect of raising the temperature of the atmosphere (whose relative humidity is fixed) by about 2 °C.

What we've seen from the pre-industrial revolution until today matches that extremely well. We haven't doubled CO2, but we have increased it by about 50%. Temperatures, going back to the first measurements of accurate global temperatures in the 1880s, have increased by nearly (but not quite) 1 °C.

[Ed note: There seems to be an issue with the DOI link in that the URL itself contains both "<" and ">" characters. The actual URL is:

http://journals.ametsoc.org/doi/abs/10.1175/1520-0469%281967%29024%3C0241%3ATEOTAW%3E2.0.CO%3B2

If you are uncomfortable following the provided bitly link, just copy/paste this link into your browser. --martyb]


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  • (Score: 0) by Anonymous Coward on Friday March 17 2017, @08:55AM (5 children)

    by Anonymous Coward on Friday March 17 2017, @08:55AM (#480305)

    They say reducing albedo by 1% increases the temp by about 1°C in their model. Hmm, there doesnt seem to be good albedo or cloud cover data out there.

  • (Score: 0) by Anonymous Coward on Friday March 17 2017, @09:10AM (4 children)

    by Anonymous Coward on Friday March 17 2017, @09:10AM (#480309)

    We love our asphalt roads and shingles. We love our bricks and black cars. We love our windows, which look black as seen from outside.

    Yeah, that'll do it. :-(

    • (Score: 0) by Anonymous Coward on Friday March 17 2017, @09:30AM

      by Anonymous Coward on Friday March 17 2017, @09:30AM (#480315)

      While that effect certainly exists, I am skeptical it can amount to a 1% change. I'd like to see good historical data on cloud cover near the equator, especially over the (low albedo) oceans.

    • (Score: 2) by ledow on Friday March 17 2017, @01:18PM (2 children)

      by ledow (5567) on Friday March 17 2017, @01:18PM (#480377) Homepage

      2/3rds of the Earth surface is water.

      Now we're down to 33%

      Of that, the human visible roads and cities visible from outer space = 0.

      In fact, according to certain papers I just googled, only 2.7% of the world's land is urbanised.

      You're now down to 0.9% of the Earth already.

      How much of that urbanisation affects the albedo, isn't cancelled out by local factors etc? Seems like it might JUST touch 1%, but chances are the albedo effects would be less than 1%.

      Especially when you consider that the solar energy is only on half the planet at the time. So we're down to 0.5% really.

      • (Score: 2) by HiThere on Friday March 17 2017, @04:05PM (1 child)

        by HiThere (866) Subscriber Badge on Friday March 17 2017, @04:05PM (#480470) Journal

        When you're measuring albedo you need to consider that dirty snow reflects less light than white snow, and that ocean water reflects less light than ice. Etc.

        Another thing is that just because you can't see a change from space doesn't mean it has no effect on reflected light. People are only sensitive to the amount of light available when they are doing a direct comparison. A comparison with a remembered observation is *quite* unreliable. To show this, watch a really bright movie, and then leave quickly for outdoors on a dim day. The movie was seen as bright, but when you go outside your pupils contract.

        The thing that bothers me is that I would expect the change in albedo to be much more than 1%, but perhaps increasing desertification has upped the albedo in some regions.

        --
        Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
        • (Score: 0) by Anonymous Coward on Friday March 17 2017, @06:04PM

          by Anonymous Coward on Friday March 17 2017, @06:04PM (#480526)

          It isn't linear either.
          Reduced albedo of snow has much less effect because snow tends to happen where sunlight is least dense due to the tilt of earth's axis, aka "winter."