Albedo, and its role in ‘climate change’

The word ‘albedo’, like the word ‘albino’, comes from the Latin word for white — albus. Actually, we get ‘albino’ directly from the Portugese, who used it to refer to what they saw as ‘white’ African negroes, whose skin lacked the black pigment. In astronomy, albedo refers to the amount of sunlight that is reflected from an object. It is commonly expressed as a number from 0.0 to 1.0 that measures the fraction of solar radiation that is reflected from the object’s surface. Earth has an albedo of 0.29, which means that about 29 per cent of the sunlight is reflected from its surface.

That 29 per cent is an average, of course. The North and South poles do much of the reflecting, while the tropics absorb the most. You can see that in the accompanying diagram.


The Antarctic reflects more two thirds of the sunlight that approaches it, while the tropics reflect less than a quarter.

I owe much this knowledge to an intriguing essay by Willis Eschenbach on WUWT. Eschenbach has claims to be one of climate science’s chief ‘citizen scientists’, because he writes such a lot, his work is always accessible, at least in part (his mathematics are far more advanced than mine), and it is relevant.

What is it relevant to, in this case? Ah, Mr Eschenbach is interested in an old question. Can the seas actually boil? Somewhere he has written, and I have referred to it, his contention that there is a highest temperature in the oceans, and it is about 30 degrees C. Why is that important? Well, one of the dooms awaiting us, from the AGW scaremongers, is that the seas will not only rise up in height, but rise up in temperature as well, killing all sea life, and in turn us as seafood-eaters.

There seems no evidence of such an event in the past, and Eschenbach argues that there must be some kind of thermostat or governor in the ocean-atmosphere system that prevents the seas just getting hotter and hotter. And in the WUWT article that I have mentioned he uses some fancy mathematics to argue that there is such a governor: as the tropical seas warm up, it seems that beyond a certain temperature (about 26 degrees C) the outcome is increased albedo. In short, as things get hotter, so the system acts to cool it down.

This contention caught the interest of a systems engineer, Dave Burton, who wrote as follows (a bit of editing only):

With my background in Systems Science, I see feedback mechanisms everywhere. One develops a nose for them, and, in the natural world, as in engineering, most of them seem to be negative (stabilizing) mechanisms, which attenuate forcings.

You seem to have identified a non-obvious but doubtless very important negative (stabilizing) feedback mechanism, Willis.

There are many other negative feedback mechanisms at work, too. Some of them are obvious, others less so.

1. Most basically, of course, the warmer things get, the faster they lose heat. But, also:

2. As temperatures go up, evaporation at the surface increases. That removes “heat of evaporation” from the surface. Moist air is lighter than dry air (contrary to intuition), so the moist air rises until the moisture condenses into water droplets or ice flecks, as clouds, releasing the latent heat which was absorbed at the surface. Thus the water cycle is a classic phase-change refrigeration cycle, removing heat from the surface, and releasing it aloft, just as the Freon phase-change refrigeration cycle cools your refrigerator.

Anything which increases surface evaporation (such as warmer water, or reduced ice cover) increases water-cycle cooling.

Because increase surface temperatures make the cycle run faster, it is a negative feedback mechanism, cooling the surface faster, as temperatures go up.

3. As levels of The Precious Air Fertilizer (CO2) levels go up, so do plant growth rates. That removes more CO2 from the air, attenuating the increase in CO2 — another negative feedback mechanism.

4. At extreme latitudes, warmer water reduces ice cover. That increases evaporation, making the water cycle run faster, and cooling the water (#2, above). It also allows wave action to create turbulence beneath the surface, allowing faster exchange between water at the surface (cooled by evaporation) and water beneath the surface, thereby helping to cool the water.

5. The additional evaporation due to more open water also apparently causes additional cloud cover, increasing albedo at altitude, and additional lake-effect/ocean-effect snowfall downwind. Some of that snow falls on the ice-sheets, increasing ice accumulation, and some of it falls on land, increasing albedo, decreasing land temperatures, and prolonging winter — another negative (stabilizing) feedback mechanism, by which additional warmth causes additional cooling.

Note: that snow accumulation is a big deal. The magnitude of ice accretion from snowfall on ice sheets was illustrated by the team which salvaged Glacier Girl from under 268 feet(!!) of accumulated ice, 50 years after she landed on the Greenland ice sheet.

But the negative feedback mechanism you’ve identified, Willis, is new to me. Very excellent work!

And the last reference caught my attention, because I too wrote about Glacier Girl (here). It still shocks me that no one who writes anxiously about the melting of the Greenland ice-cap has bothered to ponder over the fact that in fifty years the Greenland ice cap, or at last a part of it, added more than 85 metres of ice through snowfalls.

Dave Burton’s comment really is thought-provoking. I too am conscious of negative feedbacks, but I can’t prove them. What we do, really, is to say that if there are  positive feedbacks, and they are a threat, then there ought to have been some kind of incident or event in the prehistoric past that we can point to as an illustration of what might happen today. To the best of my knowledge, there isn’t one. Again, it seems that systems that attain an equilibrium of some kind contain forces that tend, other things being equal, to return the system to equilibrium if there is a disturbance to it.

It doesn’t mean that there aren’t positive feedbacks. But with respect to climate, there don’t seem to have been positive feedbacks that last for very long. And if there are demurs from the orthodox, it would be useful to be provided with examples.

Join the discussion 20 Comments

  • dlb says:

    If people are honest there is an underlying belief which draws them to the view they take in the climate debate. Some may have a faith in authority, for others it is what that conforms with their political or world view, and then some may just be naturally sceptical or cynical. Real world evidence is only secondary to this gut feeling.

    For me it is this idea of negative feedback that makes me a climate sceptic. I just can’t believe that the earth has been around for so long supporting life without negative feedbacks. In nature, systems such as our body are stable because of such feedbacks. I am also somewhat sympathetic to Lovelock’s Gaia hypothesis that the earth is analogous to a living organism in that it self regulates, not consciously of course.

    Dave Burton and Willis E. give examples of such feedbacks and we also have the ocean which is one giant shock absorber. If I had to bet on it, I would say AGW would be lukewarm at worst.

  • Alan Gould says:

    Once again, Don, thanks for this helpful and lucid account of albedo and the dynamism of feedbacks. It is exactly what I joined the group to learn.
    My problem lies in being able to remember it all when in exchanges with the alarmists. I have a brain that can remember all the monarchs of England back to Alfred, and hundreds of lines of poetry, but will forget what a zygote or an enzyme is 5 minutes after being told. Anyway, I now know more after this elucidation of Earth’s libido effect…..See what I mean!

  • David says:

    Eschenbach argues “The warmer the ocean gets, the lower the albedo goes, a negative correlation … except when the temperature gets over about 26°.” That may be correct.

    But the average temperature of the ocean is about 15-17 degrees! Ocean temperatures of 26 degrees only occur in the tropics. We can’t just allow ocean temperatures to reach 26,degrees on the basis that some negative feedback on the albedo will begin to kick in. That is hardly much cause for complacency.

    • dlb says:

      Good point David. Below is a possible rebuttal from Eschenbach’s WUWT thread. A bit of discussion followed but no conclusion seemed to be reached mainly due to the lack of recent research in the area.
      Rob JM says:
      June 4, 2015 at 5:54 am
      “You are forgetting that high latitude areas radiate more energy than they absorb from sunlight. The increased cooling at night time (due to lack of cloud) may outweigh the increased warming in daytime.”

    • Don Aitkin says:

      David, is it possible that you have in mind the world according to Mercator? A knowledgeable friend has written to me to point out that ‘50% of the Earth’s surface lies between 30N and 30S, i.e. in the tropical belt, so what happens in this band can have a big impact on the average global temperature anomaly. (For what it’s worth, 38.4% lies between 30 and 60 deg latitude and 11.6% lies between 60 and 90.) Don’t be fooled by the maps drawn with Mercator’s projection that imply equality. As an example, if temperatures didn’t change in other bands but rose by 1 degree in the 60 to 90 band, the change in global average would be 0.116C but if the increase was 1 degree in the tropics the global average would rise 0.5C. The temperature consequences of any change in cloud cover need to take this into account.

      • dlb says:

        Ah Mercator, definitely a flat earther if ever I heard one.

      • David says:

        I just Goggled it and got 17 degrees. Do you have an alternative estimate ?

        • Don Aitkin says:

          David, what is the point of your estimate? What Willis E is talking about is a feedback mechanism that he argues operates when the sea temperature rises above 26 degrees C, which it does only in the tropics. Above that point, he suggests, albedo kicks in to cool the planet by reflecting more solar energy.

          Yes, the average ocean temperature seems to be around 15 to 17 degrees C. And this means, in terms of the Eschenbach argument, exactly what?

          • David says:

            That the “average” piece of ocean can undergo a 9 degree (26-17 =9) increase in temperature before these feedback process will begin to begin to kick in.

          • dlb says:

            The dewpoint is much lower outside the tropics. Have you ever seen fog sitting over a lake in the winter? I’m sure the lake surface would be well below 15c.
            Increase in cloud with slight ocean warming would certainly be possible over temperate regions. The thing is cloud may well be a positive feedback in these higher latitudes.

          • David says:

            What you are trying to say?

            You look like you are clutching at straws!

          • dlb says:

            Oceans in temperate regions are not going to get anywhere near 26 deg from whatever forcing, there is simply not enough energy in the system. It would be reasonable to think that any increase in oceanic temperatures in higher latitudes would produce more cloud, increasing min temperatures and decreasing max temperatures. Think the Gulf Stream.
            Like Mr Eschenbach this is just my reasoned opinion, I would be most interested to hear expert opinion

          • David says:

            But that’s NOT what Eschenbach argues, he wrote.

            “The warmer the ocean gets, the lower the albedo goes, a negative correlation … except when the temperature gets over about 26°.”

            i.e. in places with a water temperature less than 26 degrees, increased temperature LOWERS the albedo. You are arguing at these higher latitudes that there will be more cloud cover (aka MORE albedo).

            So send him an email and tell him what you think is “reasonable”.

            But I do agree with you when you say that average ocean temperature will not rise to 26 degrees ie 9 degree increase. But the AGW concern is that average temperatures increases in the range of 2 to 3 degrees would be highly problematic.

          • Don Aitkin says:

            I’m lost. The tropics have the hot seas and are the ones where the albedo issue is important. The polar seas have very low temperatures indeed, and the ‘average piece of ocean’ is simply a statistical construct. WE is talking about the tropical seas, the ones where the thunderstorms occur.

          • David says:

            and you wonder why the ABC wont invite you on as an “expert” 🙂

            Look,whats his name is trying to dispel AGW with some reference the albedo.

            “Well, one of the dooms awaiting us, from the AGW scaremongers, is that the seas will not only rise up in height, but rise up in temperature as well, killing all sea life, and in turn us as seafood-eaters.” (this is BS but I will let it slide )

            But 26 degrees is too hot. Most of the world ocean is way less than 26 degrees, on average 9 degrees less. So yes there may be a cap of 26 in the tropics but what about the rest of the planet?

          • Don Aitkin says:

            I agree with dub in his second comment below.

          • David says:

            I like dlb, but he is not going to be invited by the ABC to talk about AGW, either. None of us (myself included) are experts on this topic. 🙂

          • dlb says:

            The ABC won’t even publish any of my humorous quips at “The Drum”. Bunch of so and sos 🙂

  • JMO says:

    I shudder at all the black roofs on new houses in the new ‘burbs’ and also on some renovated older houses. Black roofs absorb so much more heat from the sun, increase urban heat island effect and decrease the planet’s albedo, but they are trendy, along with black cars.

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