The importance of the oceans in global warming

The other day commenter ‘Gus’ set out an account of the role of the oceans on global warming that I thought was so good that I asked him whether or not I could publish it as a post, and he agreed. So here it is. It is not of course the whole story, but it is a neat summary of one aspect, and to the best of my knowledge it is factual where there are observations, and well-argued where one has to argue.

‘Ever since the end of the little Ice Age, the worst of which occurred during the times of Maunder and Dalton Minima, solar activity has picked up and continued on the increase throughout all of the 20th century, having reached the peak in the last two decades of it, whereupon it subsided. At its peak, the sun was at its most active in 9000 years.

What happens when the sun is active? There are two major effects. The first one is that the solar magnetosphere bloats, thus shielding the whole of the inner solar system from cosmic rays. As cosmic rays seed clouds upon entering the atmosphere (this is the same thing that happens in cloud chambers), there is less cloud formation during high solar activity periods. This is called Svensmark Effect, because Svensmark was the guy who drew physicists’ attention to this mechanism. It’s been since confirmed by experiments, some carried out by Svensmark himself, others by physicists at CERN, and the results published.

The second effect, also very important, is that during high activity periods, the sun actually gets a little darker, fancy that, this is because of sun spots. But the total energy emitted by the sun increases. How can this be? This is because the energy shifts to ultraviolet. What effect does this have on the Earth’s atmosphere and the ocean? It so happens, you see, that ultraviolet absorption by water is between eight and ten orders of magnitude stronger than absorption at visual wavelengths. So, this shift of solar energy to ultraviolet packs a real wallop of heat at the atmosphere, which is full of water vapor, and the ocean.

That this is so and that this is profound we know from countless observations that correlate solar activity periods with global climate and ocean responses. For example, ENSO is driven by the solar cycle. The flow of Parana river in South America and storminess over Brazil, are driven by the solar cycle. Algae blooms in the Mediterranean are driven by the solar cycle. The response is universal and very strong.

Now, what if you had a long period of subdued activity in the 17th, 18th and the early 19th centuries, followed by gradually increasing activity, to reach the highest activity in 9000 years in the last two decades of the 20th century? Of course, this would manifest, and has manifested, in globally increasing temperatures. They have been on the increase since roughly 1850 or so, and most of it, some 80%, has occurred prior to 1980. And, of course, it is not just the atmosphere that has warmed, the ocean has warmed as well, not from the atmosphere by from the direct absorption of solar UV and from diminished cloud cover. These two effects compound, you see.

Now, we invoke Henry’s law, which tells us how CO2 concentrations partition between water and atmosphere. The law is strongly temperature dependent: the warmer the water, the less CO2 water can hold, therefore as the ocean becomes warmer, it has to release excess of CO2, excess compared to the equilibrium at a given temperature, into the atmosphere. This is referred to as “ocean degassing.”

In summary: The increase in solar activity since 1850, with its peak in the last two decades of the 20th century, warmed the ocean and the atmosphere, in effect forcing the ocean to degas a part of its CO2 reservoir. This is a huge amount of CO2. According to current estimates, it accounts, together with soil degassing, for 97% of all observed CO2 emissions, leaving 3% only to human activities. Nearly all of the currently observed atmospheric CO2 concentration derives from the ocean and soils.

It is a godsend, because CO2 is a life giving gas: it is the foundation of the whole food chain of the earth bio-system. The more CO2 then, the more life on the planet’s surface. And we are seeing this too: in greening of the desert, in improved yields. If humans can contribute to this beneficial development by adding further 3%, so much the better.’

I feel the need to add only that the oceans cover more than 70 per cent of the Earth’s surface, and take up about 90 per cent of the energy received from the Sun. The oceans represent a heat sink of great size. It is entirely possible that the so-called ‘missing heat’ of the global warming paradox is concealed in the water somewhere, but we have no real way of measuring its size, especially in the abyssal depths.

But what we do know is that as water heats up its capacity to hold gases declines — Henry’s Law, above. It seems to me that the ‘degassing’ of the oceans over the past 150 years may account for a great deal of the increase in CO2 levels. If that is the case, the conventional AGW argument may well be a case of the cart before the horse.

Join the discussion 17 Comments

  • Peter Kemmis says:

    This is the most succinct statement that I have yet read, to explain the recent global warming and much of the rate of atmospheric carbon dioxide increase. While being aware of Svensmark’s work and its critical relevance, I had not realised the significance to heating of the ultra-violet band, that Gus explains here.

    With that ocean warming we have also thermal expansion, allied presumably with some loss of continental ice, to account for the steady rise in ocean levels. So the “missing heat” is not missing at all; while there is a lag (of some twenty years, perhaps) in thermal expansion, it may well be the case as we enter this next period of declining solar activity, that we see ocean levels also pausing in their rise, even in the next ten to twenty years. (I have heard comment that the rate of increase is already slowing, but others may provide substantiated advice on this.)

    • Gus says:

      The periodic return of ice ages is caused by the Milankovitch cycle. It has to do with the precession of the Earth’s orbit combined with nutation of the Earth’s spin and the current layout of the Earth’s continents. In short, there are times when the globe receives less solar energy, simply on account of the orbit’s geometry and the Earth’s tilt, which is when we end up with ice ages. Then, when the orbit repositions itself so that we receive more energy from the sun, the globe enters the interglacial, which is what we’re enjoying right now.

      The original theory proposed by Milankovitch, who worked on it while imprisoned in a POW camp during WWI, was refined by others and convincingly proven by measurements, see Hays, Imbrie and Shackleton in Science, 1976, doi:10.1126/science.194.4270.1121. More proof followed, as recently as 1999. There’s a paper by Rial who looks at variations in the isotopic composition of oxygen in the sediments at the bottom of the ocean, and finds that they correlate with orbital changes, Science, July 1999, doi:10.1126/science.285.5427.564.

      By now, Milankovitch theory is well accepted, but it was a long struggle. The theory was rejected by “the consensus” of Earth scientists, throughout the remainder of his life, he died in 1958. Only after his work was translated and published in 1969 by Israelis, it became the object of CLIMAP project, in the 1970s, which confirmed the theory. Later, in 1989, project SPECMAP delivered further confirmation of the Milankovitch theory, showing that the climate changes are responses to changes in solar radiation of each of the three astronomical cycles.

  • Hammy says:

    You have an excellent sense of humour, Gus. This is the funniest debunking of the denialist creed I have ever read. I can actually see the smirk on your face while you were writing it. Thanks Don for passing it on.

    • dlb says:

      I agree this post has issues, would you care to elaborate Hammy?

    • David says:

      You are confusing me. Gus is a denialist. Dont you mean to say “dubunking of the warmist creed”? Or am I missing something ? 🙂

      • Peter Kemmis says:

        Hi David
        Earlier this year I read of Svensmark’s work in Vahrenholt and Luning’s “The Neglected Sun”, and was quite struck by the explanation of further mechanisms for changing climate, beyond the Milankovitch cycles, and the longer term cycles such as Eddy’s 1000 year one. It seems to me to some extent, the sceptical literature has spent considerable effort in challenging the pro-AGW arguments on the grounds of climate history (as well as for other reasons, but I won’t digress there), but it is only more recently that very long term new mechanisms are becoming apparent.

        I am quite serious in my earlier comment, that an understanding of glacial and inter-glacial cycles, would contribute hugely to our understanding of periods of mere centuries, including from the Medieval Warm Period to today in 2014.

        So have you read Vahrenholt and Luning yet? I would appreciate your thoughts about the fundamental science – you can ignore what they say aout the climate debate itself! And here’s a reference that might make you smile:

        • David says:

          Hi Peter ,
          Thanks. I will have a look. I have next to no understanding of the science, as such. When I see an alternative explanation of warming, I want to see the data entered into a statistical model as an extra explantroy variable along side CO2. That will give me a sense of the relative importance of each variable. Its not the be all an end all to the debate, but it would be a first step.

          • Peter Kemmis says:

            Thanks, David. I’d be pretty confident you’d get the support of the authors and Svensmark’s co-operation for whatever access you need. I don’t know what there might be at this stage that you could use, because I think the focus has been on determining whether cosmic particles are actually one of the causes in aerosol creation. I don’t think there has been any quantification at this stage. But I believe you will find the science is worth reviewing. It is a bit of an advance on Arrhenius’ good work of nearly 120 years ago.

            As you see from my other comments, what strikes me (no pun intended) is that these effects could go quite some way in explaining much about climate. Perhaps what you could usefully investigate is the quality of work on statistical correlation of climate variations over the last 5000-10,000 years, with variations in our own solar activity. You could include in your analysis our knowledge of carbon dioxide levels over the same timescales. I know we have to rely so much on proxies, but I am generally encouraged that at least there seems to be agreement about much of that past climate history. (Maybe I’m wrong, and haven’t noticed the slings and arrows!)

            There are some Youtube presentations by Svensmark that you may find interesting – although the pace may be a bit slow for you.

      • dlb says:

        David, I took Hammy’s comment as sarcasm, I’d say he is in the opposite camp to Gus.

        • David says:

          🙂 Yes that thought crossed my mind afterwards. Sometimes I find it hard to pick up all the subtles in online blogging. 🙂

      • Gus says:

        I’m not a “denialist.” I do not deny science. I question warm-monger propaganda, which has about as much to do with science as Scientology.

        For more, peruse kindly Section TS6.1, “Key Uncertainties,” of IPCC WG1AR5 Report–I presume, this would be your climate Bible. Also see “American Physical Society Climate Change Statement Review, Workshop Framing Document,” December 20, 2013, for some insightful questions that the US physics community had asked their colleagues working in climate science.

        Last but not least, I would advise you to read the “US Senate Environment and Public Works Committee Minority Report–Critical Thinking on Climate Change, Empirical Evidence to Consider Before Taking Regulatory Action and Implementing Economic Policies,” September 4, 2014. There’s much food for thought in it.

        And then, ask yourself, if CAGW is true, how irresponsible of the Chinese, the Indians, Brazilians and the Russians, to turn their back on it and not even bother to attend the UN meeting? Do they know something you don’t?

  • dlb says:

    Gus, I agree the oceans are emitting CO2 but why are the surface concentrations of CO2 in the ocean increasing at 1.3 – 2.8 micro atmospheres per year?

    My guess is that any increase in oceanic CO2 emissions are more than offset by an increased uptake of CO2 due to higher partial pressures from anthropogenic emissions.

    • Gus says:

      There is no measurement that would demonstrate CO2 concentration in the sea water to be on the increase. All the talk about “acidification” is based exclusively on models with very little empirical substance behind it. When you measure ocean acidity close to the shore, you really measure the result of effluent, which is always occurring, with few notable exceptions, e.g., the Great Barrier Reef. The reason why the reef exists is the dryness of Australia and lack of such natural effluent in the form of major rivers that pollutes the sea water elsewhere (not necessarily man-pollute).

      The ocean acidity, and thus its CO2 content, is extremely hard to measure anyway: it varies from mile to mile, both horizontally and… vertically: it depends on the presence of algae, plankton, sea weeds, and other sea life, and floats with currents, both the surface ones and the deep ones. Our coverage of the ocean with direct probes is way too sparse to produce any trustworthy data, and acidity is not something you can measure from a satellite. What you can measure is the CO2 flux into and out of the ocean, which is what the Japanese GOSAT observes and what the US Carbon Observatory 2 will observe, the first data is expected next year.

      What GOSAT shows, for example, is that CO2 flows into the northern ocean in northern winter and then comes out of it during northern summer: this is very striking and confirms what you’d expect from Henry’s law. The slow growth of average atmospheric CO2 level is due to the tiny difference, which is yet to be measured, mind you, between the two oppositely directed fluxes that correspond to winter and summer: the GOSAT measurement isn’t precise enough. The difference would accumulate at times of high solar activity and would dissipate at times of below average solar activity.

      As to the ocean acidity itself, here’s something you can trust. The reconstructed pH history of Flinders Reef of the western Coral Sea, derived from “boron isotopic compositions in a ?300-year-old massive Porites coral” can be seen in doi:10.1126/science.1113692, Pelejero et al, Science, 2005. You will find a graph there that covers the last 300 years, and what the figure shows is that the pH varied between 8.17 and 7.9 in something like 6 major oscillations in that time, without an obvious trend, but in correlation with the Interdecadal Pacific Oscillation in roughly 50 year cycles. The reconstructed pH history of the South China Sea that goes 7000 years back shows large variation too with the measured sea pH 6000 years ago being lower than today, Liu et al, Geochimica et Cosmochimica Acta, 2009, doi:10.1016/j.gca.2008.11.034.

      Note as well that pH depends not only on concentration of acidic or basic substances in the sea water, but on the water’s temperature as well. In other words, you can vary pH just by varying temperature, assuming that you can somehow force the pH affecting substance to stay in water in unchanged concentration. The dependence is of the form of a constant term plus a term that is inversely proportional to temperature: this dependence is called “Nerstian Slope.” In summary: the higher the temperature of the sea, the lower its pH, quite regardless of any additional contribution by CO2 or other chemicals dissolved.

  • DaveW says:

    Hi all,
    Unless I’m totally confused (which does happen), all gases should follow Henry’s Law and if the oceans are warming and degassing some of the non-satanic gases should also be rising in their atmospheric concentration. Argon would seem to be the best test – it is non-reactive; we distill it out of the atmosphere for our use and seem unlikely to be affecting its concentration (some think all Argon is from the ancient Earth, so not being continually produced); and it is similar in concentration to CO2. Is anyone monitoring Argon to see if its dynamics are in flux? Oxygen and Nitrogen are parts of the biogeochemical cycles, and so would be less useful tests, but if there are any changes in them it would be interesting to know.

    • Gus says:

      Note that CO2 is a trace gas. There is only a tiny amount of it in the atmosphere, 0.04% at present (if it was to drop to below 0.015%, all life on earth would die, even at 0.022% slow-down in plant growth is noticeable). So, when the ocean degasses, it makes a big difference. On the other hand, oxygen, nitrogen and argon are present at roughly 21%, 78% and 1%. As most measurements are relative, it would be harder to detect any difference in the concentration of these major atmospheric gasses due to ocean outgassing. Note that all the “warming” between the end of the Little Ice Age and today has been a mere 0.7C. It’s barely measurable, if we can trust such estimates at all. In fact, we shouldn’t even think of it as “warming,” it’s more like “return to normal.”

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