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.