I have been asking “Where’s the control system theory in all this?” It’s an equilibrium seeking system subject to the math of feedback controls.
My opinion is the climate models are just in the appetizer stage, the main course straight thinking on this matter is still out there in the kitchen .
You are more on track than the rest i’ve seen.

And your points about water vapor are right on target.
Please see my tweak of the ocean heat guys a couple years ago,
comment #96 on this ocean heat content blog,
http://www.realclimate.org/index.php/archives/2006/08/ocean-heat-content-latest-numbers/comment-page-2/#comments

I believe the regulating mechanism you seek lies in the slope of the saturation pressure curve for water.
Given that our atmosphere has a particular weight hence a particular pressure, there exists a temperature around which the vapor pressure of water will affect the thermodynamics of air with maximum effect. That is, it will make density of air change more than it would from temperature alone, and even more significantly will optimally affect its specific heat as a working fluid in your heat engine. Mother nature loves a balance!

Were i forty years younger i’d try to calculate it for you.

I spent a lifetime fixing feedback control based regulating systems and am fascinated by the math involved. See any text on Modern Control Systems.
That math was discovered by Descartes but set aside as an interesting curiosity. Well, that is until WW2 when the German scientists found it’d make their rockets work. The German texts were brought back as a war prize along with Dr Von Braun who explained them to our guys.
But i digress.

Anyhow – if i can find my steam tables and Dad’s old “Climate and Man” textbook i might try to horse out some simple approximations …

meantime, i applaud you as the first climate guy to put Descarte before the hors d’ouvres.

Sincerely, old jim hardy

An analysis of the Vostok data gives the following relationship:

T0 – T1 = 14 log(C0/C1,2), r^2 = 0.66

where T0-T1 is the temperature change (°C), and C0/C1 is the ratio of the starting and ending CO2 levels (ppmv).

This has two consequences. First, it indicates that the change in temperature in the 20th century is not the cause of the current rise in CO2. If the Vostok data is correct, a 0.6°C temperature rise would only raise CO2 by about 10 ppmv.

Of more import to the present discussion is that if CO2 is driving temperature, according to the Vostok cores a change in CO2 from 280 ppmv to 380 ppmv should have resulted in a 6°C temperature rise.

Obviously this hasn’t happened … and the question is, why not? I believe that my thermostat hypothesis explains why not, although certainly there may be other explanations.

Things like the PDO only seem to temporarily alter some aspects the large scale flow of the ‘conveyor belt’, such as dragging up more deep water along the west coast of South America than normal. This does not currently change the actual circulation system in any major way. What is not know is if significant climatic changes could flip the whole circulation pattern from one state to another.

Since the PDO lasts on the order of thirty years or so, I’m not sure what you are calling “temporarily”. Also, we don’t yet understand what drives the PDO, or what actually changes during the PDO. So I would doubt very much that we can state that the PDO “does not currently change the actual circulation system in any major way”. Seems like a bridge too far.

It’s not an either/or of “pushing towards a tipping point” vs “pushing away from a tipping point”. There are likely to be many tipping points, and pushing away from one may push towards another at the same time. Yes, if forced to chose, I’d probably rather live in a Greenhouse world than in a Snowball world, but in reality, I prefer a nice interglacial.

My point was simple. We don’t know what a tipping point looks like. We can’t identify them in past climates, other than to note that some climate changes occur fairly quickly … but that tells us simply that some particular threshold was exceeded. It does not, however, tell us anything about what that tipping point was.

Myself, I find the discussion of “tipping points” generally to be a lot of handwaving. Yes, they might exist … but since we don’t have a clue what they look like even if we were to see one, what good does the entire “tipping points” discussion do? People rave on about how we’re going towards some “tipping point”, but when push comes to shove, they can’t say what a tipping point might look like if it hit them in the face.

w.

1. During part of the year, water is freezing. This leaves behind a heavier liquid, which tends to sink. This helps the thermally driven current that moves towards the equator.

2. During another part of the year, ice is thawing. This leaves behind a lighter liquid, which tends to float. This hinders the thermally driven current that moves towards the equator.

w.

I don’t have access to the actual Nature article, so I’ll address the popular press summary (ugh!): It appears that the floats they used to measure the Deep Western Boundary Current (DWBC) only reached a maximum depth of 1500m. At that shallow depth I would expect there to still be some influence by the Gulf Stream. Considering that the ocean basins are generally deeper than 2000m, and on average 3-4000m, I would expect the main flow of the DWBC to occur at those depths.

I agree, ocean currents are anything but simple lines (we always try to spot the circulation maps that have the major current arrow going right across New Zealand). The details don’t change the fact that there is a major ocean circulation system the governs the movement of water in the oceans, and along with it energy.

Things like the PDO only seem to temporarily alter some aspects the large scale flow of the ‘conveyor belt’, such as dragging up more deep water along the west coast of South America than normal. This does not currently change the actual circulation system in any major way. What is not know is if significant climatic changes could flip the whole circulation pattern from one state to another.

It’s not an either/or of “pushing towards a tipping point” vs “pushing away from a tipping point”. There are likely to be many tipping points, and pushing away from one may push towards another at the same time. Yes, if forced to chose, I’d probably rather live in a Greenhouse world than in a Snowball world, but in reality, I prefer a nice interglacial.

And if you don’t like the idea that Thermohaline circulation is largely driven by polar ice, you’re a lone voice. But by the way you describe the process, I take it you haven’t actually understood it. Deep water creation at the poles is huge (check the figures I stated). Thawing in summer doesn’t warm the waters (physics of phase transitions) and enough ice remains (yet) to maintain the system. There is certainly not “no net effect”.

Warming waters at low latitudes create a weak enough flow to be overwhelmed by other factors such as winds and upwelling of deep sea currents. As you point out in the salinity chart you link to, in the current state the tropics are unable to affect the current as a driver because of the strong and continuous flow of very cold deep waters. However, should these deep waters weaken, and at some point even warm up, then it’s possible that the evaporative driver could become significant. But as I said, Halothermal circulation is several orders of magnitude weaker than Thermohaline – you could probably kiss the fishing industry goodbye.

Next time, if it disappears I’ll just wait.

Thanks for providing the venue for what has turned out to be a most interesting discussion.

w.

Went to bed, and when I got up, both were there … go figure.

w.

REPLY: Posts with a lot of words + URLs tend to get put in the spam filter, we regularly rescue them – Anthony

From Science News

Cold Water Ocean Circulation Doesn’t Work As Expected
ScienceDaily (May 14, 2009) — The familiar model of Atlantic ocean currents that shows a discrete “conveyor belt” of deep, cold water flowing southward from the Labrador Sea is probably all wet.

New research led by Duke University and the Woods Hole Oceanographic Institution relied on an armada of sophisticated floats to show that much of this water, originating in the sea between Newfoundland and Greenland, is diverted generally eastward by the time it flows as far south as Massachusetts. From there it disburses to the depths in complex ways that are difficult to follow.

A 50-year-old model of ocean currents had shown this southbound subsurface flow of cold water forming a continuous loop with the familiar northbound flow of warm water on the surface, called the Gulf Stream.

“Everybody always thought this deep flow operated like a conveyor belt, but what we are saying is that concept doesn’t hold anymore,” said Duke oceanographer Susan Lozier. “So it’s going to be more difficult to measure these climate change signals in the deep ocean.”

And since cold Labrador seawater is thought to influence and perhaps moderate human-caused climate change, this finding may affect the work of global warming forecasters.

Original study is subscription, abstract here

Given that our understanding of what the oceanic currents do now is obviously incomplete, our understanding of currents in the past must necessarily be poorer than that of today. As the study shows, the ocean currents are not the simple lines we like to draw on charts. They are complex networks that shift location and speed and direction on scales from minutes to months to millennia.

So you are correct to identify the changes in the continents, particularly opening and closing gaps between islands and continents, as being crucial to the setting of the global thermostat. And certainly we know, from drill cores and sediment beds and the like, that a current flowed here 1.5 million years ago, and there 3.7 million years ago, and in a third place 4.6 million years ago. However, determining where the currents flowed a million years ago on anything resembling a global scale when we don’t know where they flow today is a bit of a stretch.

On a shorter timescale, things like the PDO indicate that there is more than one “quasi-stable” pattern in which the oceanic currents can flow. But what flips the PDO from one state to the other? We haven’t a clue.

Regarding the concern you expressed at the end:

But the big unknown is, what whould happen if humans manage to influence the climate enough to weaken to HT system. Climate systems appear to often switch abruptly, and we don’t know if the current climate system is robust enough to ignore what we’re doing to it.

The changes that humans have made to the surface of the earth are likely to have warmed it. Chop down the trees and you chop down the clouds. More sun plus less moisture means greatly enhanced surface heating (more heating plus less evaporative cooling).

But I’d say that “are we pushing the climate away from a tipping point” is as valid as “are we pushing the climate towards a tipping point”. Since we have no knowledge or definition of what might constitute a tipping point, the odds seem equal. The climate is an infinitely complex chaotic system. We don’t know what switches the PDO from the cool phase to the warm phase and back again every thirty years or so. How do could we know what oceanic current change will have what effect overall on the globe?

I return again, however, to the question of relative size. Averaged over the globe, the earth receives almost 500 W/m2 (170 solar plus 320 IR). In the tropics, the day to night swing is about a kilowatt/m2 (1000 Watts/m2).

If CO2 were to double tomorrow, according to IPCC figures it would give us a forcing change of about 3.7 W/m2. That’s less than 1% change in downwelling radiation. It is a tiny, third order forcing. And in the tropics, because the solar input is so large, CO2 makes even less change in the total forcing. If the earth were to be tossed into a tipping point by less than 1% change in forcing, it would have fallen off its perch centuries ago.

I’ll tell you what I don’t like. Black soot. Falls on ice and melts it. Ever toss cold ashes from a dead fire out on the snow? Melts right down through the snow as the black carbon pick up solar heat, it just keeps going. The gift that keeps on giving. Plus carbon floats on water, so it stay up at the top absorbing sunlight. Talk about forcings, that’s a strong one. Lots of it gets swept up in the Northern Hemisphere and is deposited on snow and ice in the Arctic and sub-Arctic regions. That’s a forcing worth being concerned about.

But CO2? No, too small to worry about. It’ll get adjusted out by the thunderstorm and cumulus governor system. A 1% adjustment in overall albedo will cancel out a CO2 doubling. The Earth has been here before …

Next, I would take gentle exception to your claim that

The main driver of today’s global ocean circulation system is the Thermohaline system (TH), not solar irradiance

Oceanic circulation is driven at both ends of the heat engine. At the hot end, surface waters warm, expand, and flow by gravity towards the poles. At the same time polar waters radiate away their heat into the cold polar sky, cool, sink, and flow towards the equator to complete the circuit. As you imply, either a hot end or a cold end by itself is enough to drive this kind of thermo-circulation. In the case of the earth, however, we have both.

The change in current caused by fresh water being removed and replaced by the freezing and melting of the ice averages out over the year. It intensifies the current when it freezes as you explain. On the other hand, it slows the same current when it thaws. Overall, I’d expect there to be no significant net effect. Also, most of the year any particular part of the ocean is neither freezing nor thawing. So on any given square metre of ocean, the annual current change from freezing/thawing will be small.

Finally, the idea that evaporation density driven circulation (HT circulation) will take over as the dominant force seems extremely doubtful. It’s so small. Evaporation in the tropics is on the order of a cm/day. To dilute this effect by one hundred to one, it suffices to mix up the top metre of water. And that top meter is well mixed over most of the tropical ocean every day.

At night, of course, that slightly denser, slightly saltier water joins the radiation cooled surface water. It drops down one of the descending columns of water at night, and mixes with the main upper layer of the ocean. There’s a great temperature and salinity chart here. You can see that the salinity is not penetrating very deep into the Pacific.

You can also see that the cold water is rising at the equator, being heated, and spreading out towards both poles. At the equator, this rising cool water overwhelms the downward flow of the saline water, pushing that towards the poles as well. There, without the uprising water at the equator, it can sink deeper into the ocean and slowly mix away. There is a corresponding cross section of the Atlantic here, scroll down. It shows the same features of rising water at the equator and spreading warmth and salinity at the surface.

So no, I don’t see HT circulation dominating that any time soon …

Thanks for your ideas, they push me to think and explore.

w.

From Science News

Cold Water Ocean Circulation Doesn’t Work As Expected
ScienceDaily (May 14, 2009) — The familiar model of Atlantic ocean currents that shows a discrete “conveyor belt” of deep, cold water flowing southward from the Labrador Sea is probably all wet.

New research led by Duke University and the Woods Hole Oceanographic Institution relied on an armada of sophisticated floats to show that much of this water, originating in the sea between Newfoundland and Greenland, is diverted generally eastward by the time it flows as far south as Massachusetts. From there it disburses to the depths in complex ways that are difficult to follow.

A 50-year-old model of ocean currents had shown this southbound subsurface flow of cold water forming a continuous loop with the familiar northbound flow of warm water on the surface, called the Gulf Stream.

“Everybody always thought this deep flow operated like a conveyor belt, but what we are saying is that concept doesn’t hold anymore,” said Duke oceanographer Susan Lozier. “So it’s going to be more difficult to measure these climate change signals in the deep ocean.”

And since cold Labrador seawater is thought to influence and perhaps moderate human-caused climate change, this finding may affect the work of global warming forecasters.

Original study is subscription, abstract here

Given that our understanding of what the oceanic currents do now is incomplete, our understanding of currents in the past must necessarily be poorer than that of today. As the study shows, the ocean currents are not the simple lines we like to draw on charts. They are complex networks that shift location and speed and direction on scales from minutes to months to millennia.

So you are correct to identify the changes in the continents, particularly opening and closing gaps between islands and continents, as being crucial.

On a shorter timescale, things like the PDO indicate that there is more than one “quasi-stable” pattern in which the oceanic currents can flow.

Regarding the concern you expressed at the end:

But the big unknown is, what whould happen if humans manage to influence the climate enough to weaken to HT system. Climate systems appear to often switch abruptly, and we don’t know if the current climate system is robust enough to ignore what we’re doing to it.

The changes that humans have made to the surface of the earth are likely to have warmed it. Chop down the trees and you chop down the clouds. More sun plus less moisture means greatly enhanced surface heating (more heating plus less evaporative cooling).

I’d say that “are we pushing the climate away from a tipping point” is as valid as “are we pushing the climate towards a tipping point”. Since we have no knowledge or definition of what might constitute a tipping point, the odds seem equal. The climate is an infinitely complex chaotic system. We don’t know what switches the PDO from the cool phase to the warm phase and back again every thirty years or so. How do we know what change will have what effect overall?

I return again, however, to the question of relative size. Averaged over the globe, the earth receives almost 500 W/m2 (170 solar plus 320 IR). In the the day to night swing is about a kilowatt/m2 (1000 Watts/m2).

If CO2 was to double tomorrow, it would be 3.7 W/m2. That’s less than 1%. It is a tiny, third order forcing. And in the tropics, because the solar input is so large, CO2 makes even less change in the total forcing. If the earth were to be tossed into a tipping point by less than 1% change in forcing, it would have fallen off its perch centuries ago.

I’ll tell you what I don’t like. Black soot. Falls on ice and melts it. Ever toss cold ashes from a dead fire out on the snow? Melts right down through the snow as the black carbon pick up solar heat, it just keeps going. The gift that keeps on giving. Plus it floats on water, so it stay up at the top absorbing sunlight. Talk about forcings, that’s a strong one. Lots of it gets swept up in the Northern Hemisphere in the Arctic and sub-Arctic regions. That’s worth being concerned about.

But CO2? No, too small to worry about. It’ll get adjusted out by the thunderstorm and cumulus governor system. A 1% adjustment in overall albedo will cancel out a CO2 doubling. The Earth has been here before …

Thanks for your ideas, they push me to think and explore.

w.

From Science News

Cold Water Ocean Circulation Doesn’t Work As Expected
ScienceDaily (May 14, 2009) — The familiar model of Atlantic ocean currents that shows a discrete “conveyor belt” of deep, cold water flowing southward from the Labrador Sea is probably all wet.

New research led by Duke University and the Woods Hole Oceanographic Institution relied on an armada of sophisticated floats to show that much of this water, originating in the sea between Newfoundland and Greenland, is diverted generally eastward by the time it flows as far south as Massachusetts. From there it disburses to the depths in complex ways that are difficult to follow.

A 50-year-old model of ocean currents had shown this southbound subsurface flow of cold water forming a continuous loop with the familiar northbound flow of warm water on the surface, called the Gulf Stream.

“Everybody always thought this deep flow operated like a conveyor belt, but what we are saying is that concept doesn’t hold anymore,” said Duke oceanographer Susan Lozier. “So it’s going to be more difficult to measure these climate change signals in the deep ocean.”

And since cold Labrador seawater is thought to influence and perhaps moderate human-caused climate change, this finding may affect the work of global warming forecasters.

Original study is subscription, abstract here

Given that our understanding of what the oceanic currents do now is incomplete, our understanding of currents in the past must necessarily be poorer than that of today. As the study shows, the ocean currents are not the simple lines we like to draw on charts. They are complex networks that shift location and speed and direction on scales from minutes to months to millennia.

So you are correct to identify the changes in the continents, particularly opening and closing gaps between islands and continents, as being crucial.

On a shorter timescale, things like the PDO indicate that there is more than one “quasi-stable” pattern in which the oceanic currents can flow.

Regarding the concern you expressed at the end:

But the big unknown is, what whould happen if humans manage to influence the climate enough to weaken to HT system. Climate systems appear to often switch abruptly, and we don’t know if the current climate system is robust enough to ignore what we’re doing to it.

The changes that humans have made to the surface of the earth are likely to have warmed it. Chop down the trees and you chop down the clouds. More sun plus less moisture means greatly enhanced surface heating (more heating plus less evaporative cooling).

I’d say that “are we pushing the climate away from a tipping point” is as valid as “are we pushing the climate towards a tipping point”. Since we have no knowledge or definition of what might constitute a tipping point, the odds seem equal. The climate is an infinitely complex chaotic system. We don’t know what switches the PDO from the cool phase to the warm phase and back again every thirty years or so. How do we know what change will have what effect overall?

I return again, however, to the question of relative size. Averaged over the globe, the earth receives almost 500 W/m2 (170 solar plus 320 IR). In the the day to night swing is about a kilowatt/m2 (1000 Watts/m2).

If CO2 was to double tomorrow, it would be 3.7 W/m2. That’s less than 1%. It is a tiny, third order forcing. And in the tropics, because the solar input is so large, CO2 makes even less change in the total forcing. If the earth were to be tossed into a tipping point by less than 1% change in forcing, it would have fallen off its perch centuries ago.

I’ll tell you what I don’t like. Black soot. Falls on ice and melts it. Ever toss cold ashes from a dead fire out on the snow? Melts right down through the snow as the black carbon pick up solar heat, it just keeps going. The gift that keeps on giving. Plus it floats on water, so it stay up at the top absorbing sunlight. Talk about forcings, that’s a strong one. Lots of it gets swept up in the Northern Hemisphere in the Arctic and sub-Arctic regions. That’s worth being concerned about.

But CO2? No, too small to worry about. It’ll get adjusted out by the thunderstorm and cumulus governor system. A 1% adjustment in overall albedo will cancel out a CO2 doubling. The Earth has been here before …

Next, I would take gentle exception to your claim that

The main driver of today’s global ocean circulation system is the Thermohaline system (TH), not solar irradiance

Oceanic circulation is driven at both ends of the heat engine. At the hot end, surface waters warm, expand, and flow by gravity towards the poles. At the same time polar waters radiate away their heat into the cold polar sky, cool, sink, and flow towards the equator to complete the circuit. As you imply, either a hot end or a cold end by itself is enough to drive this kind of thermo-circulation. In the case of the earth, however, we have both.

The change in current caused by fresh water being removed and replaced by the freezing and melting of the ice averages out over the year. It intensifies the current when it freezes as you explain, but it slows the same current when it thaws. Overall, I’d expect there to be no significant net effect. Also, most of the year any particular part of the ocean is neither freezing nor thawing. So on any given square metre of ocean, the annual current change will be small.

Finally, the idea that evaporation density driven circulation (HT circulation) will take over as the dominant force seems extremely doubtful. It’s so small. Evaporation in the tropics is on the order of a cm/day. To dilute this effect by one hundred to one, it suffices to mix up the top metre of water. And that top meter is well mixed over most of the tropical ocean every day.

At night, of course, that slightly denser, slightly saltier water joins the radiation cooled surface water. It drops down one of the descending columns of water at night, and mixes with the main upper layer of the ocean. There’s a great temperature and salinity chart here. You can see that the salinity is not penetrating very deep into the Pacific.

You can also see that the cold water is rising at the equator, being heated, and spreading out towards both poles. At the equator, this rising cool water overwhelms the downward flow of the saline water, pushing that towards the poles as well. There, without the uprising water at the equator, it can sink deeper into the ocean and slowly mix away. There is a corresponding cross section of the Atlantic here, scroll down. It shows the same features of rising water at the equator and spreading warmth and salinity at the surface.

So no, I don’t see HT circulation dominating that any time soon …

Thanks for your ideas, they push me to think and explore.

w.

The main driver of today’s global ocean circulation system is the Thermohaline system (TH), not solar irradiance. Basically when sea ice forms at high latitudes it leaves behind near freezing and very saline waters that sink. In the North Atlantic this can generate a volume transport of 15 sverdrup (1 Sv = 1 million cubic meters per second, equivalent to all the water input of the worlds rivers), and reaches 150Sv by the time it joins the deep Circum-Antarctic current.

When no significant polar ice exists, then the dominant regime is Halothermal circulation (HT), which is driven by the evaporation at low latitudes that leaves behind heavy saline waters to sink. This is no mainly driven by solar irradiance, but it is calculated to be 1-2 orders of magnitude weaker than the Thermohaline system. Note that these HT waters are relatively warm and only sink due to their salinity, while TH deep waters are saline and cold; therefore we have much weaker circulation, plus it’s likely that these ‘deep’ waters don’t easily turn over the whole ocean, leading to stratification and stagnation (during the Eocene deep waters are thought to have reached 14 degrees C, compared to the near zero of today).

A lot of the major changes in global climate during the Cainozoic are probably due to continental rearrangement, when old ocean passages closed (Tethys, Panama, Indonesian Gateway almost) while others opened (Drake Passage, Tasman Strait, Denmark Strait and Iceland Faroe Passage), the global climate very abruptly stepped from Greenhouse to IceHouse mode.

So what the air temperatures are in our IceHouse world has been secondary to the ocean system in producing our current global climate. But the big unknown is, what whould happen if humans manage to influence the climate enough to weaken to HT system. Climate systems appear to often switch abruptly, and we don’t know if the current climate system is robust enough to ignore what we’re doing to it.

By saying ignorant stuff like “We really have very little knowledge of those far off times and lazy speculation is not helpful” you’re dismissing all the work of Palaeoclimatology, which includes Palaeontology, Sedimentology, Geochemistry, and a host of other disciplines.

Why does no one manage to hold in their heads the fact that the circulations in the air are seperate from the circulations in the oceans although influenced by them ?

If ocean circulations are weaker then less solar energy is taken away from the upper layers into deeper layers and ocean surfaces will warm.

Warmer ocean surfaces result in FASTER circulations in the air as the air tries to restore the balance between surfaces and space.

Furthermore those faster air circulations would result in faster circulation of solar energy through the upper layers of the oceans and serve to reduce any oceanic ’stagnation’.

We really have very little knowledge of those far off times and lazy speculation is not helpful, especially if it is designed to serve an agenda.

Moving away from the far off times to the present, the ocean and how it circulates the heat from the downwelling solar and infrared radiation is a fascinating and imperfectly understood subject.

Radiation heats and cools the ocean very unevenly, both temporally and spatially. First, spatially.

Spatially, the tropics receive most of the heat. When water heats it expands. It rises, and spreads out towards the poles. This is the driving force of the overall ocean circulation of the tropical heat to the poles. It is the oceanic counterpart of the atmosphere being heated and rising in the tropics.

The speed of this current varies with the amount of energy driving it (which in turn is regulated by clouds and thunderstorms). Note that the amount of energy transferred is a different thing than the temperature.

Again spatially, light penetrates tens of meters into the ocean. Infrared (greenhouse radiation), on the other hand, is absorbed in the first millimeter. This leads to very different outcomes. And this leads to the second uneven distribution, the temporal distribution of radiation.

During the day, the atmosphere is unstable because it is warmest at the bottom. Hot air rises, and it overturns. At night, the bottom of the atmosphere cools, and overturning stops. The atmosphere is thermally stable at night.

The opposite is true of the ocean. During the day, about 80% of the sunlight is absorbed in the upper ten meters of the ocean, and IR is absorbed right at the surface. At the very surface skin, IR immediately and strongly affects re-radiation and evaporation rates. Sunlight affects those as well, but half of the solar energy is absorbed at depths deeper than half a meter. A quarter of the solar energy is absorbed below five meters. Sunlight heats the bulk of the top of the ocean. It has less immediate effect on outgoing radiation or evaporation.

Now, other things being equal, heat in the ocean doesn’t mix downwards. It rises. So during the day, the ocean is generally thermally stratified and stable, with the warmest water at the top. The top skin gets all the IR plus some of the solar energy, so it is strongly radiating and evaporating. Below it the solar energy is absorbed logarithmically, with deeper layers receiving less energy. This increases the thermal stratification.

At night, on the other hand, the only downwelling radiation is the IR absorbed in the top mm. The body of the ocean is no longer warming. Outgoing IR radiation is greater than incoming (because the earth is warmer than the atmosphere, and thus radiates more). The skin starts to cool. As soon as it becomes cooler than the underlying layer, it will start to sink through that warmer water until it reaches water of its own temperature. This happens in well defined descending columns of cooler water. These are fed by a larger drainage area around the top of each column.

In between the descending columns, the water is slowly rising to the surface. Curiously, this is the mirror image of what happens in the atmosphere during the day. There, the bulk air slowly moves toward the surface in between the columnar thunderstorms with their rapidly rising warm air. In the ocean, the bulk ocean slowly moves toward the surface in between the rapidly sinking columns of cool water.

The system naturally produces the maximum possible radiative cooling and evaporation. Radiative cooling and evaporation are dependent on the temperature of the free surface of the water. What’s happening a centimeter below the surface doesn’t change either of those in the slightest. It’s the skin temperature that counts. And other things being equal, the hottest water in the whole column is always at that top surface.

This leads to a curious situation where the instantaneous energy flow through the ocean surface is not dependent on the bulk temperature of the ocean. It depends only on the skin temperature, which is to say, it is generally the temperature of the warmest water.

Makes for complex calculations, and prevents easy or simple answers …

w.

Regarding the change in solar strength (S): Most palaeotemperature graphs are only for the past 600 million years or less (the Phanerozoic). S is thought to increase by 10% every billion years, so since the Ediacaran it has increased 6%, leading to a shortfall of 0.06 * 340 W/m2 = 20.4 W/m2 back then. For CO2 alone to make up for this, it would have required 20.4/3.7 = 5.5 doublings = ca 10,000ppmv CO2. CO2 is thought to have been about 7000ppmv at the start of the Phanerozoic, pretty close from where I stand.

That is true. And CO2 is also though to have been much lower at other geological times.

But as I said above, it is improbable that we would have had changing forces (increasing solar and decreasing GHG) that would have so nearly and neatly balanced each other for 600 million years. In part, the problem is that one is linear (solar forcing change). The other is logarithmic (CO2 forcing change). What would keep them in balance? It’s one of those “possible but doubtful” things.

One of the citations upstream showed that tropical cumulus don’t form when the sea surface is below 299 K. When the sea is below that temperature, it gets the full force of the sun. In the tropics at noon, this is over a kilowatt per square meter. Our climate system has a lot of power in reserve to warm up the earth when it gets cold. That’s what’s keeping it in balance day in and day out, and thus century in and century out … not changing CO2.

w.

Why does no one manage to hold in their heads the fact that the circulations in the air are seperate from the circulations in the oceans although influenced by them ?

If ocean circulations are weaker then less solar energy is taken away from the upper layers into deeper layers and ocean surfaces will warm.

Warmer ocean surfaces result in FASTER circulations in the air as the air tries to restore the balance between surfaces and space.

Furthermore those faster air circulations would result in faster circulation of solar energy through the upper layers of the oceans and serve to reduce any oceanic ‘stagnation’.

We really have very little knowledge of those far off times and lazy speculation is not helpful, especially if it is designed to serve an agenda.

Variability of UVB and global cloud cover
S.H. Larsen G.E. Bodeker E. Pallé 2007
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Abstract. The role of Dimethyl Sulphide (DMS) in regulating climate has been the focus of much research in the last 20 years. In particular, that warmer ocean temperatures might increase the production of DMSP and subsequent flux of DMS to the atmosphere, increasing the number of cloud condensation nuclei and so cloud albedo and duration. In turn this could act to reduce solar heating of the surface, and such a negative feedback would act as a natural thermostat.

However, temperature is not the only environmental variable that may affect the production of DMS. Another forcing factor is the flux of ultraviolet (UV) light into the
oceans, Larsen (2005). It is hypothesised that increased UV decreases the flux of DMS to the atmosphere. In which case, cloud cover is reduced, further enhancing the flux of UV into the ocean, and vice versa. In this case a positive feedback would result. The oceans most likely to be susceptible to such a forcing are those where the mixing depth is lowest, and incoming solar-UV flux greatest. These include the subtropics (and higher latitude oceans in summer). The effect of variations in the solar flux on any DMS-climate link are therefore more complex – enhanced solar heating potentially having a negative feedback, but the simultaneously enhanced solar-UV flux having a positive feedback.

In order to test this hypothesis, UVB data were compared with Earthshine data (a measure of the Earth’s albedo) over the Pacific and Atlantic oceans. Significant negative correlations were obtained, especially in the northern hemisphere Pacific and Atlantic in the summer half of the year