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More specifically, I've seen some discussion of this article:

http://www.realclimate.org/index.php/archives/2006/09/why-greenhouse-gases-heat-the-ocean/

which claims that the observed ocean warming is explained by the ocean skin absorbing long-wavelength radiation. What I am asking is: is this mechanism necessary for ocean warming to occur? My naive understanding was that our increasing the magnitude of the greenhouse effect meant that there was less radiation escapting to space, and therefore the average temperature of the entire ocean+earth+atmosphere system will increase until it reaches a new equilibrium, where outgoing radiation again equals incoming. Is this correct? And if it is, does it not imply that the ocean must also get warmer, simply because it is a thermally coupled part of the entire warming system? I had someone tell me that the a warming atmosphere could not warm the ocean beyond an infinitesimal amount, because the atmosphere has a much lower heat capacity. But it seems to me that the constraint on the final equibilibrium temperature means that all components must warm, no matter how inefficient the means of energy transfer between them - as long as there is some means for energy transfer, increasing the overall temperature must increase each of the components. Am I right, or have I misunderstood?

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  • $\begingroup$ i think the answer to this is water absorb heat from the sun better than it reflects it. $\endgroup$ – trond hansen Apr 17 '17 at 12:18
  • $\begingroup$ Let's ask a more extreme question: if the ocean did not absorb any radiation from the sun whatsoever, would it warm by a significant amount purely because it is thermally coupled to the entire system, when that entire system has to warm to a certain temperature due to radiation imbalance? $\endgroup$ – Paul Miller Apr 17 '17 at 12:21
  • $\begingroup$ @PaulMiller - well you can look at the past and then forecast the future - nature.com/articles/ncomms8423 $\endgroup$ – gansub Apr 18 '17 at 9:59
  • $\begingroup$ @gansub - thanks, that looks very interesting. Really I'm talking about a very simplified model of the earth, because I'm trying to understand the fundamentals of the thermodynamics. See my comment to Trond. I've had someone claim that LW absorption was the only way that AGW could ever warm the ocean by a significant amount, and that LW absorption had no real evidence to support it. My response was that the ocean is guaranteed to warm eventually just by heat transfer from the atmosphere, even if it's slow. Am I right? Would the ocean eventually warm, and by a significant amount? $\endgroup$ – Paul Miller Apr 18 '17 at 11:09
  • $\begingroup$ @PaulMiller- greater frequency of El Ninos is probably attributed to oceans warming more significantly than land. $\endgroup$ – gansub Apr 18 '17 at 12:21
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My naive understanding was that our increasing the magnitude of the greenhouse effect meant that there was less radiation escapting to space

That's 100% correct. If we assume constant solar input, there's only two ways the Earth's surface temperature can change. Albedo and Thermal radiation. Greenhouse gas driven climate change means exactly what you said - less heat radiates off Earth into space. Most of this heat goes into the Ocean.

And if it is, does it not imply that the ocean must also get warmer, simply because it is a thermally coupled part of the entire warming system? I had someone tell me that the a warming atmosphere could not warm the ocean beyond an infinitesimal amount, because the atmosphere has a much lower heat capacity.

Your friend is half right, and half wrong. Air has a bit over 1/4th the heat capacity compared to water and it's about 800 times less dense, so he's correct, but it's not that simple.

Sunlight - somewhat counter-intuitively, isn't great at warming oceans because the photons from sunlight are energetic enough to evaporate water molecules into gas molecules. Oceans have low albedo which means they absorb most of the energy from the sunlight, but much of that heat is lost in evaporation by visible light photons. While that has nothing to do with your question, it's worth pointing out that sunlight isn't as good at warming oceans as one might think. (If anyone has one of those solar mirror ovens, I'd be curious to see how well they work on pure water . . . just out of curiosity, evaporation loss vs rate of warming).

The back-radiation from the atmosphere is comparatively much less total solar energy, but oceans are good at absorbing and storing thermal back-radiation reflected back off the greenhouse gas rich atmosphere into the ocean. This is a tiny amount of the total heat Earth gets from sunlight, and the increase of this radiation due to greenhouse gas is a fraction of one percent of solar energy, but it adds up.

One way to explain this is that 85 degree air will warm 80 degree water. That's a thermodynamic law. It just takes a while and because the heat capacity and density of water is much greater, it takes about 4 liters of air to give 1 degree back to warm 1 cc of water 1 degree. But despite the inefficiency, warmer air still transfers heat into colder water. It takes many decades, perhaps centuries, for the oceans to catch up to the warming air, but air, however inefficiently, does warm the oceans.

The quirk in this, is that the oceans, despite warming much more slowly than the air, are still absorbing over 90% of the trapped heat added by the increase in greenhouse gas. It's a matter of scale. Oceans warm slowly because they're enormous and always circulating and it takes much more energy to war them, but they also absorb most of the heat, for the same reason, they're very good at holding heat. Slow to heat up, but also, slow to cool down. That's why bodies of water often feel warm when you go swimming at night.

I should probably add something about increased evaporation in higher air temperature, which effectively cools the oceans and surface air, but also increases the greenhouse effect with an increase in water vapor, but running those numbers is a bit over my pay-grade. The greater efect is the one mentioned above.

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  • $\begingroup$ There are many misconceptions in this answer, above. $\endgroup$ – Knob Scratcher Apr 19 '17 at 5:01
  • $\begingroup$ @KnobScratcher Such as? $\endgroup$ – userLTK Apr 19 '17 at 5:27
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    $\begingroup$ Thanks for the great answer. Did you really mean 'That's in a nutshell, simple conduction air to water' though, because it sounded as though that paragraph was purely talking about a radiative effect? I find the heat capacity issue confusing, because the overall radiative imbalance caused by increased greenhouse effect means that the entire system is being driven to a new, higher average temp. So every time the warmer atmosphere loses heat to the ocean, its temp. drops and the overall radiative imbalance increases. So I don't know how to calculate the speed of transfer to the ocean. $\endgroup$ – Paul Miller Apr 19 '17 at 11:43
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    $\begingroup$ @trondhansen I read it as being the specific heat capacity, i.e., about 1 J/g/K for dry air and 4 J/g/K for water. $\endgroup$ – Deditos Apr 19 '17 at 11:46
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    $\begingroup$ @PaulMiller measuring the entire oceans change in temperature is a pretty big task. There's some variation with El Nino and La Nina too, El Nino puts more heat into the air, La Nina draws more heat from the Air. I think the simplest way to look at it is the laws of thermodynamics. Air that's 84 degrees over ocean that's 82 degrees, Air can only cool to about the ocean temperature, never below it. Warming the air very slowly warms the ocean. Prior to GHG, there was an air-ocean equilibrium of sorts. Warm the air with GHG, the ocean very slowly follows. The equilibrium creeps up. $\endgroup$ – userLTK Apr 19 '17 at 18:35
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That's in a nutshell, simple conduction air to water.

No....it's not so simple.....far from it. In fact, there are several rather complicated processes occurring simultaneously, none of which involve the simple transfer of heat from warm air to cool sea water, as stated by userLTK, above. From Skeptical Science:
How Increasing Carbon Dioxide Heats The Ocean

Sunlight penetrating the surface of the oceans is responsible for warming of the surface layers. Once heated, the ocean surface becomes warmer than the atmosphere above, and because of this heat flows from the warm ocean to the cool atmosphere above.

But really, you should read the entire text for a good explanation of the process that leads to warming seas. Another important resource is found at the Scripps Institution of Oceanography:

Physics of greenhouse effect and convection in warm oceans

On average, convective regions are more humid, trap significantly more longwave radiation, and emit more radiation to the sea surface. The greenhouse effect in regions of convection operates as per classical ideas, that is, as the SST increases, the atmosphere traps the excess longwave energy emitted by the surface and reradiates it locally back to the ocean surface. The important departure from the classical picture is that the net (up minus down) fluxes at the surface and at the top-of-the atmosphere decrease with an increase in SST; that is, the surface and the surface-troposphere column lose the ability to radiate the excess energy to space.

The cause of this super greenhouse effect at the surface is the rapid increase in the lower-troposphere humidity with SST; that of the column is due to a combination of increase in humidity in the entire column and increase in the lapse rate within the lower troposphere. The increase in the vertical distribution of humidity far exceeds that which can be attributed to the temperature dependence of saturation vapor pressure; that is, the tropospheric relative humidity is larger in convective regions.

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First we need to see if your question is based on facts. If the only energy in the climate system comes from the sun, what things can increase the energy in the system, other than the sun? The answer is: nothing. To increase temperature you need to increase the intensity of emitted heat where the temperature increase. Since the only source of energy is the sun, how could we increase the intensity anywhere, if not the intensity of solar irradiation is increased? This is a surprising mistake done by the entire climate science. The claim is that increasing the amount of a potent heat absorber would increase the intensity of emitted heat from the surface. If you add a heat absorber that absorbs heat from a body, it cannot cause warming. Often it is claimed to retain, or delay heat loss. But that cannot be true according to thermal physics. Preventing heat loss is exactly what we do by insulating the boundary of the system we want to stay warm. Thermal insulation is a logic simple thing, you can read about it here:

https://en.wikipedia.org/wiki/Thermal_insulation

"Thermal insulation provides a region of insulation in which thermal conduction is reduced or thermal radiation is reflected rather than absorbed by the lower-temperature body."

As you can see, it is without doubt very clearly stated, that preventing heat loss, or retaining heat, is done in the exact opposite way to what the theory of global warming claims. Absorption is what you want to avoid to prevent heat loss. There is a lot of things in the warming science-camp that indicate a lack of physics education in their field of science. Actually, every single argument in the greenhouse theory is a head-on violation of known, proven 100% consensus physics.

So, first of all, according to proven physics, it is highly unlikely that there is a warming climate at all. Secondly, the ocean cannot warm, if the amount of heat from the sun doesn´t increase. And we know that it doesn´t.

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  • $\begingroup$ your statement about the temparature not increasing is like herding kittens it takes a lot of work and the succses rate is quite low. $\endgroup$ – trond hansen May 6 '17 at 5:32
  • $\begingroup$ Your answer is flat out not correct. Heat comes from the sun, but we know that hundreds of millions of years ago the sun was less luminous and radiated less heat but the Earth was warmer. The sun also doesn't drive the rise and fall of ice ages, the orbit and tilt of the Earth does, at least, mostly (solar cycles might play a supporting role). But, bottom line, it's not just the sun, it's how much long-wave radiation is trapped and it's how much visible light is reflected. You're also wrong on consensus Physics. $\endgroup$ – userLTK May 6 '17 at 6:52
  • $\begingroup$ If only it was possible to "trap" longwave radiation with cold air, you would have an argument. Didn´t you read the wiki-link? It would have informed you how heat is "trapped". The exact mechanism that the greenhouse theory claim as a "trapping" mechanism, is what you need to avoid to "trap" heat in reality. Absorption in a colder body, which is what co2 does, is exactly what you prevent with thermal insulation to prevent heat loss. Consensus physics. The greenhouse theory is consensus greenhouse theory, and every single part of it violates known, proven and successfully applied physics. $\endgroup$ – Emil Junvik May 6 '17 at 15:50
  • $\begingroup$ If you want somewhere to propose your crank theory that the greenhouse effect doesn't exist, you have the whole internet for that. SO is not the place. $\endgroup$ – Paul Miller May 6 '17 at 19:07

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