Rhoda

'Nothing much is happening and if anything does, we should (and can) adapt to it'.
if by 'we' you mean the human race then I agree with you but if you mean our civilisation/society then I am not so sure.
Whatever the 'warmista' say I would predict that the world will continue through the same cycles that it has followed for over 4 billion years. CO2 can not do much about the Milankovitch cycles or the movement of our solar system and galaxy.
Geological records show that the earth has oscillated between hothouse and icebox and most of its history has been hothouse (10 deg C higher than today). This information comes from websites that predate the climate change debate, it includes fossils of crocodiles and palm trees found in the UK. From memory the earth spent 90% of its time in hothouse conditions and 10% in ice age, our current interglacial climate accounts for 10% of the time spent in ice age.
On the face of it we have chosen to create our civilisation in the rarest climate the earth ever experiences!
Nobody knows whether the end of this interglacial will bring a return to the current ice age or a change to hothouse, if we return to ice age then I do not think our technology will be able to protect the general population.

I suppose I ought to qualify that. There is no level of historic heat we can't adapt to, even if our ancestors may have had to migrate out of Africa during past climate events. Cold is another thing. We can survive it, some of us. I can't begin to say how we would look after 100.000 years. In any scenario, on second thought.

Dung:

As the Aussies say, "No worries, mate." All is good. :-)

Jack:

One of the very powerful concepts you learn immediately in an introductory thermodynamics course is that of a "control volume." For whatever control volume you define, as long as you properly keep track of all transfers across the boundaries, you don't have to concern yourself with what happens inside when performing energy balance calculations.

So defining the earth and its atmosphere together as a control volume, the only transfers (that aren't absolutely trivial) across the boundary with space are radiative energy transfers. No conductive or convective transfers, no mass transfers. To the extent that we can measure these radiative transfers -- shortwave from the sun, longwave to space -- we can figure the energy balance of the earth/atmosphere system. It appears to me that we know these transfers to within +/- 5 W/m2, which is good enough to know that there is an effect, but not good enough to know subtle changes in that effect.

It's a lot like your own financial accounting. What matters are the inputs to your accounts and outputs from them. Transfers between your own accounts do not change your wealth.

"But let’s not forget that the entire planet is literally powered by the sun. Incoming solar energy drives the Earth’s weather systems, winds and ocean currents. [...] This uses a lot of solar power, so it’s hardly surprising that there’s a mismatch between incoming and outgoing energy."

In the sense you mean, it doesn't use any power. Energy is conserved. All the energy that drives the convection cycles is turned into heat by friction and turbulence. All the energy converted to useful work by a heat engine goes the same way. What 'makes things go' is the way the heat/energy is distributed - the differences in temperature - not the energy itself. That's a subtly different concept called 'entropy'. It's the entropy that gets 'used up' by heat engines and weather; the energy just moves around without increasing or decreasing.

Whether there is a mismatch depends on whether you're talking about the sea/ground surface, or the Earth as a whole. The ground only gets enough incoming sunlight to warm it to about -20 C. At this temperature, it would be radiating exactly as much as it was getting and would be in equilibrium. Since the surface is a lot warmer than that, it's radiating more energy than the sunlight provides directly, and unless it was getting some more from somewhere else, would cool to - 20 C. If the atmosphere was transparent, then all this energy would escape the planet, and the planet as a whole would be losing energy, and hence cooling. That doesn't happen, because the radiation from the surface does not escape directly to outer space, because the atmosphere is partly opaque.

The same thing happens whenever you cover the ground with something opaque. The sunlight is blocked from the inside of your house, so like the ground, the walls and floor of your house are receiving far less energy from direct sunlight than it is emitting, far less than even the ground outside. The roof of your house would only cool to -20 C but the inside of your house ought to be like an Antarctic winter!

The reason your house doesn't freeze when you block the sun out is that although all the internal walls are radiating, that radiation only crosses the room and gets absorbed by the opposite wall. If both walls are at the same temperature, the same amount of radiation is emitted both ways, and both walls absorb exactly as much as they emit, giving no net change. You can't just count the radiation from the sun - you also have to include the radiation from everything else, or of course things won't balance. Sometimes, if everything is at the same temperature you can cancel the radiation emitted against the radiation received and ignore it. The radiation emitted by the material inside a solid body is like this. Because any radiation emitted is balanced by an equal amount of radiation coming back, you can ignore it, and assume that bodies only emit radiation from their outer surfaces. But that's not how things actually work, and if you're going to question fundamentals like this then you need to understand how it really works.

So, the ground is in energy balance because it not only gets energy from the sun, but also emitted back from the sky like the floor of your house absorbs energy from the ceiling, as well as being transported horizontally by convection. And the Earth as a whole is in energy balance because the 'visible' surface of the planet that emits thermally to space is high up in the atmosphere and a lot colder (about -20 C on average), and so emits to outer space only as much as the Earth absorbs. Most of the outgoing radiation from the hot surface has to be blocked - outer space only sees the cold top to the atmosphere radiating.

The reason that Venus, Earth, and Mars have very different surface temperatures is that the distance between that cold top radiating to space and the surface is very different. Venus has thick opaque clouds 80 km above the surface. Earth has water vapour and other trace gases in the troposphere ranging 0-10 km and averaging about 5 km up. Mars has a very thin, pure CO2 atmosphere that emits to space from less than 1 km up. It's not the amount of GHGs that matters, but the altitude of the opaque cover. More GHGs raises the altitude, which warms the surface up. Unless you're proposing that you can somehow add GHGs without the average altitude of emission to space increasing (or somehow reduce the lapse rate, or reduce the incoming sunlight to compensate), some degree of warming is inevitable.

The scientific argument is about the feedbacks, not the greenhouse effect itself.

"however I would be more impressed if you explained why the planet is not warming and how CO2 is involved if that is OK?"

Obviously, the planet is not warming because CO2 is not the only thing affecting the temperature.

It's a bit like the weather. Everybody tells me that summer is warmer than winter because the sun is higher in the sky. At this time of year, the sun is climbing, so it ought to be getting warmer. But today was colder than it was two days ago!

Has the cycle of the seasons stopped? Do you think it would be reasonable for anyone to make that claim on the basis of three days weather? Of course you wouldn't. So why would you expect me to have any problem with 'the pause'?

The greenhouse warming predicted from CO2 alone, without feedbacks is about 1 C/doubling, and since we've had about half a doubling we ought to expect about 0.5 C of warming, multiplied by an unknown feedback factor. On top of that we get a lot of noise and variation from weather, clouds, ocean cycles, shifting convection patterns and ocean currents and so on, the magnitude of which is apparently somewhat larger, but the true distribution of which is not known.

Trying to separate a climate trend multiplied by an unknown and likely time-varying factor from a noisy, random, unknown and likely time-varying 'weather' distribution is not mathematically possible. All we can say for sure is that over time intervals 20 years and shorter the weather noise must be of at least comparable magnitude to the climate 'signal'. That doesn't tell us anything about how they compare on 50 or 100 year timescales. That doesn't tell us what the feedback factor is, or how much of the change seen is weather, or what precisely is causing what - if it even makes logical sense to separate individual independent causes in a non-linear system.

That it is colder here today than two days ago tells us that more is going on in the weather than the approach of spring. Likewise, if it warms up over the next few days, that doesn't mean that the warmth was caused by the changing season. It's perfectly reasonable to say so, and to criticise a forecaster who bases his forecasts solely on the calendar. But if you go too far and start claiming things that are not so, you risk the credibility of your own criticisms. The bad forecaster can get away with it, because he only has to be more accurate than you. That's why people like Watts, McIntyre, and the Bishop are not keen on these arguments.

However, that's not the reason they get banned on the main pages. The reason they're banned is that certain people would otherwise turn *every* thread into a radiative physics bunfight. You want to talk about new green legislation? Let's talk radiative physics! You want to talk about a new book or talk? Let's talk radiative physics! You want to discuss sea level rise, or glaciers, or ocean chemistry, or the education system, or electricity generation? Let's talk radiative physics! It gets tiresome. So it got banned, unless the Bishop chooses to put up a post *about* radiative physics. It's not about whether he's got strong enough empirical evidence for the position to override all alternatives (I'm pretty sure the Bishop wouldn't do that, on principle, even if he thought he had), it's about politeness and allowing other people to hold a conversation on other topics.

No offence was intended, I'm sure.

NiV, do you have an opinion on the feedback factor? Over or under unity? Seems to me that high positive feedbacks can be pretty much ruled out. And that NO feedback is linked solely to CO2 effects, temperature feedback can result from any temp change.

Somethings that slightly worry me. First, if CO2 and other ghgs are 'well-distributed' why isn't there more of them above the 50% of atm level as well as below? Would they not be more capable of radiating to space?

Next, tell me how lapse rate warms the surface? A lump of surface needs to be warmed by convection ,conduction or radiation. No doubt that's what happens. But how is the lapse rate involved?

Lastly, and this is a mere observation, isn't the radiation of the average, which is what you use, different from the average of the radiation, which is reality?

Nullius in Verba

The reason that Venus, Earth, and Mars have very different surface temperatures is that the distance between that cold top radiating to space and the surface is very different. Venus has thick opaque clouds 80 km above the surface. Earth has water vapour and other trace gases in the troposphere ranging 0-10 km and averaging about 5 km up. Mars has a very thin, pure CO2 atmosphere that emits to space from less than 1 km up. It's not the amount of GHGs that matters, but the altitude of the opaque cover. More GHGs raises the altitude, which warms the surface up. Unless you're proposing that you can somehow add GHGs without the average altitude of emission to space increasing (or somehow reduce the lapse rate, or reduce the incoming sunlight to compensate), some degree of warming is inevitable.

Thank you for that, having asked the question on several (many) occasions yours is the first explanation in layman's terms anyone has ever bothered to post. You have touched on several things which I believe are just as, if not more, important than CO2. As a result I'll continue to be a sceptic on CO2 being anything more than a negligible player.

It's my personal view that the "energy balance" calculations are a guess and not even an educated one as we've no real idea how much of the incoming E-M energy is converted into mass in the same way that we've no idea how much erosion is taking place (an energy sink), as Sir Patrick Moore was fond of saying "We just don't know".

Mike Jackson
Had the USS Enterprise (always CV-6 for me) been a bit more restrained in his comments and forthcoming with references he could have contributed much here and elsewhere.

Curt,

Sorry for my absence from the discussion for a while – I’ve had other demands on my time.

My previous comment was addressing the notion that the gap between measured incoming and outgoing energy needs to be explained. But so long as we have dynamic atmospheric and oceanic systems an imbalance is to be expected, and we seem to agree.

Inside a system, it matters not whether energy transfer is expressed as “heat” or “work”, as one is equivalent to the other. The point I was trying to make was that, since some incoming solar energy is doing work on Earth, e.g. driving ocean currents, weather systems, etc, the amount of energy available to be transferred back to space in the form of “heat” is reduced, so there will always be a discrepancy between incoming and outgoing energy. Whether this imbalance is increasing or not is a moot point.

Not that any of this is new – it has always been so.

To quote your final analogy about bank accounts, “Transfers between your own accounts do not change your wealth.” My response is that the application of bank charges most certainly does!

"NiV, do you have an opinion on the feedback factor? Over or under unity?"

Officially, my opinion is still "I don't know". It's one of those topics where the "unknown unknowns" are very likely to outweigh the known ones, let alone what's known about the subject.

However, unofficially I'd say that the Nic Lewis-style empirical evidence for a factor slightly over unity is at least plausible, and the best we've currently got. So I'd go with that until something better comes along, although I'm not strongly attached to it.

"Somethings that slightly worry me. First, if CO2 and other ghgs are 'well-distributed' why isn't there more of them above the 50% of atm level as well as below? Would they not be more capable of radiating to space?"

The main GHG is water vapour, which is *not* uniformly distributed.

The distribution of gases is not uniform because of the variation of atmospheric pressure with altitude. The air is denser at low altitudes, and hence so are all the gases that make it up.

I'm not sure what you mean by the "50% of atm level" but if you mean the level with 50% of the gas above/below it, then the reason there's not more of them above than below is that it is the 50% level. This is true by definition!

However, and as you note in your last query too, the "average" isn't a straightforward 'middle-of-the-atmosphere' average. It is instead a way of hiding behind an innocuous-sounding word a huge and hairy quantum-mechanical calculation involving databases of tens of thousands of absorption lines, and the computerised numerical solution of the rather complicated (by layman's standards) radiative transfer equations.

Some radiation does come from the ground and escapes directly to space. Some bounces off clouds. Some bounces off clouds and hits other clouds at a different altitude and temperature. It's all very messy - although at the same time is one of the empirically better-determined parts of the process. The MODTRAN and HITRAN software was developed by the military to model what their electro-optic sensors could see, (e.g. such questions as 'will you be able to see that anti-ship missile currently headed for you in time to shoot it down?', which they regard as a "kinda important thing to know", what with there being a thirteen billion dollar warship with 80-odd $100m advanced jet fighters embarked on it at stake on the receiving end) and they've done extensive testing to validate them. The people auditing them tend to be quite serious about it.

I'd not necessarily trust them on clouds, but they're pretty good at the near-surface clear air stuff.

For a slightly more basic and more accessible explanation (but not very!), see Manabe and Strickler 1964 figures 8b and 8c which show the differing contributions of the different gases by altitude. Incidentally, the explanation in section 2 of why the standard 'backradiation' calculation gives the wrong answer and why the lapse-rate approach is better is quite good, although it could be better. There's a much better one in Soden and Held 2000.)

"Next, tell me how lapse rate warms the surface? A lump of surface needs to be warmed by convection ,conduction or radiation. No doubt that's what happens. But how is the lapse rate involved?"

It would be slightly more accurate to say that the lapse rate is the vertical temperature gradient at which convection switches off and therefore stops cooling the surface.

The sun warms the surface, but the heat escapes very quickly by convection so the build-up of heat near the surface is limited. In an incompressible atmosphere, it would *all* escape, and you'd get no surface warming. But because air is compressible, and because gases warm up when they're compressed and cool down when allowed to expand, air circulating vertically by convection will warm and cool at a certain rate due to the changing atmospheric pressure. Air cools as it rises and expands, and warms as it descends and is compressed. This warming/cooling effect means that hot air no longer rises when it would cool faster from expansion than the surrounding air. Cold air can sit on top of warm air and be stable. The adiabatic lapse rate is why the tops of mountains are colder than their bottoms.

It's a bit like the way a pot of boiling water sticks at a temperature of 100 C. If you turn the gas up, the water boils more vigorously, carrying more energy off as steam, which balances the extra energy supplied and keeps the temperature still at exactly 100 C. The rate at which heat escapes is very non-linear - extremely fast for temperatures above the threshold, extremely slow for temperatures below it. So long as the system is driven hard enough, it will get driven up against the non-linear limit and held there. The lapse rate does the same thing, except that instead of fixing the temperature, it fixes its gradient so you get a rigid slope that can freely float up and down in level.

The temperature at the average altitude of emission to space converges on the temperature that radiates the same energy the Earth absorbs. All levels above and below it are held in a fixed relationship to it by the lapse rate. The temperature at any other level is the temperature at the emission altitude plus the lapse rate times the difference in heights. Hence, the temperature at the surface differs by the lapse rate times the average height of emissions to space.

It's interesting to consider what would happen if you had a strongly absorbing greenhouse material but a zero lapse rate. You'd get lots of backradiation, but no greenhouse warming. By marvelous happenstance we do have such a physical situation in the oceans. Water absorbs all thermal radiation within about 20 microns, making it something like 20,000 times more powerful a greenhouse material than the atmosphere. It's a (relatively) easy calculation to show that if radiation was the only way heat could be transported, as the backradiation argument assumes, the temperature a metre down would be several thousand degrees! But water is almost incompressible, having a lapse rate of around 0.1 C/km, and so convection nullifies it entirely. Fortunate, eh?

"Lastly, and this is a mere observation, isn't the radiation of the average, which is what you use, different from the average of the radiation, which is reality?"

Agreed! See above.

"@NiV thanks for that reminder that radiative physics talk has to controlled on threads that are not about it.
Someone should have said that at the beginning.. I knew but I forgot."

It's a point that most sceptic blog hosts feel very awkward about. On the one hand, sceptics are all for free speech, free debate, and being open to any challenge. It's the scientific method, and one of our biggest criticisms of the other side. On the other hand, some people are just obsessive about it. And it can put scientists off taking sceptics seriously. I became a sceptic after reading Steve McIntyre, and thinking "Hey, he's got a valid point!" I'd have likely had an entirely different attitude to sceptics if I'd run into the skydragons first. One of the things I like about climate sceptics is that they didn't let such political considerations lead them into shutting the debate down - they gritted their teeth and tolerated it for a long time. But eventually it got so difficult that most of them gave in.

It's a pity, because I think it's definitely worth discussing. There's some interesting physics, and it helps a lot of people to have a clearer understanding of what it's actually about. If people are open-minded, and I think most sceptics are, we can show the opposition how it's supposed to be done by fixing our own errors and misunderstandings through a scientific process of constructive challenge and debate. We can improve our game and get more sceptics in the public eye who are bullet-proof on the science. I think the other side are vulnerable in having a lot of pundits who don't properly understand the science themselves, and there are these horrible misconceptions floating around like 'backradiation' and the 'CO2 in a bottle' experiment, that we could definitely beat them on. But we have to understand it ourselves.

"That other variables can blur the effect of oncoming Spring, but not completely counter it.
Are you saying that the case of CO2 is similar at current levels ie that CO2 caused (rising) warming is being blurred by other factors, but it is still there?"

Yes. Although it's not clear, given the errors and uncertainties in measurement, and lack of knowledge of the noise distribution, whether it is detectable.

"Thank you for that, having asked the question on several (many) occasions yours is the first explanation in layman's terms anyone has ever bothered to post."

You may have missed them, but there are quite a few of them around. I've given the explanation here, at Judith Curry's, Watts up, Air Vent, Science of Doom, Roy Spencer's, and a few outsiders like Keith Kloor's. There's another guy, Leonard Weinstein, who was making the same arguments early on who is worth looking out for, too. I think he did some very good guest posts at ScienceOfDoom. Unfortunately, they tended to get buried in the massive pile-ons that usually happened whenever radiative physics got brought up, so they might be easy to miss.

One of the more famous ones is here:
http://judithcurry.com/2010/11/30/physics-of-the-atmospheric-greenhouse-effect/#comment-16901
The next-post-but-one 'Best of the Greenhouse' carries on the discussion.

"You have touched on several things which I believe are just as, if not more, important than CO2. As a result I'll continue to be a sceptic on CO2 being anything more than a negligible player."

Please do!

Even if I was totally convinced it wasn't, the scientific method demands that we seek out well-informed, well-motivated sceptics to challenge the orthodoxy. I'm all in favour. It's why I partake in these threads.

All that's asked is that you try to keep an open mind, that you argue honestly, that you try to at least understand the opposing arguments before dismissing them, and that you're polite about not clogging up every thread on every topic with extended capital-letter rants on how you're sitting on the greatest scientific revolution ever and nobody is listening, as some do. :-)

"From my own perspective I really want to thank those people who have been posting here over the last week in particular. I really enjoy this unrestricted discussion which is all in good humour."

I enjoy it too. And you're welcome.

We know that CO2 concentration has an inverse logarithmic influence on any possible greenhouse effect.

Nobody seems to know the level above which the effect is negligable, we could be there now.

Surely it's a fairly simple experiment to get a rough idea of this in the lab?

"We know that CO2 concentration has an inverse logarithmic influence on any possible greenhouse effect. Nobody seems to know the level above which the effect is negligable, we could be there now."

I depends what you mean by "negligible". The logarithmic effect just means you get a fixed increase in temperature per doubling of CO2, as opposed to a fixed increase in temperature for a fixed increase in CO2.

So if you get x degrees going from 280 ppm to 560 ppm, you'll get another x degrees going from 560 ppm to 1120 ppm, and another x degrees from 1120 ppm to 2240 ppm, and so on. Obviously it slows down a huge amount, and you could argue that for every ppm you add the temperature rise eventually becomes "negligible", but it never stops. (Eventually the logarithmic relationship breaks down.)

So just decide how much of a change you're willing to neglect, pick an x, and calculate it. No need for a lab.

"The first is the logarithmic effect about which I agree with your assessment. It's equivalent to adding .5 to 1 then .25 to 1.5 and so on literally ad infinitum though for all practical purposes the series does reach 2 eventually."

That's not logarithmic, that's a geometric series.

Logarithmic is like 'the number of digits in x' as x counts up 1, 2, 3, 4, ... forever. The number of digits in x increases forever too - there's no limit - but it does so slower and slower.

"The other is the extent to which the relevant IR band becomes saturated at which point additional CO2 ceases to make a contribution to atmospheric temperature."

It doesn't matter if they're saturated or not. What matters is the average altitude of emission to space.

If you have a layer of completely opaque clouds 5 km up, then every band is saturated below that, and the temperature at the surface is 33 C warmer than at the cloud tops. If the clouds rise to 50 km, the surface temperature will be 330 C warmer than the cloud tops. The bands get saturated higher up.

And to lift the clouds to 50 km, you need more air. Since atmospheric pressure is roughly an exponential function of altitude (it would be exactly exponential if it was isothermal), then adding a given quantity of atmosphere leads to a logarithmic rise in its height.

Much of the mathematics was invented by the physicist/astronomer Karl Schwarzchild (of black hole fame) in his study of the internal structure of stars, and only much later cribbed by the climate scientists for application to planets - so I'm pretty sure it's still valid up to quite a large size of atmosphere... ;-)

Dung
I a great follower of "suck it and see" the worst that can happen is that it'll be removed. You can then report back.

I don't buy the average height of emission to space as a major factor. Obviously the theory looks good, in some sort of theoretical calm atmosphere. But what I can't understand, having read NiVs patient explanation many times, is how the temperature at some height in the 30,000ft range sets surface temp. The surface is where the energy becomes sensible heat. The surface temp sets the temp at altitude via (mostly) convection. But the surface temp, the air at 2m, has invariably just come from somewhere else. Thousands of miles away. The air just moves about too much, horizontally and vertically, for the emission/lapse rate to be much of a factor. Also, in the real world, convection doesn't stop. Warm air will always rise in cool air. And warm air has a couple of ways to get above the 50% emission level. Thunderstorms and mountain wave. That will be wet air, rising to over 40KFt in the tropics, loaded with energy which it can dump in the upper atmosphere. And the tropics is where it all happens. Exporting hot air up and sideways. What happens there is far more important than in milder areas because it will always dump energy faster at higher temps. Fourth power faster where radiation is concerned. The emission level/lapse rate illustration just doesn't get us anywhere. It relies on averages where they don't apply. It seems to misjudge cause and effect where the lapse rate is concerned. Surface temp (IMHO) sets the altitude via lapse rate. Temps at altitude do not set surface temps.