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Greenhouse warming 100 times greater than waste heat

What the science says...

Select a level... Basic Intermediate

Greenhouse warming is adding 100 times more heat to the climate than waste heat.

Climate Myth...

It's waste heat

"Global warming is mostly due to heat production by human industry since the 1800s, from nuclear power and fossil fuels, better termed hydrocarbons, – coal, oil, natural gas. Greenhouse gases such as carbon dioxide (CO2 play a minor role even though they are widely claimed the cause." (Morton Skorodin)

At a glance

There are various kinds of climate science deniers out there, but one grouping can usefully be classified under the acronym ABCD - Anything But Carbon Dioxide. These people appear to accept the climate is heating up. Flailing around to try and identify something other than CO2 causing the heating, they will seize upon all sorts of candidate causes. This is one of them. There are many others.

All the energy we use dissipates into the environment post-use, be it a driftwood fire on the beach or the heart of a busy metropolis, on the go 24-7. So it should come as no surprise that 'waste' heat does have a role - a minor one - in heating the planet. Humans have always been fond of fire since they learned to ignite things and there's nothing better than sitting round a blaze of a night with a few friends. No need to feel guilty about that. It's harmless in the overall scheme of things.

Waste heat is of course a much studied subject. After all, more sophisticated heating systems, compared to that fire on the beach, are energy-intensive and that translates as expensive. Ways to minimise heat loss and thereby improve efficiency form an active research topic. In that sense, a number of studies have looked at the bigger picture: just how much waste heat is there?

Unsurprisingly, cities, where huge numbers of people work, rest and play, are megacentres of heat wastage. The term, 'Urban Heat Island', acknowledges this. But the planet is a big old place and cities occupy relatively small parts of it. To find the warming contribution of waste heat, you need to have two figures: the total energy lost and the surface area of the planet. Doing the maths you can then derive the amount, expressed in watts per square metre. You can then compare it to other heat sources.

All studies of waste heat have arrived at a similar conclusion. There's a lot of waste heat over cities but the total, global amount, expressed as watts per square metre of the planetary surface, is a tiny fraction of the heating caused by the greenhouse gases. So while it's highly desirable to find better efficiencies in energy use and conservation, thereby saving money, when it comes to temperature it's greenhouse gas emissions we have to hold firmly in our focus. ABCD indeed. Next.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!

Further details

Heat is released to the atmosphere as a result of human activities, many of which involve combustion of fuels, directly or indirectly. Sources of this 'anthropogenic heat' include industrial plants, heating of buildings, air-conditioning, vehicle exhausts and many more. In cities, anthropogenic heat typically contributes 15–50 W/m2 to the local heat balance, and several hundred W/m2 can be reached in the centres of large cities in colder climates.

This heat doesn't just disappear - it dissipates into our environment. How much does waste heat contribute to global warming? There have been several studies over the years, widely-cited examples being Flanner (2009) (if you want to read the full paper, access details are posted here), Dong et al. (2017) and Varquez et al. (2021). All have come up with similar numbers despite differences in methodology: the core message is that while waste heat is an issue and is self-evidently undesirable, its contribution to global warming is a tiny fraction of that brought about by CO2.

Flanner concluded that the contribution of waste heat to the global climate was 0.028 W/m2. That was with respect to the mid 2000s. In contrast, the contribution from human-emitted greenhouse gases at the time was 2.9 W/m2 (fig. 1). So in the mid 2000s, waste heat amounted to about 1% of the total warming, with greenhouse gases making up much of the rest. The above numbers refer to radiative forcing, the change in energy flux at the top of the atmosphere. Or putting it in plain English, the amount of heat being added to our climate.

Relative radiative forcings due to waste heat and CO2.

Fig. 1: the relative radiative forcings due to waste heat and CO2 in the mid 2000s, from the numbers presented by Flanner (2009).

Since that time, both greenhouse gases and energy use have gone up (fig. 2), so it should come as no surprise to see increases in radiative forcing in both cases. Future projections have largely been focussed on recovery of the waste heat, such as that by Firth et al. (2019). An important conclusion of theirs is that, "full recovery of the theoretical potential is found to lead to a 10–12% reduction in the combined forcing of CO2 and waste heat over this period, mainly due to a reduction in CO2 emissions."

An important point to consider here is that the warming from thermal energy production occurs when a fossil fuel undergoes combustion. Whoomph! and that's that - the energy is produced in a single pulse then dissipates away. In contrast, warming from the emitted CO2 continues for the lifetime of CO2 in the atmosphere - potentially thousands of years (Zhang & Caldeira 2015). Zhang and Caldeira showed that "the energy released from the combustion of fossil fuels is now about 1.71% of the radiative forcing from CO2 that has accumulated in the atmosphere as a consequence of historical fossil fuel combustion." Again a small fraction of the CO2 radiative forcing, and emphasising the issue of the cumulative build-up of CO2 due to its relatively long atmospheric residence time.

Total energy use on Earth.

Fig. 2: total energy use on Earth, 1800-2023.

To conclude, greenhouse warming is currently adding some 60-100 times more heat to our climate than waste heat. That's not to say we should not be bothered about waste heat though, There are many sound reasons, including economic, for reducing heat wastage. It makes no sense at all to tolerate systems that for various reasons are grossly inefficient. But that needs to be considered as a separate entity from the huge problem of human CO2 emissions.

Last updated on 7 January 2024 by John Mason. View Archives

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Comments 51 to 75 out of 205:

  1. johnd writes: Ned at 22:36 PM, part of the issue being discussed was whether waste heat accumulates or not, and whether accumulative it's effect is more than negligible. There is no magic mechanism that removes heat from the atmosphere if it originally came from radiation but lets it accumulate if it originally came from combustion or whatever. IMHO these analogies to revolving doors and traffic jams seem to have no effect other than clouding the issue. How about some actual evidence, please? Doug B. gave a reference to a paper with quantitative comparison of the two sources way back in comment #2. That was very helpful, I think.
  2. Actually this thread is helpful because it's serving as a remarkably clear and concise example of how so much of this "debate" is ultimately driven by complete and total intractability on the part of some of the discussants. This is a very simple situation. "AHF" is capable of adding something like 1% of the quantity of solar heat being retained by additional impedance due to C02 and knock-on effects, working from mainstream estimates of anthropogenic GHG climate sensitivity. Just to make things clearer, let's imagine for a moment that we're somebody akin to Dr. Roy Spencer, a highly-qualified scientist able to make a start on articulating an alternate hypothesis to anthropogenic warming as an explanation for recent observed temperature increases. Under our Dr. Spencer-style hat, we believe that effective AGHG forcing is only 10% of more commonly accepted figures. In this circumstance we're looking at AHF forcing still being just 10% of anthropogenic GHG forcing. Even if we assume mainstream estimates are off by a full order of magnitude, AHF still pales in significance compared to anthropogenic GHGs, is still yet another order of magnitude less. Meanwhile, as has been pointed out, heat is mindless and does not care from where or to where it's going. Whatever heat is added to the pool here on Earth whether by anthropogenic liberation or arriving from the sun or for that matter emerging from retained and radioactive decay heat from within the Earth is going to find its way to the great beyond regardless of birthright, ultimately via radiation. Nothing about the origin of heat specifies its subsequent behavior. Heat flux from energy liberated as a part of human activity by any measure appears by all accounts to be a minor constituent of Earth's radiative energy budget. Even if one looks at the thermal impedance properties of the atmosphere from various outlier perspectives, AHF still does not measure up in a significant way. There's really not much to work with here for a so-called skeptic, to the point that one is left wondering how to speak patiently in the face of arguments to the contrary, once they've been repeated several times by the same person.
  3. There is one obvious problem with the whole "waste heat" argument which is this-why was there little to no measured warming between 1850 & 1900, given the amount of factories & power stations which were pumping out heat during this time? By today's standards, these factories & power stations were incredibly inefficient-meaning they gave off the vast bulk of their energy as waste heat. Yet strangely, in the last 60 years, we're expected to believe that waste heat generation is actually inversely proportional to improvements in thermal efficiency. i.e. the skeptics would have us believe that, even though thermal efficiency has improved over the last 60 years, the contribution of waste heat to global warming is increasing! That's *hilarious*. From my calculations, its fair to say that waste heat contributes somewhere around +0.006 degrees (& falling) to total global warming for the last 60 years.
  4. Another problem with the "Waste Heat" theory. Why did the planet continue to warm (due to increased solar activity) during the Great Depression, when industrial activity-world wide-fell, yet temperatures fell during the first decade of the post-war industrial boom?
    Response: Marcus, just to play devil's advocate on this line of argument, couldn't you likewise say "why was there no global warming during mid-20th century while CO2 levels were rising?" or "why was there global warming in the early 20th century while CO2 levels weren't rising that steeply?" :-)

    To fully address the question of waste heat during the industrial revolution and Great Depression, you would need to calculate the radiative forcing from waste heat over these periods. It's not that hard to work out - we do have figures on energy use over these periods (I link to the CDIAC data from here). Working this out is left as an exercise for the reader (eg - I'm too lazy to do it myself).
  5. I would hope that the term "waste heat" is not being understood simply as that portion of energy that is not delivered to the load. I can see how the word "waste might lead one to think this... thoughtout this discussion, I was referring to the broader concept. For say an automobile, waste heat should be understood as heat exchanged to cool the engine, the car's friction in all moving parts, the kinetic energy increase in the atmosphere left by drag, and combustive heat going out the tail pipe in the form of CO2 and water vapor. Similarly, house heating waste heat is not the percent of heat that escapes though a building's insulation, but every calorie used to heat the inside of a home or building; as this heat is eventually released into the environment. It is actually equivalent to the total worldwide energy consumption... 1.5 x E13 W Hope this helps.
  6. Marcus said "heat from within the Earth is going to find its way to the great beyond regardless of birthright, ultimately via radiation. " I agree 100%, but then you go on... "There's really not much to work with here for a so-called skeptic, to the point that one is left wondering how to speak patiently in the face of arguments to the contrary, once they've been repeated several times by the same person. " I have also asked more than several times how N2 and O2 radiate? I have still to see anyone acknowledge this difficulty. There have been some indirect responses about CO2 acting as an antenna! in which case, according to this explanation CO2 is helping to cool the atmosphere, and if this were the case, all latent energy would actually be attributed to waste heat. But lets not go there for now please. I would just like to see an explanation on how N2 and O2 (the non GHG portion of the atmosphere) are understood to cool radiatively, as I have been saying that they cant do this and will only generally cool by convection. And only by convection to "cooler" objects such as water and ice, implying a "selective" route for energy exchange. There was that question of why poles warm faster (for instance). At any rate Marcus, I also agree with your statement, "so much of this "debate" is ultimately driven by complete and total intractability"... This is obvious. I am not sure why, as we are all in the boat together.
  7. RSVP I believe we're all clear on that. Flanner is at any rate and since his number is the operative one here we're all on the same page it seems. One more time: AHF (Anthropogenic Heat Flux) is something like 1% of expected forcing from anthropogenic green house gases. As I explained earlier, estimates of AGHG forcing expectations could be too large by a factor of 10 and would still dwarf AHF. "There's no there, there." Meanwhile you still seem to be worrying over the relationship of N2 and O2 w/waste heat. It's not a unique or special connection. Ned explained the commonality here.
  8. doug_bostrom I went there and (as before) read... "Likewise, most of the heat from GHG absorption will also be transferred to O2 and N2 molecules, thanks to the fact that each CO2 molecule collides with N2 or O2 molecules roughly one billion times per second." On the one hand, the more you defend CO2's efficiency in transferring energy, the less significance you are actually attributing to the effects of CO2 concentration level.
  9. RSVP #58 "On the one hand, the more you defend CO2's efficiency in transferring energy, the less significance you are actually attributing to the effects of CO2 concentration level. " Ummm. No. These are two separate processes that are physically independent. Your logic is wrong, and your physics is deficient.
  10. RSVP #30, no you really didn't answer my questions - but hey, why not; 1: No. 2: Same as all other heat... it radiates at equal intensity in all directions. 3: "energy dissipation" is two words... and two words neither you nor I have used. Ergo, it is impossible for me to determine what meaning they are meant to have "in this context" because there is no context. 4: Same as all other matter in the universe... they absorb some wavelengths of EM radiation and allow others to pass through. Absorbed radiation is (per issue 1 above) then re-emitted, though possibly at a different wavelength. 5: The wavelengths involved are different. Specifically, Nitrogen and Oxygen are largely 'transparent' to the infrared wavelengths emitted by the planet's surface while GHGs are not. BTW, your hypothesis seems to depend on a belief that waste heat 'goes into' N2 and O2 and stays there (which is completely wrong) while solar heat somehow avoids those two elements. Which is, of course, pure nonsense.
  11. I agree 1000% with Doug Bostrom's comment up here, both in terms of the substantive issue and the reflections on the context that Doug offers in the first and last paragraphs. There is nothing wrong with having people come here and ask basic, even naive, questions. Like Doug, however, I am uncertain about how we as a community should respond to someone who continues to make the same fundamentally wrong claims over and over again, running over all explanations and corrections like an implacable bulldozer of willful ignorance. We have seen this before with other commenters (e.g., a certain commenter in this thread). Most of the people who comment on this site do so in good faith, with the expectation that their efforts to promote understanding won't be wasted. The presence of a commenter who is more or less impervious to reasonable discussion and the mutual sharing of ideas throws a large spanner into the works.
  12. I thought I would give RSVP a try. Essentially all of the IR from the surface is absorbed by CO2 in the atmosphere and is not radiated directly into space. (Your example of 5% absorbed is incorrect). You would not see lights in fog, you would see an evenly lit background. When CO2 absorbs IR energy, it transfers most of that energy as heat immediately to the surrounding N2 and O2 by collisions with those molecules. Waste heat is absorbed by the atmosphere (primarily O2 and N2) in various ways. Once the atmosphere absorbs heat, from any source, it is all treated the same. -->The N2 and O2 transfer their heat back and forth with the CO2. The heat is transferred around the atoms of the atmosphere (primarily by collisions) and eventually comes to another CO2 molecule. It is then re-radiated as IR. Some IR goes up and some goes down. By chance, after a long path with many absorbtions and re-emmisions, the IR is emmited into space. Increasing CO2 causes the path the heat follows from the Earth into space to be longer and heats up the atmosphere. Since the amount of waste heat is 100 times lower than heat from GHG, it is not significant. Do you have any questions about this explaination?
  13. Michael Sweet: Increasing CO2 causes the path the heat follows from the Earth into space to be longer... Somehow I've not seen the process described quite that way before. Delayed by rerouting, balance only restored as emissions and collisions become sufficiently frequent as to overcome the delay, leaving the atmosphere more stuffed with activity or that is to say warmer. Thanks! Also thanks to RSVP for forcing Michael to produce that model. Others probably already had it in mind, me not in quite such a succinct way.
  14. michael sweet at 08:12 AM on 28 July, 2010 said.. "By chance, after a long path with many absorbtions and re-emmisions, the IR is emmited into space. Increasing CO2 causes the path the heat follows from the Earth into space to be longer and heats up the atmosphere". I have a question if you'll permit me. IR photons travel at close enough to the speed of light, (about 300,000km per second). With that in mind, do we know HOW LONG this delay you are talking about is? And how does it relate to the rate of cooling observed overnight?
  15. Baa Humbug - The transit time of a photon in flight isn't going to be very long; but the number of absorption/emission events will certainly increase. Each absorptio/emissionn takes some time, with a probability of transferring that energy to other gas molecules instead of re-emitting; each emission (from the same GHG molecule or another one excited to emit by the thermal state of the air mass) takes some time as well. So longer transit distance = more absorption events = more chances to heat the air rather than just being re-emitted.
  16. Baa Humbug: I would say the same as KR. Keep in mind that a single photon does not make the whole path, this is a simple model. If the path is longer, with most of the time spent absorbed by a molecule, it will take the heat longer to escape. The speed of the photon does not matter. When the path is longer for heat to escape but the source of heat (the sun) stays the same that means heat accumulates in the atmosphere. I am sure that the time delay could be calculated, but what scientists find useful is the forcing. Cooling overnight is a different process. The time for the heat to escape is longer at night with more CO2 just like during the day. The situation is complicated by water but the essential details are the same.
  17. I couldnt get the full version of Flanner 2009, so I cant see how he concluded that waste heat is so small relative to GHG forcing. I have a “burning” question. I lit a small pile of logs under last night’s moon, enjoying the fire’s warmth and watching sparks and smoke convecting towards the cosmos. Amongst the smoke was some of that awful carbon pollution, and I wondered about the heat that could be added to the planet from CO2 if it had a residence time of say 1000 years. How did the GHG forcing energy compare to the energy released by the simple exothermic oxidation of the photosynthesized ligno-cellulosics (aka fire) ? I made my own calculations about this (below), and then looked around the web until I found the topic thread here about waste heat vs GHG forcings. I’ve read through this thread and Flanners 2009 abstract (couldn’t access the full paper) which says that waste heat is small (1%) compared to GHG forcing.... quite the opposite of where I got to. So have I calculated wrongly ? Why are my conclusions so different to Flanner? Here is my reasoning.... Assumptions 1.A tonne of burnt coal (78% carbon) releases 2.86 tonnes of CO2; the energy content of coal is about 24MJ/kg 2. About half of CO2 from current annual hydrocarbon burning ends up back into the biosphere and the oceans, the other half stays in the atmosphere. 3. Atmospheric CO2 has a residence time in the order of centuries 4. Doubling CO2 is like adding the equivalent of 3.7W/m2 warming energy, around the clock. 5. If atmospheric CO2 is doubled, eg from 290 to 580ppmv (ppmv * ~1.5 = ppm by mass) , then atmospheric mass of CO2 goes from 2350 to 4700 Gt ( 10^9 tonnes). (nb. Annual hydrocarbon-derived CO2 emissions are presently about 30Gt/yr, historically we have released about 1200 Gt hydrocarbon-derived CO2 since 1850 (of which 400Gt since 1990) , and atmospheric mass of CO2 has increased by about 800Gt since 1850 (current mass 3150 Gt). I thought it would be easier to deal with some human-scale measures here, so converted as follows: If we allocate CO2 mass evenly across the surface of the Earth (5.1×10^8 km2), that means that the atmospheric column above each square metre contained about 4.6 kg CO2 in yr 1850 (290ppm). Doubling CO2 thus means adding another 4.6kg/m2, so at the ratio of gas:solid of 2.86:1 and with only about half of the CO2 staying in the atmosphere, doubling CO2 from 1850 concs would require burning about 3.2 kg of coal-equivalent for every square metre on the planet. From point 4 above, the additional 4.6kg of CO2 produced by burning 3.2kg of coal leads to 3.7W x 24 hours x 365 days = 32.4Wh per year. Watts and Joules can be converted as follows...a Watt is a unit of power which measures how fast energy (measured in Joules) is converted, 1.0W = 1.0 J/sec, so 3.6kJ = 1.0 Wh. So; from 1. above, Burning 3.2kg of coal liberates 77 MJ of energy (3.2 x 24) , and from 4. above, the energy “forced” into the climate system by adding 4.6kg CO2 which stays there for 660 years , is 32.4Wh/yr x 3.6kJ/Wh x 660yrs =77 MJ. In other words, the energy from burning a piece of coal (“waste heat”) is equal to the GHG forcing energy of the CO2 created by burning, if and only if the CO2 stays in the atmosphere for 660 years. It seems that greenhouse warming in the short-term (eg decades) is therefore only a miniscule fraction of the actual combustion energy released. To me this conclusion begs the question, if it takes 660 years for the greenhouse heating energy to be the same as the energy released by burning, how come we aren’t already more than toasted by the simple act of combustion itself? And where is all that heat from the fires going? In one year, it’s 660 times as much as the GHG forcing energy, quite the opposite of what Flanner 2009 said. If the waste heat from combustion is not staying in the atmosphere (or oceans), why would the early-evening near-ground greenhouse warming be any different?
  18. hillbilly#67 : "where is all that heat from the fires going?" The surface of the earth radiates at 288K (~14 C); suppose your fire burns at 400C (673K). The radiated power varies with the 4th power of temperature (in K); there's a huge difference between 2884 and 6734. So the short answer is hot objects lose energy as infrared radiated to space very rapidly. See recent IR photos of wildfires (example here). See the Stefan-Boltzmann law wikipedia article for a reference.
  19. Thanks Muon, The IR photos and S-B ^4 were helpful explanations for my small open fire, but you are really referring to temperature, not heat energy. I can think of two situations where the temperature is lower and the explanation may not hold. For example I can cover or contain the fire, or make it burn very slowly. The waste heat from a coal-fired power stations CFPS is ultimately equal to the energy content of the coal. It just comes out in various forms, steam from condensation towers, cooling water re-circulated in dams, the walls/roof heated by boiler radiation, transmission resistance in lines, and finally the actual electricity produced that goes into lighting or electric motors or whatever, all of which give off some low grade heat. So most of that waste heat from the CFPS is in fact similar to the background and would therefore seem to have as much chance of being absorbed by CO2 (or H20) as the night time losses from the natural land/water surface. And what if the coal was burnt very very slowly? For example, like a rotting log. Suppose it takes 10 years to decompose the 3.2 kg of coal in my first question. The heat (energy, not temperature) liberated by oxidation is still 24 MJ//kg, and it will still take 660 years for the warming produced by GHG emission to equal that amount. (assuming CO2 is already doubled so it has the effect of warming at 3.7W/m2). So it seems if you take out the rapid IR loss, the conclusions from my fire analogy still stand. The GHG warming energy from the emitted CO2 (in the short term) is a miniscule fraction of the energy released by combustion. Why is that GHG warming energy (night time only , near ground) not lost from the system as easily as the combustion energy?
  20. hillbilly#68: "you are really referring to temperature, not heat energy." You asked about the heat from your fire, a high temperature source. But the real question is indeed the comparative quantity of energy -- and a daily average of 250 W/m^2 across a verrry large number of m^2 represents a lot more watts than fires, power plants and cars. Hence the waste heat = 1% of GHE conclusion. You're coming to this thread quite late; I suggest you review the prior comments here as well as the 400+ comment thread Waste heat vs. greenhouse warming. One of the key questions raised there was this: why the continued warming during times of economic downturn when waste heat input declines?
  21. mullumhillbilly @67, accepting your figures for the sake of argument, I come to your calculation of the energy input from the greenhouse effect. Specifically, adding 4.6 Kg per m^2 atmospheric CO2 (doubling from pre-industrial levels) results in an a forcing of 3.7 W/m^2. 3.7W/m^2*(60*60*24*365.25)seconds = 116.76 MegaJoules for a single year, not the 77 MegaJoules for 660 years that you calculate. The error appears to be where you write:
    "From point 4 above, the additional 4.6kg of CO2 produced by burning 3.2kg of coal leads to 3.7W x 24 hours x 365 days = 32.4Wh per year."
    In fact, 3.7 *24 * 365 = 32,412 WattHours, not 32.4 has you calculate. Returning to the correct value, by your corrected estimation burning 3.2 Kg of coal per m^2 of the Earths surface would release 76.8 MJ/m^2, which would rapidly dissipate. The CO2 from that combustion would have a forcing of 111.76 MJ/m^2 per year for 660 years, or 73.7616 GigJoules, or 960 times the amount. This in fact underestimates the effect of the greenhouse forcing for it does not take into account feedbacks, which increase the amospheric forcing of the CO2 to 8 to 10 W/m^2 (sorry, don't have the exact figure to hand). That at least doubles the effect. As you can see, by these back of the envelope estimates, the estimate in the article above estimate is conservative by a factor of 100. This is because it compares current greenhouse forcing with current annual non-renewable energy production, and does not include the life time effects of CO2.
  22. Correction to 71: where I said conservative by a factor of 100, that should be by a factor of 10.
  23. OK thanks Tom@71, I accept that correction to my arithmetic. So in fact the GHG energy effect is equal to the combustion energy in just 0.66 years !! (32.4kWh/yr x 3.6MJ/Wh x 0.66 yrs =77 MJ). That's just as wierd from the opposite end, hundreds of times more energy from the byproduct than in the combustion ??! BTW I thought the 3.7 W/m2 per doubling did already account for the feedbacks (at present with 0.33 doublings, it's 1.66W/m2 incl all feedbacks?) IPCC AR4 Fig 2
  24. Muon @70 Here’s a thought experiment. It doesn’t require believing that the atmosphere behaves literally like a greenhouse. Suppose we have two identical glasshouses a few metres apart, each of them with 70% floor area covered by water (let’s say a metre deep ie a large heat sink compared to the remaining area of lightly gravelled dry floor). Further suppose this is a special kind of glass which is completely transparent to all radiation wavelengths. By day, the doors are opened and the roof is vented so air and surface temperatures and humidity are same as the surroundings. All vents closed at sunset, and one glass house has extra CO2 added (at ambient temperature) so that it has say 256x the concentration of the other (8 doublings). Surplus air is vented so that pressure is also constant. Heat energy within the enclosures is equal at the start of the night. Then as the night cools, heat in the form of longwave infra red radiation LIR is emitted from the ground and the water. So what happens to the temperature and heat energy vs time profiles in the two glasshouses? What I think will happen is this. In the CO2 enriched state, more of the outgoing LIR is intercepted and re-radiated. Some of the re-radiation leads to (i) collisions with N2 and 02 thus raising the air temperature (kinetic energy) and (ii) greater evaporation and higher water vapour content in the air. So a temp-vs time and heat energy content vs time chart of the CO2 enriched state would show slower declines than the ambient air state. However both greenhouses are ultimately losing their heat to the surroundings. If kept in the dark for long enough, they will both fall to the same temperature in equilibrium with their surroundings. So, the key question here is how long does it take for the two glasshouses to get to the same temp and contained energy state? The area between the two temp-time or energy time decline curves is the quantum of GHG warming. If we measured temperature on a minute-by-minute basis through the night, we’d find that the “average” temperature has increased in the CO2 enriched glasshouse because the early evening temperature is higher for a period. However if we only measured overnight minimum and daily maximum, then provided the time to cool to equilibrium was less than 12 hours, there would be NO apparent difference between the two. The enriched system still returns to the same overnight minimum as the control, it just gets there a bit more slowly. Is this what is happening in the atmosphere (and oceans)? If the energy states equilibrate overnight, then average temperature has increased because of the early evening slower decline of the curve, but climate HAS NOT CHANGED because ultimately the energy states of the control and enriched systems are at the same point each morning sometime before dawn. The CO2 enriched system has not “gained” any energy to be carried forward (in say the water bodies). Over the long term, we would see NO energy gain in the enriched system, even though we have observed a rise in average temperature. With no accumulating energy gain, there is nothing to drive the hurricanes, floods, droughts, heatwaves, snow dumps, melting ice etc etc. Can anyone point me to a paper which shows empirically that overnight heat energy loss from the Earth’s atmosphere does NOT equilibrate before dawn, so that energy is actually accumulating in the system (and thence “climate change”) ?
  25. mullumhillbilly @73, it does indeed sound weird, but only if you think of the CO2 as providing the energy. In fact it doesn't, rather it helps retain the Sun's energy more efficiently, and that retaining the Sun's energy more efficiently should retain more energy at the surface than is generated by a coal fire is not weird at all. The IPCC figure shows only forcings, not feed backs. The difference is that the effect of a feedback is a function of temperature in the short term, as for example with the water vapour content of the atmosphere. In contrast, industrial production of aerosols, and aircraft contrails (as two examples) are not a function of temperature in any meaningful way.

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