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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 26 to 50 out of 205:

  1. CBDunkerson #22 "1: Why are temperature increases most pronounced at the poles... where there is virtually no industry generating waste heat? ------------------------------ This gets back to the issue of how N2 and O2 dissipate heat. Not by radiation. Since energy cant be destroyed, it must be spreading itself everywhere. 2: Why do we not see huge spikes of increased heat around urban industrial centers gradually leveling off as you get further into non-industrial regions? ---------------------------- answer to 2.: We do. See links. 3: Why has warming been most pronounced at night and during Winter? That makes sense if the warming is due to decreases in the rate heat escapes... but not if it is due to increasing 'accumulated heat'. --------------------------- The idea that N2 and O2 are not good emitters of IR agrees with your statement about "decrease in the rate heat escapes". The difference here is in what we assume is causing this. In addition, for a fixed quantity of man-made heat, the lower the temperature, the higher the percentage this represents quantitatively relative to the ambient energy level, and convective heat transfer is in proportion to the difference in temperature. So this also can be applied to answering in part question 1. And I dont know about you, but I personally use more heating oil in the Winter. 4: Why is the stratosphere cooling? Again, that makes sense if heat is being prevented from escaping to the stratosphere... but not if the total heat of the planetary environment is increasing." ----------------------------- Is it really cooling? Obviously this is not based on tree ring data. ;)
  2. RSVP - I see no no numbers in your latest post, no evidence. All you present are "it seems like it should..." statements contradictory to what we observe. The numbers, the measured values, and the physics all say you are incorrect about the importance of waste heat. A hypothesis must be congruent with the evidence. If a hypothesis is contradicted by all the evidence, it's time for a new hypothesis. Waste heat driving global warming just doesn't make sense, RSVP. And you have proved exactly zero evidence to support that hypothesis.
  3. RSVP #26 1: Your answer makes no sense. Heat spreading through atmospheric Nitrogen and Oxygen does not explain why the poles are heating faster... there is not more Nitrogen and Oxygen there. 2: Your answer is clearly false. Yes, the Urban Heat Island effect (which has very little to do with waste heat) causes cities to be warmer (though nowhere near enough so to explain the GLOBAL temperature increase), but it does not result in warming of the rural areas around these urban centers as we would expect if global warming were simply the spreading out of heat from urban sources. Hence the 'island' part of the name... it is a sharply localized effect. 3: Again, your answer makes no sense. How are atmospheric Nitrogen and Oxygen responsible for a decrease in the rate of heat escape? Especially as they have not themselves changed significantly? As to 'more heating oil in Winter'... I thought you had claimed that measured warming was due to ACCUMULATED waste heat because it is magically prevented from escaping the atmosphere. Thus, when the heating oil was burned is irrelevant... the heat should still be there in the Summer. 4: Here you seem to simply deny the data.
  4. Previous comment, last sentence - that should be *provided*, not *proved*; I believe that makes more sense. ...must...practice...typing...
  5. CBDunkerson I have tried to answer your questions. It would seem fair that you try to answer some of mine. 1. Can energy be destroyed? 2. Where exactly does the Urban Heat go? 3. What does the word energy dissipation mean to you in this context? 4. What are the radiative properties for cooling of N2 and O2? 5. How do these properties differ from GHGs?
  6. RSVP, I'm (honestly) still uncertain about what point you're making. I -think- you're saying that observed increases in global temperature are significantly affected by anthropogenic liberation of heat energy. If that's the case, your argument is stuck here Nearly all energy used for human purposes is dissipated as heat within Earth's land–atmosphere system. Thermal energy released from non-renewable sources is therefore a climate forcing term. Averaged globally, this forcing is only +0.028 W m−2... until you can provide a substitute number for Flanner's calculated result that is both much larger and more correct. If you're driving at something else, different matter of course.
  7. RSVP, you could simplify this whole process a lot if you would just point us to a paper, a study, or anything, really, that quantitatively shows waste heat being equal to or greater than radiative forcing from GHGs. Once we have such a source, we can debate the data, methods, interpretations, etc. But until you give us something that at least remotely resembles a shred of evidence, what's the point?
  8. N2 and O2 are transparent to IR. These gases do not radiate since they are not GHGs, and therefore have a hard time loosing their heat outside of convective cooling with water and ice. The cooling of manmade heat engines raises the temperature of N2 and O2 directly. This heat is carried around the planet and is being discharged and dissipated in the cooler regions since convection requires a lower temperature for heat to be transferred.
  9. I think we can conclude that this is a dead end, unless RSVP can produce a number for "AHF" more useful and much larger than Flanner's.
  10. N2 and O2 are transparent to IR. However, the CO2 and H2O content of the air mass can and does absorb and emit IR. GHG's at air temperature will lose/gain energy as they emit/absorb IR, and through molecular collisions will cool/heat the air mass as a whole, including the N2 and O2. And that thermal exchange is very efficient, very fast. The air mass as a whole, containing GHG's, is not transparent to IR - it heats and cools depending on the IR in/out balance. What exactly is not clear about that?!? I've got nothing more to say here, unless RSVP comes up with a measurement supported number comparable to Flanner's.
  11. RSVP, the point that Doug and KR and I keep emphasizing is the main one -- you need to provide some evidence here. But aside from that, I admit I'm confused by all the references to N2 and O2. Why do you think there's some kind of distinction there? Most of the waste heat from anthropogenic sources will be carried in the atmosphere by O2 and N2. 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. Perhaps you're under some misimpression that when a greenhouse gas absorbs IR radiation it only raises the temperature of the GHG molecules themselves? If so, that's wrong. The atmosphere is not a mix of gases each with its own distinct temperature.
  12. KR "The air mass as a whole, containing GHG's, is not transparent to IR - it heats and cools depending on the IR in/out balance. What exactly is not clear about that?!?" The crux of the AGW theory (and the campaign to control GHGs concentrations) rests on the assumption that the efficiency of "The air mass as a whole" to "emit/absorb IR" is a function of concentration. Making this kind of a blank statement about how air gets rid of heat ignores the premises upon which AGW is based on.
  13. Ned "I'm confused by all the references to N2 and O2. Why do you think there's some kind of distinction there? " What makes a GHG a GHG? N2 and O2 are not greenhouse gasses by definition, otherwise the atmosphere would be 100% GHG and there would be no problem with emission of GHGs. How can you ask this question?
  14. Ned "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. " Why does GHG concentration matter? Does it go to two billion times per second as concentration doubles? My point is you make it sound like all the energy captured by CO2 goes directly into the surrounding molecules (one minute), but concentration "modulates" this process another minute when it comes to justifying the reduction of GHG emissions.
  15. The concentration of CO2 in the atmosphere affects the absorptance of longwave IR. It doesn't particularly affect the rate at which the energy from that absorption is shared with the rest of the atmosphere. Those are two entirely different processes. You really don't understand how this works, do you?
  16. Maybe this will help. RSVP, think of each individual CO2 molecule as a tiny machine, taking in fuel (IR radiation) and giving off waste heat (vibrational energy transferred by collisions with other molecules in the atmosphere). Every year, we add billions of tons of those tiny machines to the atmosphere. The waste heat they produce is two orders of magnitude greater than the heat from our clunky mechanical devices down here on the surface. Does that help?
  17. In the medium concentrations we have for GHG's in Earth's atmosphere, a doubling of CO2 concentration increases the width of the blocked LWIR band enough that the Earth's surface must be 1oC hotter for the integrated spectrum at the top of the atmosphere to sum to the energy coming in. Increased GHG concentrations slow the escape of the LWIR energy from the atmosphere. The 10^9 collisions/second ensure that the GHG's maintain the same temperature as the rest of the air mass - you can't separate N2 and O2 temps from the air mass as a whole, and it's rather silly to claim so. Back to the point of the thread - Human energy use releases energy at a rate 2 orders of magnitude less than the GHG entrapment. Unless you provide some evidence to the contrary, which you have not done so far, waste heat is not an issue worth worrying about.
  18. Here's another summary on this topic, with some references: Global Warming Waste Heat
  19. An metaphore to "queue threoy" may help you all... There is a highway that goes into the city. The flow is constant everyday (no weekends in this theoretical land). The flow of cars depends on the amount of traffic since the channel (the highway) but in generally is usually constant and flows well. One day Road Maintenance needs to paint the lines on the side of the highway and places cones on the right lane. This slows traffic down slightly. (This might be effects of elevated CO2... perhaps). On top of this however, there is a special event that day (rock concert) and the number of cars increases, but only by 1%. (waste heat) Since the flow was basically optimal before these two occurrences came about, the traffic almost comes to a complete halt. There is now a traffic jam and cars are moving bumper to bumber. Someone in a car wants to see a huge accident to justify this inconvenience. As he passes the cones, he is dissappointed that there is nothing dramatic to see. (AGW guy, asking me for numbers to justify the effects of man made waste heat).
  20. RSVP, imagine that as cars from the rock concert move down the congested highway the mayor of the local city connected to the highway announces that an asteroid is approaching and will strike the center of the city within hours. Many residents respond to the announcement by "getting out of Dodge," ironically jumping into their Dodge automobiles and hightailing it for the proverbial hills. Proportioning the public panic to the relative numbers of AHF forcing versus forcing by a doubling of C02, the highway must then cope with not only the increase of traffic from the concert but a panic stricken flood of drivers representing over 100 times more additional vehicles beyond that created by the concert traffic. Not to put too fine a point on it, you're obsessing over a very tiny number.
  21. RSVP - queuing theory, with its associated transition points at certain flow rates, has absolutely nothing to do with this topic, and can only be considered an (rather poor) attempt to change the subject. Your waste heat issue is 1% the effect of GHG entrapment, negligible in comparison. You have shown no evidence whatsoever to the contrary. This is a science blog site - Appeals to Belief and Red Herring logical errors really don't hold up to actual numbers or physics.
  22. Also take a look at Common Sense error, strongly related to the Dunning-Kruger effect
  23. 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. Obviously if the total heat losses from your dining room, being well insulated one hopes, remains less than that being provided by the burning candles, then it is the total accumulated heat that is relevant in any quantitative comparison at any point of time. Naturally, if at some point of time someone opened a door introducing a period of increased heat loss, that is a period of cooling, then a portion or perhaps all the accumulated heat of the burning candles would be lost.
  24. RSVP at 06:35 AM, perhaps another analogy may help. A well designed and up to date maternity hospital has been built and access is via a revolving door that is designed to maintain an efficient environment and minimize heat losses by operating only with one person entering and one person leaving at the same time. Only 1% of those entering the hospital do so to give birth, the bulk of those entering, and leaving are visitors or staff. At what point does the hospital board have to go back to the engineers who did the original design calculations, and ask them if the assumption they made that as only 1% of those entering the hospital were pregnant, and so could be considered negligible, was a indeed a valid assumption?
  25. johnd - False distinction logic error: thermal energy is thermal energy, none of it is 'pregnant' or otherwise distinguishable from the other. This is akin to the G&T arguments where some skeptics thought that an object would somehow 'know' that certain photons came from colder objects, and would not therefore contribute to energy balances. Photons (and joules) don't carry ID cards, unlike Arizona citizens. Thermal energy gets distributed by the usual suspects - conduction, convection, latent heat, and radiation, with radiation measured to be the dominant pathway. The source of the energy is irrelevant to how it leaves. As per the thread, however, only ~1% of that thermal energy comes from energy usage, the other 99% comes from GHG entrapment of solar energy. Bad analogies don't change that. If nothing else, this thread has been a delightful example of logic errors...

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