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Is air conditioning making cities hotter?
- rapnie 3y ago[flagged]
- deleted 3y ago[deleted]
- merth 3y agoinstall "ublock origin" and enable "annoyances" from settings.
- SoftTalker 3y agoDidn't know about "Annoyances" thanks -- giving that a try now (these are under the "Filter lists" tab in settings, for anyone looking for them).
- MaKey 3y agoThanks for the hint!
- GLjEI4YbnGD27LB 3y agoThanks, also didn't know about annoyances!
- guerrilla 3y agoThat would seem inevitable, so the only real question was how much (+2C.) So, how much cooler does the city with many heat pumps get in the winter then?
- stephen_g 3y agoThe opposite effect I expect should be less for heating, since the heat is constantly leaking out of buildings at some rate back into the environment (insulation, double glazing etc. reduces this but all the added heat eventually leaks out), and additional energy is being put in which turns into heat too (e.g. COP 4 means 1 unit heat from electricity and 3 units shifted from the outside environment). So whether there is temporary localised cooling depends on the quality of the insulation but overall and over time there is no cooling due to the additional input.
- guerrilla 3y agoThe heat is constantly leaking into the buildings too. I'd be more concerned with differences in efficiency with direction that you mention at the end. In any case, the net result is still negative, so how much negative is still the question that stands.
- Ozzie_osman 3y agoEffect must be less. For AC, you're transferring indoor heat outdoor AND generating excess heat from running the AC itself. For heating, the excess heat generation presumably works counter to the heat transfer.
- raverbashing 3y agoGood question, some aspects make it different: - you're always getting some "free warmth" through the sun, so on average you need to pump less energy to heat than to cool (for same temp difference) - Hot air rises, cold air sinks, not sure how that works in a city environment, probably concentrates the cold more
- superq 3y agoTemp differentials are still differentials, though, so sun warmth would be already accounted for.
- raverbashing 3y agoKind of, because your house will always be warmer than the outside at thermal equilibrium, both in summer and winter (with heating/ac off) So, yes if you consider the differential in-house current-target temperature yes, but difference of outside/inside temperature no.
- grey-area 3y agoFor the curious, the answer is yes, by 2.4 degrees C.
- aaron695 3y ago[flagged]
- matthewmacleod 3y agoThe article you have linked to literally contains the phrase "Air temperature is increased by up to 2.4°C" citing the conditions under which this was observed. Have I completely misunderstood what you are trying to say?
- enraged_camel 3y agoCheck their comment history. It's mostly flagged comments for a reason.
- pierat 3y ago"Up to" is Comcast weasel words language, in which -10c is also in that set. It's at best garbage science reporting. Best answer: give GIS heatmaps that show variance of temp from in-city to nearby large green space. Then we can talk. (I see the urban heatisland effect locally. But 1 instance isn't science. Doing the math AND displaying it correctly is.)
- aaron695 3y ago[dead]
- jiofj 3y ago[flagged]
- reportingsjr 3y agoThis is one reason I heavily push for roof top solar, even if it is a bit more expensive than utility scale. In many areas air conditioning is pretty much a given at this point. A typical solar panel absorbs ~20% of the sun's energy blasted on to a city rooftop. If that's used to power air conditioning it's doubly effective. You're reducing the heat urban heat island effect from the sun's energy, and you're also not adding additional heat from external power sources in to the city. On a large scale this would really help make cities more livable. On a hot summer day here in northern Kentucky I noticed a massive difference (I've roughly measured it at a 5-7F difference) going from less developed areas to the more urban areas.
- guerrilla 3y agoWhat % do trees and other plants absorb?
- reportingsjr 3y agoBelow 10%. The most efficient plants are food crops we've genetically modified. I believe corn absorbs around 10%. However, plants also reflect a lot of energy, unlike black/asphalt roofs that most people in the US install.
- guerrilla 3y agoWhen you say efficient it makes me suspicious. Just because a plant doesn't absorb the energy for conversion doesn't mean it doesn't absorb it as heat. Remember, they're quite connected to the ground so they could be good heat dissipation (I have no idea, just speculating.)
- tonfa 3y agoOne thing trees/plant help with (instead of concrete/asphalt in cities) is with the added impact of evapotranspiration (besides providing shade).
- ars 3y ago
- arnaudsm 3y agoGreat example that systemic problems require systemic solutions. AC is an individual solution to global warming, and actually making things worse. And deincentivizes us from fixing the actual problem.
- whynotmaybe 3y agoLike this? https://www.theonion.com/addressing-climate-crisis-bush-calls-for-development-o-1819569191 https://www.theonion.com/addressing-climate-crisis-bush-call...
- megaman821 3y agoWell if AC is your cutoff line for the amount of energy use and carbon intensity making things worse, I have really bad news for everyone using heating.
- baobabKoodaa 3y agoMaking things worse? What? AC saves lives.
- tonfa 3y ago> Air conditioners [...] leak harmful planet-warming gases into the atmosphere. Anyone has a reference about that? Last time I tried to research it, it seems like it was mostly fixed at least in Europe with the most harmful gases being banned for new sales.
- moritz 3y agoThe phase-out under the Montreal protocol is an ongoing process, but we are far from there. The HFCs that replaced (H)CFCs in the 90s quickly turned out to be fastes growing category of short-term climate pollutants in many countries in the world [1]. The Kigali Amendment to the Montreal protocol from 2019 now covers HFCs too, and the EU limits them since 2015, but these things take time… R-410A, commonly used in Europe, has a GWP of 2088. Worldwide, R-22 still is the most common refrigerant. That’s a HCFC, so stratospheric ozone depleting, and with a GWP of 1960. [1]: https://www.science.org/doi/10.1126/science.1216414 https://www.science.org/doi/10.1126/science.1216414
- stephen_g 3y agoR-410A is being phased out in major markets including the US too over the next few years (R-22 has been banned for new equipment most places for more than a decade, and is banned entirely in the EU since 2015 for recharging existing units). My Mitsubishi air to air heat pumps (one from 2015 and one from 2018) were already R-32 (GWP 675, Ozone depletion potential 0) and my air to water (Sanden, installed 2022) is R-744 (which is CO2 - obviously GWP 1)
- tonfa 3y agoThanks both for the pointers (it's easier to google if you know what to search for). https://climate.ec.europa.eu/eu-action/fluorinated-greenhouse-gases/climate-friendly-alternatives-hfcs_en https://climate.ec.europa.eu/eu-action/fluorinated-greenhous... is the list of alternatives with corresponding GWP for EU.
- moritz 3y agoIn so-called developing countries, the full ban of R-22 will be 2030, which is a full ban with an asterisk to 2040. Not saying the phase-out isn’t happening, but there are, and there will be for quite some time, millions of units leaking climate pollutants (which was the question).
- ajb 3y agoI've been looking at getting shutters on my windows; They're not common in the UK but are common in more southern European countries. Unfortunately UK windows are designed without the expectation that shutters might be installed. Also it seems to require planning permission to install them on street facing windows too, as they are not currently one of the exceptions. But installing air conditioning (and heat pumps) does have an exception. This needs to be fixed.
- jdjdjdjdjduuuu 3y ago[flagged]
- ajb 3y agoI don't know if that is a joke, but shutter != gutter. A shutter covers the window during hot weather to keep the sun out and keep the building cool, and can be opened during cooler weather. The relevancy is that unlike air-conditioning they don't consume power or heat the surrounding city.
- kraig911 3y agoA lot of things are making everything including cities hotter. Here in Texas it was 110 at my house yesterday in September. I live way way way outside of a large city. I personally think concrete/asphalt absorbs and retains a lot of heat keeping things hotter. If we could just reflect more back I think it'd help much more. I have solar on my house and it practically pays for my AC Bill.
- stephen_g 3y agoConcrete and asphalt definitely do absorb huge amounts of heat - it’s well studied and called the urban heat island effect.
- zo1 3y agoDo we know how much of that is causing global warming?
- s0rce 3y agohttps://www.nature.com/articles/s41467-022-31558-z https://www.nature.com/articles/s41467-022-31558-z
- Solvency 3y agoYeah. Read a book. https://www.amazon.com/Kiss-Ground-Reverse-Climate-Ultimately/dp/1501170252 https://www.amazon.com/Kiss-Ground-Reverse-Climate-Ultimatel...
- stephen_g 3y agoGood link posted by s0rce in another reply, the authors' research seems to indicate the global effect is quite small, which tracks with what we might expect - it's a really big problem localised in cities because so much of the area around us is paved, but on a global scale the surface area of paved urban areas is not huge as a percentage of the surface of the earth.
- uoaei 3y agoHotter air results from the hot concrete. Then the air has more capacity for holding water instead of precipitating it out as clouds or rain. This increases the likelihood of 100%RH conditions, in direct sunlight, on top of a huge thermal mass heated to way above body temps, making heat waves deadlier because evaporative cooling becomes moot at that humidity and you're essentially in desert conditions surrounded by hot rocks.
- jimnotgym 3y agoTLDR; YES
- emtel 3y agoAll electricity used in a city ends up as waste heat - AC is no different. If AC is using (as claimed in the article) 10% of a city's electricity, then it is responsible for 10% of the waste heat in that city. There could be a short term spike as the AC rejects interior heat from buildings to the outside, but that will be balanced out later as outside heat is absorbed by the cooler buildings, or as cool air leaks to the outside.
- pjerem 3y agoThe issue IS the short term span. Nobody is complaining about ACs making cities hotter in winter. The issues comes from the fact that AC rejects heat from buildings when it’s already hot outside. It renders the city unbreathable in summer.
- adammarples 3y agoThis sounds wrong, lots of electricity does useful work that doesn't turn into heat (moving an electric vehicle, making plastic items) or escapes as other waste (light, sound, etc)
- BytesAndGears 3y agoThose are actually all converted to heat eventually, just with more steps. Moving an electric vehicle causes motion, but that motion is absorbed by the air and ground via friction with both, aka heat. Light is just energy in a photon — when it hits a surface that absorbs it, it becomes heat. And it can be quite a lot actually! If you put your hand in front of a really bright flashlight, you’ll notice a warm feeling. If you turn off the flashlight, it goes away immediately, proving that is the light itself causing the heat. Approximately all of the energy we use as electricity is just changing something into heat with some useful work in between
- agumonkey 3y agoWhere's research on passive thermal management (materials acting as heat phasors kinda) ?
- pazimzadeh 3y agohttps://en.wikipedia.org/wiki/Windcatcher https://en.wikipedia.org/wiki/Windcatcher
- Arn_Thor 3y agoBy coincidence I was walking around Paris today in 30+ degree heat. It was only really bearable in the shade, which the city has a lot of thanks to a good amount of trees lining the sidewalks. It was quite pleasant until we passed a convenience store and the heat and humidity of that part of the street immediately rose to oppressive levels. This was because an air conditioner for the store was venting into the street. The effect is stark and incontrovertible. There is the heat being removed plus some heat from the compressor and fan. Everyone in public and private spaces will be better off if we reduce AC usage as much as possible in favor of other solutions
- mikhailfranco 3y agoIt's not (just) the a/c in the store, it also has huge refrigeration units. In Asia, 7-Eleven is famous for its chilled air, but also has the walls covered with refrigerators for cool drinks, and there may be freezers for meat, seafood and ice cream.
- 6502nerdface 3y agoIn Las Vegas they solve this by blowing cold air onto the sidewalk through an always-open door, thereby cooling passersby, and perhaps enticing a few to enter for a game of slots.
- alistairSH 3y agoThat doesn’t really solve the problem. They’re just dumping the waste heat on the back of the building where tourists aren’t walking. And producing more of that waste heat because they’re trying to condition a leakier building.
- SavageBeast 3y agoSo lets look at how the refrigeration cycle works here and make some conjectures. If I understand correctly, this kind of system removes heat from one side and moves that heat out the other side. An AC unit with a structure as a barrier is a machine that removes heat from the confined structure and vents it to the outside. So, with enough AC units removing heat from sealed structures and outputting it into the atmosphere, seems plausible that getting enough of them together would behave like a kind of heater. Now, how did the air inside these structures get warmed up in the first place? Under normal conditions, is the air inside the structures WARMER than the ambient air? Does the structure itself somehow more efficiently harness the suns energy to warm the structure more than the ambient outside air? If the same energy source is heating the ambient air and the air inside the structures - and it is - its the sun here, don't we have a constant amount of energy warming the area? Some of that energy warms outside, some of it warms inside, but the amount is constant. So how could a device that removes heat from structures to vent it outside be responsible for a warming of the outside air? Unless the AC itself added some extra heat energy in the process OR the structures somehow more efficiently turned solar energy into heat, how could moving heat around cause a temperature increase? For example - on a warm day in a little European village, everyone lights a gigantic fire and adds non-solar heat to their homes. The devices that remove the heat would then be adding new energy to constant solar energy heating the town. Ambient temperatures would likely rise. But did the AC cause the temperature increase? Didn't the AC unit just move heat from structure to ambient? The AC added no heat in this case.
- anticrymactic 3y ago> Now, how did the air inside these structures get warmed up in the first place? Under normal conditions, is the air inside the structures WARMER than the ambient air? Greenhouse effect + no wind. The infrared emitted by heated objects are reflected by the glass, heating the room even more
- coda_ 3y agoAs someone said in a another comment: "There is the heat being removed plus some heat from the compressor and fan."
- 3y ago
- thatwasunusual 3y agoIsn't this well known, and not limited to AC, based on the Urban heat island effect? https://en.wikipedia.org/wiki/Urban_heat_island https://en.wikipedia.org/wiki/Urban_heat_island
- lowbloodsugar 3y agoThe asphalt and concrete is doing far more than the AC. But the city would have to pay for that and the poor need roads, so not as useful for lefties to incite riots against the “rich”.
- bigbacaloa 3y ago[dead]
- crazygringo 3y agoQuestion: is there a huge difference based on whether units are placed in windows vs. on roofs? Obviously for a window unit or split where the compressor is on the building's wall -- those are going to heat the air in the street. Ground level units most of all. But a lot of buildings place all their compressors on the roofs. And since hot air rises, does that produce any noticeable effect at ground level?
- lucb1e 3y agoWould it help to have an IR-reflective dish below hot AC units, to reflect more of the heat they put out back into space?
- contravariant 3y agoMost of the heat is probably spreading by convecting hot air, not as thermal radiation. A good chimney seems like it should be more effective, though it fundamentally still can't stop the fact that you're converting quite a bit of electricity into heat.
- lucb1e 3y agoThere will be some loss, but the heat trapped in houses wasn't going anywhere anyway. By putting it outside the home, there is a more direct pathway for it to be leaving the city. Though I wouldn't know how to quantify this by any sort of approximation, I assume it's less than the heat added from inefficiencies yeah
- soultrees 3y agoI wonder if it means that during the daytime, the cities are hotter but at night, the average temperature is cooler than before? Since all the heat trapped indoors has been pushed out into the world.
- kkfx 3y agoHonestly? That's just bullshit to try pushing people against A/C. Cities are hotter than outside because: - they absorb more heat :: concrete, asphalt absorb much more than grass or trees and disperse far more slowly. Just go walking in a bush, measure temperature at 1.5 m from soil, do the same in grass covered area and the same over a road. You'll see and feel the difference; - in cities there are MANY ICE vehicles whose engine produce much heat, much more than any electrical motor; - in cities there is less air circulation than in the open nature due to the high and heat-absorbing buildings; - in many cities glass coated skyscraper works like any other glass keeping much of Sun IR radiation inside. These are the reason why cities are hotter. Another proof? They are ALSO hotter in winter, not just in summer. In winter you can count extra heat from badly insulated heated buildings, little cold pushed outside by the so far limited percentage of people heating with some heat pumps that have air on their exterior side, but look at the numbers and you'll see they are more hotter than mere heats spread outside by badly insulated heated buildings. People should learn two things: - cities WAS a necessity to evolve in the past, but with the '80 logistic revolution they lost one of their last reasons to exists, manufacturing became cheaper to do far from customers, so far from cities. With the remote work the last remaining reasons vanish as well. As a result dense cities and high rise buildings have NO REASONS TO EXISTS anymore. Try to keep them and sell them as green, good for the future etc is just a push toward intensive human farming to keep people dependent on service they don't own, living to operate them so they can pay them. Since in the modern era cities can't be sustained the push needs to makes people accept bad living condition as a new normal; - we need to switch from a high density model, too dense for today state of tech and society, climate etc to a new less dense one, that's hard and that's means MANY will be simply "overflowing humans" to be put somewhere, since no one like that role, if told in such a crude way, some try to advertise such role with various "bells and whistles" but that's simply BULLSHIT. If you try reasoning about the above you'll understand a thing: such move to put aside a significant percentage of humans can't really work, never worked in history. It does work if the set aside cohort is very limited, the poorest, very isolated and very dependent, but at modern scale can't work.
- crooked-v 3y ago> we need to switch from a high density model, too dense for today state of tech and society, climate etc The populations of dense cities use fewer resources than the same population spread out in low-density settlements, especially when those cities are laid out to be properly walkable. It's just basic economy of scale. > in cities there are MANY ICE vehicles whose engine produce much heat, much more than any electrical motor; In cities, not having a vehicle is an option. Outside of them, it's basically required in most places.
- aaomidi 3y agoCity wide geothermal cooling pls thanks You can use huge water mains to transfer the heat
- Etrnl_President 3y agoCities are made of houses. Houses are made of rooms. If rooms are hot, aren't cities hot? If room heat is pumped outside, did the city temperature really change? What is the heat-island effect?
- a_square_peg 3y agoI really hope people don't take this result at its face value - the model used and the approach is extremely simplistic, which is essentially a pseudo 2-D simplification of urban canyon geometry, a street with buildings on either sides. I worked with the referenced model as part of my master's thesis. The bulk of urban heat island effect is driven by the radiative absorption of non-porous materials of the built-environment. Other heat waste put into the area accounts for less than something like 5% of the additional heat added when compared to rural areas.
- tasogare 3y ago> the model used and the approach is extremely simplistic Seems like a constant in doomsday "science": making a model that bear ressemblance to reality as much as SimCity does, run it to get the expected conclusion, then extrapolate and conclude with newsworthy title that X or Y is true in reality.
- thfuran 3y ago>then extrapolate and conclude with newsworthy title that X or Y is true in reality. It's worth noting that this portion is generally done by science reporters rather than the scientists. It's quite often the case that alarmist articles refer to research with much more measured and less sweeping claims.
- ChainOfFools 3y agoextremely relevant https://phdcomics.com/comics/archive.php?comicid=1174 https://phdcomics.com/comics/archive.php?comicid=1174
- blackbear_ 3y agoSimplification and abstraction are, in fact, basic tenets of all scientific and philosophical disciplines. https://plato.stanford.edu/entries/simplicity/ https://plato.stanford.edu/entries/simplicity/ https://iep.utm.edu/simplici/ https://iep.utm.edu/simplici/ Of course, you are more than welcome to voice concrete concerns about this specific study, if you have any (beyond what the GP already said).
- Aeolun 3y agoKinda weird. Of course air conditioning makes cities hotter, but the point is kinda to cool down the insides of the house, not the outsides. Small enclosed areas are a lot easier to cool. Heating up the 40 square kilometers of city outside by 2.4 degrees reduces 1 sqkm of inside temperature from a sweltering 30 to 23 degrees (note, made up numbers).
- AlDante2 3y agoBasic physics says yes.
- alexfromapex 3y agoYes, it’s very simple and undeniable. Instead of AC systems dumping heat into the air outside, they should be dumping it underground or to a hot water heater or something.
- p0w3n3d 3y agoJust plant trees in the cities. Go and Chech what is the difference of temperature in cities with trees and without. Of course sometimes it's too late: in my hometown they cut away 40 huge trees and made a market square, "because that's what they do in Netherlands" (exact explanation of local ministry), and now you cannot pass the market square in a hot day. Installation of some sort of irrigators doesn't make difference and is not hygienic (see Legionella). They took away trees and grass and made everything concrete. Meanwhile my parent's home is much cooler, no AC needed because they have trees between the blocks
- gandalfian 3y agoI wonder more about heating than cooling. Luddite paranoia perhaps but hot air rises up into space and away. Cold air sinks, where does it go? Outside air is a big heat sink but if entire urban areasn start pumping out MW of cold air in the future will the bottom of hills turn into ice rinks?
- amai 3y agoDoes a refrigerator heat up your kitchen?
- mensetmanusman 3y agoYes. The answer to the problem is a large increase in surface area of passive cooling technologies to reject sun energy during the day and to cool the surfaces at night through the atmospheric window.
- stuaxo 3y agoWhy not, they use energy.
- wortelefant 3y agoThe french get their energy from co2-free, cheap nuclear energy, the claim that more fuel is burned is only fractionally true.