In pursuit of comfort, the human race loves to heat and cool itself when it is not necessary. This has disastrous physiological and environmental impacts.
What is necessary?Let us define necessary heating and cooling to avoid any confusion. Heating and cooling can said to be necessary when our health relies upon it (e.g. not freezing to death).
So what is healthy? Heat stroke begins around a core temperature of 105 °F (40.6 °C) and fatality is expected at 107.6 °F (42 °C). 136 °F (57.8 °C) is apparently the highest recorded human core temperature. A spot in the Grim Reaper's ice cube tray is secured around a core temperature of 80.6 °F (27 °C). 56 °F (13.7 °C) is apparently the lowest recorded human core temperature.
Anyone who works indoors operates nowhere near these extremes. People who are working outdoors are not really consuming heating and cooling anything like those who work or live indoors. For that reason, the office worker and home-dweller will be our focus.
A back of the envelope calculation using the formula in this NASA report leads me to believe that just moving around a bit will allow one to tolerate a temperature as low as 45 °F (7 °C). Average air velocity of 787 ft/min, average skin temperature of 95 °F (35 °C), average man's surface area of 1.9 m^2 to match ~150 kcal/hr...try it out. I am willing to accept any heating around this region as necessary, even 10 degrees higher. Most office workers and home-dwellers are still not exposing themselves to that kind of cold.
The dry-bulb temperature limit for an non-heat-acclimated woman at rest in 90% humidity with some light air movement is 93.2 °F (34 °C). Anything above that and the core temperature will begin to rise.
Odds are a person's core temperature does not even begin to rise until a mean discomfort index (which is like a wet-bulb globe temperature, which basically means temperature taken to include not only heat itself but also the elements) of 89.6+ °F (32+ °C).
It is worth mentioning mean discomfort index and wet-bulb globe temperatures (WBGT) because the typical office drone is shielded from all of Nature's nasties. Yes, HVAC plays a role in that shielding, but being in a big, fat office building or comfy little cottage does a lot of the leg work.
OSHA itself has a whole packet on this topic, but the key piece from page 70 is that a common limit for light work appears to be 86 °F (30 °C). For moderate work the recommended limit appears to be 80 °F (26.7 °C). Light and moderate work means a work-rate of 100 to 200 and 201 to 305 kcal/hour, respectively. It is generous to attribute that sort of expenditure to folks in an office.
What are we doing to our bodies?If you have been in an air-conditioned office or in a home, it should be obvious to you that we operate nowhere near the extremes of temperature outlined here. My experience would say most people keep the thermostat in the low 70s at best, but better we look at references.
The American Society of Heating, Refrigerating, and Air-conditioning (ASHRAE) gives a pretty big comfort range of 67 °F to 82 °F (19.4 °C to 27.8 °C). This campus tightens that up a bit of actual operation, to a range of 68 °F to 78 °F.
It is probably hormetic for (most of) us to be exposed to a wide range of temperatures. The cold might be key to a healthy metabolism. Individuals who regularly bear the cold show increased amount of brown fat. Brown fat helps mammals keep warm and burn excess energy. There are some implications there for maintaining a healthy weight and a healthy body (section IX cuts to the chase, but brown fat is fascinating so at minimum take a look at IV, V, and VI). At a minimum, cold is capable of helping you burn off excess food energy. Mild cold exposure burns as much as ~23 calories per hour (27 W) and extreme cold burns as much as ~258 calories per hour (300 W).
Heat exposure, while not necessarily a metabolism booster, likely does confer some health benefits. Warming the body may be useful in the treatment of depression. There is also a long tradition of hydrotherapy and cold water swimming, showers, and so on, which is slowly making a comeback. The papers I could find were not very impressive, but if someone would like to dig deeper there are some cited here.
The pursuit of comfort without any hardship is a surefire way to deny yourself any growth as a human being. It also happens that the hardship is better for you physiologically as well as spiritually.
A grizzly bear wards off depression and makes use of its ample brown adipose tissue.
What are we doing to our planet?Globally, cooling alone accounts for 3% of all primary energy usage and 10% of global electricity. By 2050, it is expected that cooling will account for 16% of global electricity (and one can infer something like ~4 to 5% of all primary energy). Space heating meanwhile has to account for somewhere between 10 and 15% of global energy.
Worse, air conditioning drives peak demand upward. The peakier the demand, the greater the need for peaker plants, which primarily burn fossil fuels. Renewables are too few and too intermittent, storage is not yet widely deployed, and nuclear is out of favor in most developed countries.
Air-conditioning units also often leak refrigerant into the environment. These refrigerants are green house gases. In fact, they are arguably worse green house gases than CO2 for two reasons: they are often orders of magnitude more effect at trapping heat than CO2 and they are no free sinks for such gases in the Earth system (like trees).
Cooling specifically could be a positive feedback loop, where energy consumed for cooling generates waste heat and pollution which in turn has a warming effect which increases temperature extremes, which of course increases the energy consumed for cooling and so on. This is just a plausible thought, not a hard truth, but it does gesture toward a risk of exponential increase, doom, and gloom.
What are we going to do?Probably nothing.
This particular piece of propaganda demonstrates the way a lot of people think. We heat and cool spaces when we do not need to because we all worship at the altar of Mammon. Realistically, we need to tear it all down and start over to make any real change. Or we can continue to sacrifice life itself at the altar of Mammon.
I am not optimistic that the human race will stop worshiping Mammon any time soon, so for the reformists I instead offer the following sub-demons for sacrifice (though I am not optimistic about behavioral changes, either):What are current trends in the USA? Just what would such behavioral changes save us? We will take a look with EIA consumption data and dry bulb temperatures from NOAA from 1973 to 2018, moving in chunks of 5 years. We will be looking at consumption in terms of kilowatt-hours per person with an air conditioner on the residential side, and straight kwh on the commercial side. Heating and cooling coefficients are kWh (per person) per degF over or under a determined breakpoint. The breakpoint is determined by splitting the data at the point that provides the greatest weighted average standard deviation over kWh (per person).
In the residential sector, people are using less and less power. Baseline energy usage is down and seems to be trending further down, likely thanks to more efficient appliances. Weather-sensitive usage, which I am wagering is primarily cooling and heating related, has been stable over the last 20 years. From 1973 to 1995 or so, cooling sensitivity seems to have increased. My best guess is that the transition from window units to central air drove a lot of this. The rise might be due to the moral hazard of central air: it is quiet, easy to leave on, and leads one to cool their entire home because they can. The stabilization might be due to learning effects: over time, system design improved, technology improved, and duct-work became less leaky.
In the commercial sector, more and more power is being used. We see huge leaps in power consumption, with things steadying off some time in the 1999 to 2003 range. This pattern is visible in the weather-sensitive cooling load as well as the baseload. Big drivers I would guess at include urbanization (office buildings are actually obelisks erected specifically to sap the life force of the planet) and the advent of the information age. As for why things steady off, I expect that outsourcing of manufacturing plays a role, but I have no idea.
Things to note here:Maybe more efficient air conditioners will be developed. Maybe the energy we use will become greener. Still, is this behavior sustainable long term? Long long term? Maybe when we find a way to dump our waste heat outside the Earth system. Maybe when we find a way to recover the waste heat. Maybe when we find a way to engineer Earth's climate.
I would not deny anyone their techno-optimism. Please, work on some of these maybes. But even if you are confident these are all solvable problems, why make the problem worse and yourself weaker at the same time? Hold another possible future in your mind:
The growing and developing nations' collective demand for air conditioning booms. The demand for energy booms right along with it. Smog crawls across the gray sky like the breath of a trash dragon. Glass and steel ziggurats dot the hot, rotting landscape. Inside, the priests of Mammon sit in scarves, typing away.
Change your habits if you can. Preach the gospel of doom to the disciples of Mammon. Wake. Work. Weep. Sleep. Do it all again.
I'm more than happy to share data and code upon request (just don't bully me), or help you locate linked papers should you have any trouble. Shoot me an email.
P.S. While I dithered on publishing this sneeze, someone wrote something on this topic that is much better. This piece is fantastic. Give it a read.