That's not true. You've got a requirement to reduce entropy but none to pack it back into energy dense fuel.
C'mon, this is laughable. What are we going to do with it? Fill-up massive balloons? Also, I have never suggested that the objective should be to pack it back into energy dense fuel.
You are trying to talk your way around violating the laws of physics. Look, it's OK if you want to believe this. However, this does not change reality. This is why every single so-called solution has failed and ultimately is discredited.
As I suggested to someone else. If you don't see the point, do this:
Go to the store and buy a 10 Kg bag of finely ground flour.
Walk around your office or home and start throwing flour everywhere. Coat every single surface and crevice with it. Make sure it goes into your TV, computer, air conditioning system, setup a few fans to blow it around.
Now go back and retrieve every single particle.
The time, energy and resources required is astronomical when compared to the damage you can cause in 30 to 60 minutes. Anyone with minimal critical thinking capacity can understand that it will take weeks, if not months, of a very serious effort and lots more energy to remove every grain of flour.
Note that there is no requirement to put it back into the bag. You can eat it, cook with it. I don't care. Yet, you must repair the damage you caused down to the last particle.
Are you suggesting you can clean the room/office using less time, resources and energy than that required to create the disaster? I hope not.
That's the problem.
You need to understand that small-scale hypothetical first.
Now expand it to a planetary scale, where you have CO2 floating around the atmosphere at all levels, over every continent and ocean. The mere suggestion that we can actually claw this back should be ridiculous to anyone who stops to really apply some thinking to this problem. It's a fantasy.
There are significant and relevant differences between carbon dioxide and flour for this purpose; for example, carbon dioxide is a gas and therefore diffuses continuously through the atmosphere, so a scrubber in a fixed location can eventually remove all of it, which is common practice in submarines and space stations. Also, the amount of energy obtained by burning carbon is orders of magnitude larger than, and actually the opposite sign from, the amount of energy obtained by scattering a similar mass of solid particles around, and this is relevant because you are specifically and explicitly comparing the energy consumed by the emission and capture processes.
I have presented detailed calculations in the past only to be met with the same mindless brutalization via downvotes, comments and flagging. The HN masses are just as intellectually lazy as masses can be in any other context.
This is no different from recent events in the political spectrum, such as nearly the entire political and media machinery telling the world that Biden was just fine (and a bunch of other lies). Only those of us who managed to think outside the indoctrination seemed to have understood --years ago-- the sad reality that the poor man was being used and abused by the political machinery. Only when reality became inescapable did they start speaking the truth. In fact, it was worse than that, they actively attacked the man and popped him out of the system like a painful puss-filled pimple. The end result? They gave the leadership position to a candidate so flawed that billions of dollars and massive amounts of support from luminaries could not get her elected.
The point is: The truth always has a way to come out, sooner or later. Sometimes with undesirable consequences.
Climate change became a religion a long time ago. The domain is supported by the indoctrinated masses who love to regurgitate what they are told to think. Researchers fear going against the grain because their funding and careers depend on it. The powerful and those making money with this madness actively promote it and make sure they have support for insane projects. Frankly, it would be far easier to join them, regurgitate the nonsense and make millions of dollars per year by being a member of this dishonest club. Not my style. Sorry.
Regarding the flour analogy. You are reading too much into it. This was not a model of the planet and our atmospheric system. I only use these kinds of analogies to show how it takes far more effort, resources and energy to reverse damage that can be done in mere minutes. That's all.
Lot's of commenters on HN do not seem able to (or willing to) exercise critical thinking. Some might not have the requisite scientific background or real-world experience to understand what are otherwise simple arguments rooted in physics. One of the common comments goes something like: If we polluted it in X years we can clean it up in X years or less.
Of course, this is ridiculous. The example of flour spread all over the office is simple enough to illustrate just how silly this idea actually is. And, if someone cares enough to think it through a bit deeper, it also illustrates just how much more energy and resources is required than a sack of flour.
That's it. It isn't a model of a planet and its atmosphere. It's there to say: You cannot fix a problem with less energy, resources or time than what went into creating it in the first place. Nothing else.
> a scrubber in a fixed location can eventually remove all of it
That would be nice if it were possible. Sorry, this is another fantasy. Once again, things fail in a violent manner once considered at a global scale. You cannot filter air at a planetary scale, this is simply preposterous starting with the reality of building these kinds of systems every 10, 20, 50 or 100 miles throughout the planet, the scale, energy, resources and realities of air processing all work against you. These systems are far more likely to "filter" the same air over and over again than to actually "remove all of it".
In a prior life I was involved in large systems installations requiring the construction of clean rooms of varying scales, from small 20 x 20 foot labs to massive aerospace-level clean rooms (think Home Depot scale).
What works well in a smallish environment (a room, submarine, space station) quickly fails at larger scales. In the end, you cannot create a clean room by filtering the enclosed volume. That's not how it is done except for very specific applications (spacecraft, submarine, space station and that's it). The only way is to inject clean air and create positive pressure such that nothing is able to come in from the outside. Scrubber systems in the corner-case applications where this isn't an option are incredibly expensive and complex. They do not scale well at all.
Of course this isn't to suggest that we can bring in clean air into our atmosphere. My point is that the idea of filtering our entire atmosphere (or a substantial enough portion of it) only works on paper, research grant applications and proposals for funding by politicians eager to continue the narrative that drives unthinking masses to vote for them. Who wants to vote for someone who says "The emperor has no clothes"? Nobody. Far easier for the machinery to convince everyone that the naked man in front of them is wearing the finest garments every conceived. Sadly, that book [0] covers climate change with great accuracy.
Look, the scenario today is no different from what it has been for the last, 50 years or more. This articles [1] is an interesting compilation of predictions over time. All crazy nonsense. Yet, at the time, taken seriously and used to set policy and more.
Who would dare go against the likes of Nobel Prize winners, Ted Turner, Al Gore and other merchants of FUD? From a career standpoint, as academics, media or politicians, it would have been suicidal. Anyone can understand this. And yet, all of these and many others were selling pure unrefined bullshit. I mean, crap like this, quoting:
"A senior UN environmental official (Noel Brown) says entire nations could be wiped off the face of the Earth by rising sea levels if the global warming trend is not reversed by the year 2000."
(1970) "Air pollution may obliterate the sun and cause a new ice age in the first third of the next century if population continues to grow and earth’s resources are consumed at the present rate…"
"Harvard biologist and Nobel Prize winner George Wald, speaking at the University of Rhode Island in November 1970: “Civilization will end within 15 or 30 years unless immediate action is taken against problems facing mankind.”"
"In April 2008, media mogul Ted Turner provided far more detail than either Gore or Pachauri, emphasizing the consequences of climate inaction. “Not doing it will be catastrophic. We’ll be eight degrees hotter in ten, not 10 but 30 or 40 years and basically none of the crops will grow. Most of the people will have died and the rest of us will be cannibals. Civilization will have broken down. The few people left will be living in a failed state like Somalia or Sudan, and living conditions will be intolerable. The droughts will be so bad there’ll be no more corn growing.”
(2019, AOC) "The world is gonna end in 12 years if we don’t address climate change"
When I say that this domain has become a sad joke, a religion, an incredible farce supported by those seeking political and financial gain, rather than real science, well, there's ample evidence to support this statement going back over 50 years. In other words, it is far more likely that this is all a big smelly pile of bullshit than otherwise.
[0] https://en.wikipedia.org/wiki/The_Emperor%27s_New_Clothes
[1] https://www.agweb.com/opinion/doomsday-addiction-celebrating...
Sure, that's true, but are those the people whose opinion you care about? If you tailor your argument for them and leave out all the reasoning, you'll look like one of them, and people who are able and willing to exercise critical thinking on the topic will write you off. Don't tempt people to confuse you with dumbfucks like Ted Turner and Noel J. Brown.
> You cannot filter air at a planetary scale, ... These systems are far more likely to "filter" the same air over and over again than to actually "remove all of it".
You might be right that you need more than a single giant inverse volcano sucking carbon dioxide out of all of the air.
The diffusivity of CO₂ in air is 16mm²/s, or 1.6 × 10⁻⁵ m/s in SI units. Suppose, conservatively, that there are no jet streams or any other wind, so you have to rely entirely on diffusion, and that you've reduced the CO₂ around your scrubber to the pre-industrial 280ppm (0.012mol/m³), while the opposite side of the planet, 20000km away, is still at 400ppm (0.017mol/m³). If the concentration gradient were constant, it would be 0.25 nmol/m³/m over that distance. Using the given value of the diffusivity, this results in 4 × 10⁻¹⁵ moles per second per square meter flowing over that gradient. The atmosphere is in effect about 8 km tall, so at the halfway point of this flow, the great circle halfway along the path, you have 320000 km² of cross-sectional area, through which your flow is about 0.000128 mol/s. If you're trying to clean up the air over, say, 20 years, that works out to about 800 kilomoles, only about 36 tonnes of CO₂.
But we had to remove 2.3 gigatonnes of the atmosphere's 7.8 gigatonnes of CO₂, not 36 tonnes. We need a system that's 64 million times more powerful, which means that instead of being 20000 km away from the farthest points on the planet, it needs to be about 20000/8000 = 2.5 km. (Also, the above is assuming that the gradient remains constant, which of course it can't; you'll have a much stronger cross-sectional gradient around anything like a point sink or source of carbon, because the same mass flow is spread over a much smaller area. I don't know the exact solution for diffusion on the surface of a globe, but I'm confident the above is in the ballpark.)
But we do have wind; to take the most extreme example, the jet streams travel about 50m/s, so any parcel of air in them circles the globe about once a week. So if you set up your antivolcano near a jet stream and create a locally very low CO₂ concentration, CO₂ will diffuse rapidly out of the jet stream as it travels through your area and diffuse rapidly back into the jet stream on the other side of the planet three days later.
So if you have winds that bring all of the atmosphere within 2.5km of your antivolcano at some point within those 20 years, you can scrub it all. All of it.
https://www.usgs.gov/news/volcano-watch-global-reach-volcani... says of Mount Pinatubo:
> Notable eruptions in recent years appear to have affected climate. One example is the 1991 eruption of Mount Pinatubo in the Philippines, which injected nearly 20 million tons of SO2 into the stratosphere that became dispersed around the globe in about 3 weeks. The recorded effect was a 0.5 degrees C (0.9 degrees F) drop in temperature for the following two years.
So in practice the timescale on which an antivolcano's CO₂-scrubbing effect would reach the air on the other side of the planet is only a few weeks, not the hundreds of millions of years that the naïve diffusion calculation suggests.
You say:
> In the end, you cannot create a clean room by filtering the enclosed volume.
I haven't tried, but I'd venture to guess that that's because dust, like flour, doesn't diffuse through air (at human temperatures on human timescales). It's a thousand times denser than air, so it can settle on surfaces and get trapped in certain kinds of airflow patterns. Carbon dioxide doesn't behave like that. It behaves like water vapor.
> Scrubber systems in the corner-case applications where this isn't an option are incredibly expensive and complex. They do not scale well at all.
Unlike cleanroom filters, scrubbers, which are gas-exchange devices used for removing unwanted gases from air, are actually very cheap and simple, and they scale extremely well; they are already being operated at many-megawatt industrial scale, which is how we ended the acid rain problem caused by coal power plants. A CO₂ scrubber can be as simple and low-tech as a wall painted with whitewash, though soda-lime scrubbers (a few percent of lye added to the whitewash, which is balled up in little beads to let the air pass through) are much more common because they are so much more compact. They are in wide use for general anesthesia, scuba diving, and decompression chambers. On the order of a million recreational scuba divers own their own scrubbers. You can buy a bottle of 5 liters of soda lime for €32 at https://www.diveavenue.com/en/high-pressure/1860-chaux-spher...; if you stick a porous breathing tube into the bottle, it becomes a scrubber, although you'd probably die if you tried diving with it.
Other kinds of gas scrubbers are available as disposable cartridges from 3M for their respirator masks, so it's absolutely not true that they're "incredibly expensive and complex", but let's stay focused on CO₂ scrubbers here, since that's what's relevant to climate change.
The disadvantage of lime CO₂ scrubbers is that, although they are very simple, regenerating the lime requires heating it up to 900°. People have been doing this for 12000 years (it's probably literally the oldest human chemical process) but it takes a lot of energy compared to other sorbents like triethanolamine, which is why amine scrubbing is currently the mainstay of both submarine CO₂ scrubbers and point-source CO₂ capture pilot projects. There's a nice process flow diagram of a submarine CO₂ scrubber at https://sites.psu.edu/mooneypassionblog2/2022/03/22/how-subm....
As for scaling, lime burning, in the slightly altered form of portland cement making, is one of the world's largest-scale industrial processes, producing 4 billion tonnes of cement per year and emitting 1 billion tonnes of CO₂, which you'll notice is about 2½ years for the mass of the carbon dioxide we have to remove. (Portland cement, unlike Neolithic-style lime cement, only reabsorbs a fraction of that CO₂ when it sets.) So we already know we can scale lime kilns up to the requisite levels; we just have to capture their carbon dioxide output. There are also a bunch of startups trying to scale up amine scrubbing and other processes to direct air capture, but I'm skeptical that their supply chains will be able to compete for scale with the world limestone-and-other-calcareous-stone industry.
> My point is that the idea of filtering our entire atmosphere (or a substantial enough portion of it) only works on paper, research grant applications and proposals for funding by politicians eager to continue the narrative that drives unthinking masses to vote for them.
Every engineering idea only works on paper until you build it. That's how engineering works: you make things work on paper, you validate your assumptions with prototypes, you learn from your mistakes, and finally you create something that never existed before. Your criticism here is a fully general criticism of every technical innovation in history; it doesn't distinguish between perpetual motion machines (which work on paper if you screw up your calculations badly enough) and any routine civil engineering project such as a bridge embankment.
This also means that the world cement industry is not currently large enough to carry out the necessary direct air capture over a timespan of decades. You need a carbon dioxide capture industry 10 or 20 times larger; at current energy and material prices, this would cost on the order of 6 trillion dollars per year, about 6% of the world GDP of US$105 trillion per year, nominal, World Bank estimate: https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nomi.... World GDP has been growing about 3.9% per year, so rather than setting us back to the Stone Age, or even to the 18th century, this staggering expense would set us back to about the time Silicon Valley Bank collapsed, Hamas invaded Israel, OpenAI released GPT-4, and Microsoft bought Activision Blizzard.
This clearly demonstrates that it is technically feasible already, just not economically/politically. Rapidly falling energy prices thanks to the transition to super-cheap renewable energy will ease the economic difficulties, though the project may still require international diplomacy.
Also, https://earthscience.stackexchange.com/questions/994/how-lon... says, "The time scale of interhemispheric tropospheric transport is in the order of one year," not a few weeks. I assume that the difference from the Mount Pinatubo number is because the troposphere mixes more slowly than the stratosphere because in general the winds in the troposphere are slower. (However, the jet stream in particular is at the tropopause, where the two meet.)
We understand it well enough to know that it does not apply. Flour in crevices is not a gas in a mix of gasses
Your problem is you must pick the right small-scale hypothetical.
For gasses, any single removing device operating faster than the input devices will eventually remove ALL of the target gas. Yes, the rate gets asymptotic, and yes, more devices are better than one, but every molecule will all by itself come out of every crevice, and eventually bump into the removal device. That will NEVER happen with your flour example.
This principle is already used for pretty much every air cleaning device in use both on the planet and in space.