There is no valid argument for CO2 removal. No matter how you slice it, emissions reductions are more cost effective than removal. If we wreck our economy in the process of trying to prevent global warning then the net effects will be even worse.
However, there are still two very solid arguments for capture, even if it has greater costs.
First, even if we somehow make emissions go to zero next Monday and forever after, the CO2 already baked into the atmosphere will still cause massive warming for centuries, and this will cause massive ecological disuption. Only removing the carbon (and/or implementing sun-blocking technologies) will allow a fast enough reset to pre-industrial levels and avoid such damage.
Second, it is extremely unlikely that we could make emissions go to zero in anything like the required timeframe. Even if somehow 100% of the people and politicians became convinced and decided to start next Monday, it would be decades before we approached zero emissions. Replacing all the fossil-fuel technology will not be instant. Thus, again, capture and sun-blocking tech has a definite role in rapidly repairing the damage.
What about politically effective? You can start removing CO2 from the air without coordinating your effort with all the industrial powers of the world.
This is an invalid argument, in a world where China and the US are quickly becoming sworn enemies unlikely to agree on anything?
Human activiy (the extraction and burning of fossil fuels) puts some 11 billion tonnes of CO2 into the atmosphere every year.
There's a lot of industrial activity required to move 11 billion tonne (and that in itself creates additional emission issues to circimvent).
At this point in time the largest global project to sequester CO2 is adjacent to a SANTOS natural gas extraction project.
* It's not yet working as planned.
* Were it to work as planned the total CO2 sequestered would be a tiny portion of the amount required to be removed.
* It's a "cheat" obfuscated by mirrors in any case - the CO2 planned to be sequestered is a small proportion of the CO2 released by the natural gas extraction project its part of.
But, as I explained in https://news.ycombinator.com/item?id=42423291, the price of renewable energy (in particular solar photovoltaic) is in free fall, which is suddenly making vast amounts of very cheap energy available. The biggest cost of even existing direct-air-capture technologies is energy, so cheaper energy makes them viable in cases where they weren't viable before. Probably those prices will continue to fall further.
In short, we shouldn't be surprised that carbon capture hasn't taken off yet; we're still on the fossil side of the renewable energy transition.
The great unspoken catch to direct air capture technology as that develops is while it will (at sufficient scale) mitigate the extraction of "old" carbon from traditional fossil fuel deep earth operations it will likely serve to maintain the cycle of already extracted carbon in the air: (energy + air) -> fuel -> (carbon in air).
Don't get me wrong, these are good steps forward, they're just not solutions unto themselves - we still as a species need to reduce the absolute amount of insulating material in the atmosphere.
Currently we are not.
When we do start to wind back the amount added, we have to keep winding it back by a few hundred billion tonne.
There are a variety of different possibilities as to what to do with the extracted carbon. CO₂ is kind of an inconvenient form for making fuels from, so as long as they can cook oil and gas out of shale, people might just pump the carbon dioxide down wells and let it serpentinize some olivine, rather than reducing the carbon back out of it.
https://www.iea.org/reports/co2-emissions-in-2023/executive-...
I haven't checked against the GeoPhys journals (I should, but ...), FWiW wikipedia has it that:
In October 2023 the average level of CO2 in Earth's atmosphere, adjusted for seasonal variation, was 422.17 parts per million by volume (ppm).
Each part per million of CO2 in the atmosphere represents approximately 2.13 gigatonnes of carbon, or 7.82 gigatonnes of CO2.
~ https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_at...
That's total, not just the excess portion added in by human activity and sourced from the bowels of the earth via mining for concentrated old sunlight energy.
Still, despite the fractional ppm composition that's a full atmospheric total of 3,301 billion tonne.
Here in W.Australia we move approx one billion tonne of iron ore from the Pilbara to (mostly) China per year. That takes some effort and energy.
A simple calculation in units(1) shows that your figure is the right order of magnitude:
You have: 400ppm 4pi earthradius**2 atm / gravity
You want: trillion tonnes
* 2.1080571
/ 0.47437046
You have: 422ppm (carbon + 2 oxygen) 4pi earthradius**2 atm / gravity (21% 2 oxygen + 79% 2 nitrogen)
You want: trillion tonnes
* 3.3925982
/ 0.29475934
Absolutely hilarious. Let's compare notes in twenty years. You are too vested in the cult to be able to accept and comprehend reality.
It would also do everyone a service if you withdrew your claims that turned out to be wrong, as I did in the comment above and in https://news.ycombinator.com/item?id=42440198. That way they don't have to wade through the intricate details of the argument to figure out which of your claims still stand.
In the end the question is: are you here to figure out what is true? Or are you here to conceal what is true, like Ted Turner? I assumed the former, based on past experience, and asked dang to unflag your original comment as a result, even though it was a bit ranty. But this "hilarious" comment makes me wonder if I was wrong.
We're definitely not at that point, or anywhere near it, but it exists.