I think many of us just haven't internalized the percentages of gasses, and probably, like myself, often have it all backwards. An alien doing a fly-through of our solar system would describe our planet as a nitrogen atmosphere.
In descending order:
Nitrogen: 78 percent
Oxygen: 21 percent
Argon: .9 percent
CO2: a measly 0.04 percent
The NOAA has a station on Mauna Loa in Hawaii. It has been continuously collecting CO2 data since 1958 and CO2 has gone from just over 300ppm to the current 414ppm.
It should also be noted that the total atmosphere (dry + water) is about 3% water vapor by weight and H2O makes up the majority of the greenhouse effect.
CO2 isn't a problem because it's the biggest greenhouse gas, it's a problem because it's the one (the biggest anthroprogenic one) pushing us over the equilibrium where net warming is zero.
This is actually an incredibly important point, because higher temperatures mean more water vapor in the atmosphere. However, that also means more clouds, which counteracts warming to some degree.
The impact of clouds on climate change is one of the biggest difficulties in modeling climate change. The IPCC report goes into it a bit. My understanding is that computationally it's a bit like predicting the weather into the future - a lot of uncertainty due to the chaotic nature of the system.
For a long-term climate model, it might work to average out (over space and time) some critical phenomema and assume a steady function from e.g. average air temperature to ice cap size and cloud cover.
(source: wrote some homework-grade numerical simulations, physics major.)
The low concentration means CCS will be slow. However, we can’t drop CO2 to pre-industrial levels in a week, that would probably cause significant climate instability. The logical thing to do would be to drop the levels at around the same rate as we have increased them. That may be too slow to prevent significant climate change in the meantime. Perhaps the rate could be adapted to how bad things seem.
Carbon is not 4% of the air, it's 0.04%, a thousand times less concentrated again. To get "1 litre of carbon solid"[1] out means sucking in and paying the cost of processing 2,500,000 litres of air.
[1] as if that means anything sensible here, lol.
But things are sounding really bad and carbon capture technologies may be necessary once ordinary methods of reducing carbon production are exhausted.
But geeks getting excited about carbon capture now reminds me of a guy eating a burger and saying "sure, the cholesterol is bad but I can just get heart bypass".
In this situation you suddenly realize that cholesterol is bad. Remember, you've been doing this feeding for quite a while and, while knowing about cholesterol, weren't that concerned - things didn't notably change for you. Now you start feeling some inconveniences and decide to do something about the cholesterol, as doctors recommended. Now you still have to eat regularly, and can't stop the conveyor, and can change what's on the conveyor only rather slowly - so what would you do?
Among other things you'd probably think "sure, the cholesterol is bad but if things would go too bad I can at least get a heart bypass". I think it's a usable model of the current situation.
That problem is that human civilization is becoming less rational in response to the stresses of the situation.
The degree to which a country or the entire world has ever able to act "selflessly" or broadly altruistically has always been limited but some things have happened - banning Ozone destroying chemicals was an action. Wars have shown change (negative change but change) can happen quickly if a society needs it. I don't think there's a fundamental technological barrier to forcing a lessening of green house gas production. Rather, it's a loss of capital investment barrier. The forces arrayed to prevent oil assets from losing value are huge. Maybe a fund could just buy these assets and let them wind-down or maybe we're all doomed or maybe there's another escape.
I'm not sure but I think pushing for quick, not slow action, is appropriate, whatever one think is realist (the end of the human race looks realistic, certainly but I don't see a reason to simply accept it).
60 Euros per ton doesn't seem terribly bad. Burning a gallon of gas generates about 20 pounds of CO2 (hydrogen from the gas bonds with oxygen from the air, resulting in CO2 emissions that weight about 3 times as much as the weight of the original gasoline). So, every time you refill a 15 gallon gas tank, that's about 300 pounds of CO2. I'm not sure if the chart uses metric tons (about 2200 pounds, let's say it does.
It looks like most of the CCS options on that chart are in the range of about 40 to 60 euros per ton. 60 euros * (300 pounds / 2200 pounds) is about 8.18 euros, or about 9 US dollars. That's significant; people would complain. It's not insurmountable though. People would still keep driving.
It's worth noting that the carbon capture options listed are specifically carbon capture from existing fossil fuel power plants. There may well be other carbon capture options that are cheaper, like sequestering carbon from plant biomass. (I didn't read the paper, maybe it goes into that.)
The problem is that we can't pass an arbitrary policy and expect it to be dutifully followed from day one. So, economists would put a cost on a policy - say, how much money would some oil user require so he'd stop polluting? Remember if you just order him to stop, he can vote you out of policymaking. Or he may happen to live in a jurisdiction where your order turns into something more optional.
Taking that into account, I think CCS considerations make a lot of sense.
But I'll be dead so whatever. Live your best life.