Thank you for doing these calculations! 0.39% of anthropogenic global warming is surprisingly large, but it doesn't sound like a big impact to me. I mean, it sounds like about the same greenhouse effect impact as the San Bernardino metropolitan area (5 million people) or the Chongqing metropolitan area (12 million people).
Retric: I regret not having responded in time to your comments, which I agree with.
> Unless we manage to make massive cost reductions for atmospheric CO2 sequestration,
We will. The main reason atmospheric carbon capture is expensive is that it requires a lot of energy, and the cost of energy is falling through the floor because of cheap renewables. Expensive high-efficiency chemistries for carbon capture will cede to simpler, energy-hungrier chemistries, the ultimate reductio ad absurdum being something like soda lime. Soon enough synfuel from atmospheric carbon capture will be an attractive alternative to fossil fuels for transport (within 15 years), and then it's just a question of capturing the combustion products from the fuel. We may need to start adding high-multiple GHGs to the atmosphere to compensate for carbon dioxide we remove to make plastic. Hopefully shorter-half-life GHGs than sulfur hexafluoride, though.
The US has taken a very aggressive policy stance against renewables and in favor of fossil fuels, but ultimately it can't prevent the inevitable. If it continues to punish the importation of renewable energy equipment, US subjects will import cheap synfuel, or, failing that, they'll import electrolytic iron, zinc, or magnesium to use as fuel, from countries like Chile, China, and Dubai.
I am bullish on the rapid global uptake of low carbon electrical generation (global solar PV deployment alone is almost at 1 TW/year), but bearish on carbon sequestration being viable unless sucking the CO2 out of the ocean (due to energy required via atmospheric capture). It’s not just energy required, but how much carrier (whether that’s air or water) you need to process per unit of CO2 removed.
Stanford Study: Renewable Energy Beats Carbon Capture on Cost and Climate Impact - https://carbonherald.com/stanford-study-renewable-energy-bea... - June 11th, 2025
Energy, Health, and Climate Costs of Carbon-Capture and Direct-Air-Capture versus 100%-Wind-Water-Solar Climate Policies in 149 Countries - https://pubs.acs.org/doi/10.1021/acs.est.4c10686 | https://doi.org/10.1021/acs.est.4c10686
Climeworks’ capture fails to cover its own emissions - https://heimildin.is/grein/24581/ - May 15th, 2025
I'm skeptical of the Heimildin article, because it contains obvious factual errors:
> equivalent to almost four times Iceland's electricity production, which is about 20 terawatts per year.
You can't measure electricity production in terawatts per year; you can measure things like solar panel deployment speed in those units, as you correctly did. This makes me wonder how many other factual errors I failed to spot in the article.
But, yes, we should not expect atmospheric carbon capture to be economically feasible yet, and when it is, we should expect most companies that attempt it to fail, just as most solar panel companies have failed. But remember that solar energy is free when the sun is up; there's no economic benefit to curtailing your electric production because your batteries are full. So we should expect vastly more energy-intensive approaches than Climeworks' to be viable.
Atmospheric carbon capture isn't an alternative to renewable energy. It's what you do in response to the much lower energy costs resulting from renewable energy, and to reverse the damage already done.
> Expensive high-efficiency chemistries for carbon capture will cede to simpler, energy-hungrier chemistries, the ultimate reductio ad absurdum being something like soda lime
I haven't looked into the topic much at all but that does resonate. It reminds of the way solar farms are becoming less fine-tuned (e.g., no sun-tracking tilt motors anymore) as panel costs drops through the floor.
In terms of impact, it doesn't sound major, I agree. But it's still work that will need to be done. As industry and transport become more electrified, and electric generation gets decarbonized, impacts like high-multiple GHG gases will become a bigger and bigger share of CO2e still happening.
Atmospheric CO2 is already too high to avert terrible long-term impacts of global climate change. Unless we manage to make massive cost reductions for atmospheric CO2 sequestration, weaning entirely off of fossil fuels will not be sufficient to avoid climate change impacts if we still add long-lived GHG molecules to the atmosphere. (SF6 has an atmospheric lifetime on the order of 1000s of years.)
Think of it like the tide going out in a rocky bay. As the water level recedes, rock pillars that used to be too deep underwater to worry about now are close enough to the surface to cause you trouble. On the other side of the same coin, putting in the work to clear them helps give you as big a space to operate in as you had before.