[angusb]

this isn't quite right - if you use zero carbon sources (e.g. solar) to power carbon removal the operation would be net carbon negative.

"but why wouldn't you just use that solar capacity to displace coal plants on the electricity grid??????"

there's already a rapid switch of installed electrical capacity from fossil fuels to solar/wind, but electricity typically accounts for 20% of a developed economy's emissions, so after that we need to look to decarbonise other parts of the economy.

removing carbon from the wider economy involves some low hanging fruits (e.g. better insulation in houses) followed by a succession of increasingly difficult and expensive removal processes, with a very long tail.

at the far end you have things like removing carbon emissions from long haul flights, which is extremely difficult - once it gets this hard, it's much more practical to use solar to power carbon removal.

we can't wait for emissions to go to zero before investing in carbon capture because we'd be waiting decades for battery energy density to increase by orders of magnitude before they are good enough to support long haul flights. We don't have that long

[el_nahual]

Agreed on the need to invest in carbon capture now. My main argument was that a) reducing emissions to ~0 is going to be necessary even if we invent some insanely efficient carbon sequestration tech; b) the longer we wait, the worse the problem gets, in an exponential way. Emissions reproduce; c) Therefore the bulk of our effort should be spent trying to get emissions down to 0. Because if we fail at that (a task that we know how to accomplish), then no amount of sequestration tech will save us.

[angusb]

Hmm, still not sure I agree. Reducing emissions to close to 0 is definitely very important but it seems probable that we'll reach a steady state where some niche sources of carbon still persist, and are accompanied by corresponding capture. Some niche sources are just unbelievably hard to decarbonise

If in 20 years 1% of our emissions remain but they are accompanied by capture (with a multiplier to account for inefficiencies in capture) then that would be ok by me.

(You'd still want the extra carbon removal to reverse the warming caused by past emissions ofc)