Everything I've seen is the cost would be quite manageable. Sure, you're talking billions a year. But the figures I've seen are that it could be funded by something like a fraction of a penny per gallon of gasoline sales. It would require international cooperation, but it might be as simple as just adding an additive to jet fuel.

Termination shock is a legitimate fear. But again, the cost is relatively cheap. It's not something we can't continue to fund even if we have a major depression or a world war.

I couldn't justify rolling the dice on this if the stakes weren't so dire. But look at it. We're literally talking about the near-certainty of complete societal and ecological collapse from climate change. I'll trade "possible death" for "certain death." It's not the perfect solution, but we are well past the point of perfect solutions.

And moreover, it gives us what we really need: TIME. We have a path to a carbon-free future. But a planetary civilization is the slowest of ships to turn. We're trying to completely revamp the very material foundations of our entire lives. Solutions like atmospheric CO2 removal are not practical with today's technology. But, in principle, with sufficiently cheap power and good enough automation, meaningful direct air capture should be possible.

For example, by 2050 the world will be pretty awash in solar panels. Project the production curves forward, and we'll be sitting on a massive abundance of cheap available power. Especially in the summer time, we'll have access to vast amounts of otherwise wasted power. And if you had really good automation and robotics by then? Maybe then it becomes possible to affordably construct an industrial complex that would rival the current world's petrochemical complex...all just to take CO2 out of the air. Totally impractical now. But 2050? Or 2100?

Or, in the worst case, you don't need to sustain this forever. My understanding is that the main mechanism that governs the timing is ocean currents. It would take about a thousand years for ocean currents to move enough water up to the surface and back down to return atmospheric CO2 to pre-industrial levels, but we're talking a task on the order of centuries, not forever.