So 1.5% of the worlds GDP to break even on carbon emissions in our current state. About 2.5% to turn the clock backwards and bring us back to pre-industrial-revolution levels by 2100.

Not great, but not completely outside of the possible. Provided sufficient political will.

Course this current system and pricing doesn't work via direct-air capture, so we're only looking at breaking even with it, not turning back the clock.