And lots of land. Suppose you can plant them in say 4m rows with 4m separation, it would be approx 60K trees per 1km2 or 20million km2 in total. Twice of the size of the US?
I guess some land may become available as permafrost melts?
Ah, so we've been trying to do good all this time with industrialisation!
That is a lot of trees, but a decade’s worth is a lot of emissions
Also when they are grown (30 years?) you could chop them, stack the wood or use it in some way that doesn't release the carbon and then grow another lot.
Indeed, we don't talk about the absolute numbers a lot but reportedly more than half of all CO2 emitted by human industrial activity has been released since 1988. So our current per-decade pace of emissions is truly colossal, historic, unprecedented, pick your term.