The cost of global warming and the benefits we've reaped from its cause (cheap power) are both a significant fraction of world GDP. Planting 160 trees per person would be cheap, and even easily do-able by an individual in a few weekends (though it's obviously way more efficient to hire specialists to do it en mass).

The total suitable land area needed (more than the area of the USA, by my estimate) is much more likely to be the limiting factor than the per-person difficulty.