The other thing with trees is that they aren't permanent carbon sinks in the way that coal underground is.

Wood will eventually rot or burn and release it's carbon.

Human beings have taken carbon in the form of hydrocarbons underground and released is into the C02 - O2 cycle in the air. The main way to solve this would seem to be putting it back into the ground. So, reverse coal-mining? Turning wood into charcoal and burying? These seem like necessary counter-parts to simply growing trees.