Yeah, there's a timing issue with tree planting certainly. You have to discount the trees some amount for the effect. And it's not a 100 years. That flight will be covered by the oak in under 20 years.

Of course, you still have to discount but it makes things much more feasible.

That's why you usually don't plant trees. You can do other stuff that wouldn't otherwise get done.

A tree that only lasts 20 years will probably return all of its stored carbon to the atmosphere by burning or rotting. Only the old forests (100 years) retain it long enough to make it an effective carbon sink.

The tree will last longer than 20 years, but it'll have achieved parity by that time.