There are 7 billion people on the planet. Couldn't we just... have everyone plant a few trees? Trees weigh something like a quarter of a ton+ when fully grown, and pull directly from the atmosphere. Even if we remove the 50% of people who live in cities without yards, if every rural human planted 5 trees a year we'd end up sequestering a lot of that carbon, right? I know it's not permanent but if you just keep planting trees you can easily buy yourself 20 years with the open space we have.
Planting a tree won't do much on its own. It must survive and grow. The thing is, a lot of places where trees thrive are already covered with forest. With 7 billion people, you cannot sacrifice much of the arable land either.
Israelis have been reforesting their country for about 100 years and they have the best results on Earth (at least percentage-wise), but even they face bad odds in really dry places like the Negev desert.
