As far as trees go, how many decades can you increase tree biomass continuously 1.5% year on year? Where does the extra land to do this come from? How do we build new land that can effectively grow new trees? It's fine, as far as it goes, but we'll run out of trees to plant long before we run out of fossil fuels to burn.
Phytoplankton stimulation is a lot better, in that we can do it year on year. Indeed, it can, optimistically, remove around a billion tons of CO2 per year from the atmosphere, with advancements in technique and extremely widespread use, for a relatively low cost.
Humans emit roughly 40 billion tons of CO2 per year into the atmosphere, though. Year on year, we add roughly a billion tons of CO2 emissions to our annual emission rate.
We can go into even more exotic methods if you like. But if governments are unable to implement a tax on carbon that accounts for its externalities, why do you think governments would be willing to pony up even more money to sequester those externalities after the fact?
This xkcd comic is based in poor data, probably. Rats and domestic mice don't appear on it. Cats and dogs should appear also (and be in a big group). I would take it with a pinch of salt.
Phytoplankton stimulation is a lot better, in that we can do it year on year. Indeed, it can, optimistically, remove around a billion tons of CO2 per year from the atmosphere, with advancements in technique and extremely widespread use, for a relatively low cost.
Humans emit roughly 40 billion tons of CO2 per year into the atmosphere, though. Year on year, we add roughly a billion tons of CO2 emissions to our annual emission rate.
We can go into even more exotic methods if you like. But if governments are unable to implement a tax on carbon that accounts for its externalities, why do you think governments would be willing to pony up even more money to sequester those externalities after the fact?