For starters, humanity emits more CO2 than the combined mass of entire biosphere (every living organism, not just trees), every 10 years. Even if we were somehow able to cover all landmasses of Earth with trees (which we can't) and thus double/triple the biomass we would only set back the problem by a decade or two.
Second, trees are part of a cycle. They store the CO2 temporarily, then release it mostly back to the atmosphere -- very small part becomes soil.
Trees are not a magical solution that is somehow constantly sequestering CO2 from atmosphere. Trees store a bit of CO2 once and then it stops and can even easily be reversed (if you burn it down). New growth is necessary to keep the store at the same level, otherwise the trees will burn or die and CO2 is returned to the atmosphere.
It is actually very simple. Everybody can check easily. You do not have to believe me.
You need two numbers:
1. Amount of carbon emitted by humanity. The easiest way to get this is to find all production of coal, nat gas and oil and convert it to carbon.
2. Amount of carbon in biomass. You can find the estimate of weight of Earth's biomass online. Then you need to multiply by a factor of how much carbon there is in biomatter on average.
All necessary numbers are readily available and not controversial.
As to how much plants use CO2 it is IRRELEVANT. The only way it would be relevant is if you also had a number on how much plants emit CO2 back to atmosphere when they burn or rot. But this is extremely difficult to measure directly.
Just as you can't figure out how much you are saving up just based on your income without knowing your expenses.
But you do not have to estimate any of the two numbers. It is enough to imagine that, given constant weight of the biomass, all carbon converted from CO2 to biomass has also roughly equivalent release back to atmosphere one way or another.
For starters, humanity emits more CO2 than the combined mass of entire biosphere (every living organism, not just trees), every 10 years. Even if we were somehow able to cover all landmasses of Earth with trees (which we can't) and thus double/triple the biomass we would only set back the problem by a decade or two.
Second, trees are part of a cycle. They store the CO2 temporarily, then release it mostly back to the atmosphere -- very small part becomes soil.
Trees are not a magical solution that is somehow constantly sequestering CO2 from atmosphere. Trees store a bit of CO2 once and then it stops and can even easily be reversed (if you burn it down). New growth is necessary to keep the store at the same level, otherwise the trees will burn or die and CO2 is returned to the atmosphere.