In 2014, the world emitted 10 billion metric tonnes of carbon dioxide. A 50 year old oak tree forest sequesters 30,000 pounds of CO2 per acre. At that rate of sequestration per acre, offsetting all carbon emissions would require 735 million new acres of trees, which sounds like a lot but is only about 2% of the world's total land area. By comparison, Europe is about 1490 million acres, and the United States is 2400 million acres.
Would it be practical / possible to offset global carbon emissions by reforesting 2-3% of the earth's land area, specifically in deforested regions? I know you can't just conjure up a 50 year old oak forest, but by choosing the right species of trees it should be possible.