Carbon embodied in wood is current-cycle carbon, it's already part of the biosphere. In most cases, it was sequestered from the atmosphere at most a few decades ago, for the very oldest trees, a few centuries (and most of those aren't burned for fuel).
Carbon embodied in coal, oil, and gas was last part of the biosphere hundreds of millions of years ago. And that's precisely the problem: humans have re-introduced, mostly in the past 50 years (95% of all oil was burned since then, a large portion of coal and gas) carbon that was deposited over hundreds of millions of years. The biosphere portion of the carbon cycle (atmospheric uptake, oceans, plant growth) simply cannot keep up.
Yes, if you were to burn all forests at once, you'd run up CO2 a bit. That is, however, a pretty self-limiting prospect.
Carbon embodied in coal, oil, and gas was last part of the biosphere hundreds of millions of years ago. And that's precisely the problem: humans have re-introduced, mostly in the past 50 years (95% of all oil was burned since then, a large portion of coal and gas) carbon that was deposited over hundreds of millions of years. The biosphere portion of the carbon cycle (atmospheric uptake, oceans, plant growth) simply cannot keep up.
Yes, if you were to burn all forests at once, you'd run up CO2 a bit. That is, however, a pretty self-limiting prospect.