What Net Zero CO₂ Actually Requires
Earth has been warmer than it is now, and its climate changed long before humans began burning fossil fuels. That fact does not settle the modern climate question. It makes the question more precise: what is forcing the present warming, and what follows when the dominant disturbance is the transfer of carbon from geological deposits into the atmosphere? The answer leads to a stricter definition of net zero than political slogans usually provide. Net-zero CO₂ is a balance between human emissions and human removals, but not every way of closing that balance is equally credible. Forest restoration, source capture and atmospheric removal all have legitimate roles. Their usefulness depends on gross emissions first falling far enough for the remainder to become limited, identifiable and matched by storage that lasts. A credible carbon ledger therefore begins with subtraction. Avoid emissions where practical, capture difficult process emissions where appropriate, and reserve atmospheric r...