Henry's Law

The chemistry principle that the concentration of a gas dissolved in a liquid is proportional to the partial pressure of that gas above the liquid. The book applies Henry's Law to atmospheric CO₂: when concentrations fall during the removal era, the ocean will release stored CO₂ back into the atmosphere to maintain equilibrium. This means carbon removal infrastructure must run faster than the ocean can outgas, and it sets the lower bound on how quickly atmospheric concentrations can be drawn down.