By happy ending they mean less of a bad end. These kind of effects have to be modeled using feedback with threshold models. Such as when a specific value excee

By happy ending they mean less of a bad end. These kind of effects have to be modeled using feedback with threshold models. Such as when a specific value exceeds a threshold, another effect, typically next feedback step, is enabled. E.g. if temperature exceeds x, additional input of methane is added to atmosphere, if sea level exceeds y, then half of San Francisco has to move, if mean strength of storms exceeds z, ten global sea trade is reduced, if temperature exceeds w then droughts are increased etc. These are input to another feedback model which evaluates societal impacts. Unfortunately such models are very hard to evaluate numerically. It is semi-discrete nonlinear optimization. Very chaotic.