Drastic increase in economic damages caused by a marginal increase in CO2 emissions?

When economists estimate the expected economic damages from current-day CO₂ emissions, they usually calculate the social cost of carbon – that is, the aggregated damage caused by the emission of an additional ton of CO₂. Several cost-benefit integrated assessment models (IAMs) are built to assess this quantity, and among them is the META model. This model is built specifically to assess the effects of tipping points on the social cost of carbon, and it usually operates stochastically. When integrating a deterministic, but small carbon cycle tipping point into the model, however, the social cost of carbon seems to explode: a few gigatons of additional emissions almost double the impact estimates of CO₂ emissions! Well, maybe. In fact, these results are a pure artifact of two things: 1) the way in which social cost of carbon estimates are calculated with IAMs; and 2) the way that tipping points are implemented in the META model. And, of course, 3): a lack of initial thoughtfulness on behalf of myself. A thorough look into this issue shows that, as expected, a marginal change in emissions leads to a marginal change in damage estimates. While that result is rather boring, the previous blunder can actually be instructive about the scarcely-known methods used to obtain economic impact estimates of climate change.