Assessing the effect of AMOC-induced temperature patterns on the global social cost of carbon

A weakening of the Atlantic Meridional Overturning Circulation (AMOC) is often portrayed as economically beneficial - leading to a reduction in the social cost of carbon. The reduced social cost of carbon is attributed to the reduction of temperatures in large parts of the globe. However, the existing literature relies on integrated assessment models (IAMs) without an explicit representation of AMOC strength, and is therefore unable to consider the implicit AMOC weakening that is already included in projected temperature patterns. This study accounts for the amount of AMOC weakening that is implicit in pattern scaling procedures within the IAM when considering the effects of AMOC weakening. The implicit AMOC weakening is teased out from the pattern scaling as a function of global mean temperature change across CMIP6 models. Additionally, we recalibrate the temperature response to AMOC weakening at the country level by analysing simulations from the North Atlantic Hosing Model Intercomparison Project (NAHosMIP). The new temperature response, as well as four already implemented responses, are considered using the META IAM. We then analyse the change in social cost of carbon caused by AMOC weakening along seven different AMOC projections, taking into account the AMOC response implicit in pattern scaling. Overall, we find that AMOC weakening-induced temperature changes lower the social cost of carbon. Contrary to previous assumptions, this reduction in the social cost of carbon is driven only by global mean cooling, whereas the pattern of the temperature responses increases the social cost of carbon.