Preserving the ocean circulation: Implications for climate policy

Climate modelers have recognized the possibility of abrupt climate changes caused by a reorganization of the North Atlantic's current pattern (technic ally known as a thermohaline circulation collapse). This circulation system now warms north-western Europe and transports carbon dioxide to the deep o ceans. The posited collapse of this system could produce severe cooling in northwestern Europe, even when general global warming is in progress. In th is paper we use a simple integrated assessment model to investigate the opt imal policy response to this risk. Adding the constraint of avoiding a ther mohaline circulation collapse would significantly reduce the allowable gree nhouse gas emissions in the long run along an optimal path. Our analysis im plies that relatively small damages associated with a collapse (less than 1 % of gross world product) would justify a considerable reduction of future carbon dioxide emissions.