Funded by the National Science Foundation as well as CMI, Klaus Keller is analyzing designs of scientific observation systems that could provide actionable early warning signs of potential climate threshold responses. One such threshold response involves a collapse of the North Atlantic meridional overturning circulation (MOC), the “ocean conveyor belt” that transports heat from low latitudes to the North Atlantic basin and the surrounding regions. The MOC has collapsed in the past, causing widespread and sudden climatic changes. Model simulations suggest that anthropogenic greenhouse gas emissions may trigger an MOC collapse in the future. These model predictions, however, are deeply uncertain.

The project has already shown that a continuation of the currently implemented and well-tested observation strategy, based on relatively infrequent and uncertain observations, is likely to fail at the task of early detection; confident detection of potential MOC changes might occur only after the threshold has been triggered. A feasible system with more frequent and less uncertain observations could deliver an early, confident, and reliable detection of anthropogenic MOC changes.

The analysis by Keller and colleagues suggests that reducing the odds of an MOC collapse (e.g., down to 1 in 10) would require a considerable decarbonization of the world’s economy on a timescale of decades. Reducing the current uncertainty (for example through investing in an ocean observation system) can provide considerable net economic benefits, as it enables the design of more focused risk management strategies. This approach quantifies the net economic benefits of investing in uncertainty reduction.