It would have been the AMOC, which is the most significant component of the overturning circulation system in the global ocean, and the one whose weakening would have a clearest and most immediate impact.
Unfortunately, predicting its behaviour is difficult, for a variety of reasons. However, that doesn't mean such predictions should not be made, nor that alarm bells shouldn't be rung when it appears that things might be going awry, especially given the AMOC's global significance. Surely we can agree that insisting on only considering dangers of which we are entirely certain is a foolish approach to risk management?
Unfortunately, predicting its behaviour is difficult, for a variety of reasons. However, that doesn't mean such predictions should not be made, nor that alarm bells shouldn't be rung when it appears that things might be going awry, especially given the AMOC's global significance. Surely we can agree that insisting on only considering dangers of which we are entirely certain is a foolish approach to risk management?