Abstract
A collapse of the Atlantic Meridional Overturning Circulation (AMOC) leads to global cooling through fast feedbacks that selectively amplify the response in the Northern Hemisphere (NH). How such cooling competes with global warming has long been a topic for speculation, but was never addressed using a climate model. Here it is shown that global cooling due to a collapsing AMOC obliterates global warming for a period of 15–20 years. Thereafter, the global mean temperature trend is reversed and becomes similar to a simulation without an AMOC collapse. The resulting surface warming hiatus lasts for 40–50 years. Global warming and AMOC-induced NH cooling are governed by similar feedbacks, giving rise to a global net radiative imbalance of similar sign, although the former is associated with surface warming, the latter with cooling. Their footprints in outgoing longwave and absorbed shortwave radiation are very distinct, making attribution possible.
Highlights
Deep to the upper ocean, which occurs in narrow regions of convective mixing[12]
The impact of an AMOC collapse is analysed from an experiment in which persistent hosing, forcing the AMOC to remain in a collapsed state, is combined with increasing CO2 forcing, focusing on how they modify the ocean heat uptake and TOA radiation imbalances, and how these anomalies translate into different surface warming signals
The cooling resulting from an AMOC collapse can locally counteract for more than a century the global warming associated with increased greenhouse gas concentrations
Summary
Deep to the upper ocean, which occurs in narrow regions of convective mixing[12]. The strength of the heat pump is largely set by the AMOC, determining the ocean’s heat uptake efficiency during transient climate change[13]. In response to an AMOC collapse, net ocean heat uptake, that was already keeping the planet’s surface cooler than its equilibrium value associated with the increasing radiative forcing, is further enhanced (Fig. 1a).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
