Uncertainty Quantification of the regional temperature consequences of a large AMOC decrease and use in AMOC scenario exploration

This study performs uncertainty quantification on the regional mean surface temperature response to changes in the Atlantic Meridional Overturning Circulation (AMOC) and allows the investigation of novel AMOC scenarios. ESMs/GCMs primarily show gradual AMOC slowdown in the 21^st and early 22^nd century while other approaches suggest that a “tipping point” may be present which could lead to faster decline in the AMOC during this period. This study aims to estimate the impacts of a rapid decline or other AMOC scenarios and the range of possible outcomes which can be inferred from the current ensemble of climate models and approaches.  Changes in temperature and AMOC will be analysed under a range of forcing scenarios including CMIP6 SSP scenarios for global warming, freshwater hosing scenarios from NAHosMIP, and ClimTip runs showing a combination of global warming and freshwater hosing. The relationships between AMOC change, global mean surface temperature and regional mean surface temperature are described, as well as our uncertainty in these values based on the model ensembles.  These relationships are used to generate annual mean regional/ national temperature trajectories under a range of potential AMOC scenarios, with uncertainty ranges given for each scenario and location. These methods can be extended to both seasonal temperature and annual precipitation, and the data produced is highly consequential for economic impact assessments and adaptation planning.