All climate models project a weakening of the Atlantic Meridional
Overturning Circulation (AMOC) strength in response to greenhouse gas
forcing. However, the climate impacts of the AMOC decline in relation to
other drivers of climate change, cannot be assessed from existing
Coupled Model Intercomparison Project (CMIP) simulations. To address
this issue, we conduct idealized experiments using the EC-Earth3 climate
model. We compare an abrupt 4xCO2 simulation with an identical one,
except we artificially fix the AMOC strength at preindustrial levels.
With this design, we can formally attribute differences in climate
change impacts between these two experiments to the AMOC decline. In
addition, we quantify the state-dependence of AMOC impacts by comparing
the aforementioned experiments with a preindustrial simulation in which
we artificially reduce the AMOC strength. Our findings demonstrate that
AMOC decline impacts are state-dependent, thus understanding AMOC
impacts on future climate change requires targeted model experiments.