Effects of Spatial Patterns of Ocean Heat Uptake on the Intermodel Spread of the Transient Climate Response

A pressing goal of climate science is to reduce the uncertainty in climate sensitivity to anthropogenic forcing, with far reaching implications for science and policy. Recent advances have shown that feedbacks processes governing the transient climate response (TCR) are strongly influenced by the spatial pattern of ocean heat uptake (OHU). This work seeks to determine how much of the spread in TCR in the CMIP5 ensemble can be attributed to inter-model variations in OHU rather than structural differences in modeled radiative feedbacks. We assess this by using a single model (a slab-ocean version of the Community Earth System Model) forced by an ensemble of OHU patterns diagnosed from CMIP5/6 transient warming experiments. We find that the spread in OHU captures a significant portion of the CMIP5/6 spread in TCR, with the large variability in North Atlantic OHU playing the greatest role in setting the response. Radiative kernel analysis provides some new insight into how these OHU patterns project on climate feedbacks.