Speaker: Chengfei He
Earth system models well simulate global mean sea surface temperature (SST), but the spatial pattern of SST change remains poorly constrained. In this talk, I will show that the atmosphere plays a leading role in shaping two prominent features of SST pattern. First, the North Atlantic warming hole, widely viewed as a fingerprint of the declining AMOC, can be largely reproduced in a model without ocean circulation, driven by strengthened westerlies that enhance ocean heat loss. Second, CMIP6 models simulate a positive trend in the interhemispheric thermal contrast (IHTC) since 1950, opposite to the observed negative trend. Models respond mainly to greenhouse gases, which warm the NH through wind–evaporation–SST feedback, whereas the real world has been dominated by aerosol forcing. This discrepancy suggests that real-world climate sensitivity may be lower than CMIP6 projections. Nevertheless, models capture the multidecadal IHTC variability well, enabling a novel constraint on aerosol–cloud radiative forcing.
This seminar can also be viewed via our live stream.