Though the Asian Summer Monsoon (ASM) sets the rhythms of climate in many of the most densely populated regions in the world, current climate models still struggle to represent many aspects of the ASM and its interactions with other components of the climate system. Here, as part of the APARC Large Ensembles for Attribution of Dynamically-driven Extremes (LEADER) activity, we use historical and single-forcing simulations from the Large Ensemble Single-Forcing Model Intercomparison Project (LESFMIP) to evaluate simulations of the ASM and its changes over recent decades from the perspective of the monsoon overturning. We briefly outline common discrepancies in four key aspects of this overturning: (1) the location of peak low-level moist static energy; (2) the vertical distribution of deep convective heating; (3) the reversal of upper-level temperature gradients; (4) the extent and intensity of the upper tropospheric monsoon anticyclone; and (5) teleconnections with Indo-Pacific ocean variability. Examples of biases against reanalysis and observational benchmarks (representing model error) and model spread (representing internal variability) are set against the context of model-simulated forced responses to recent changes in aerosols, greenhouse gases, and land use change. The results illustrate the scale of uncertainties in evaluating the forced response of the ASM circulation to climate forcing.

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