An index of the sensitivity of surface fluxes to soil moisture variations is defined that elaborates on the correlation between soil moisture and fluxes to include the magnitude of the forced variations of fluxes across typical ranges of soil moisture variability. This index better represents the strength of the terrestrial segment of the feedback pathway from soil moisture to climate than correlations alone. Maps of this sensitivity index show strong agreement with “hot spots” of land-atmosphere coupling and land-driven predictability enhancement found in other studies. The index is found to be robust across data from land surface models driven by observations and free-running global coupled land-atmosphere models, but is compromised in reanalysis data due to inflated interannual variability in soil moisture caused by non-stationarity in the satellite observing system that is used in data assimilation. The index can be calculated from daily observations or model output of sufficient length to ensure statistical significance of results.