Recent investigations using best-track data sets and potential intensity climatology show that the probability distribution functions of tropical cyclone intensity normalized by potential intensity appear to be universal. This means that the long-term climatology of tropical cyclone intensity is directly related to potential intensity, so that the latter is useful for quantifying the dependence of tropical cyclone intensity on climate. Here we explore the influence of various climate processes on potential intensity. One surprising result of this study is that variations of the radiative-convective equilibrium state with modest increases in greenhouse gases have a negligible effect on potential intensity, while quite modest changes in the strength of the Hadley-Walker circulation have a comparatively large effect on intensity. We postulate that the noticeable increase in tropical cyclone intensity reported in recent GCM-based global warming simulations is an indirect effect arising from increases in the strength of the Hadley-Walker circulation.