Hurricanes have long been considered freaks of nature, responding passively to regional climate variability. Although strong empirical relationships have been established between tropical cyclone activity and regional climate signals such as ENSO, the physics behind such relationships are not fully understood, and the subject is not sufficiently advanced that there is even a first-order theory to explain why there are about 90 such events globally each year. In this talk, I will review what current research is revealing about the control of tropical cyclone activity by regional and global climate, and discuss various controversies surrounding the nature of these relationships and how such controversies might be resolved in the next few years. I will also present new evidence that tropical cyclones are far from passive players in global climate, arguing that they collectively supply much of the upper ocean mixing that drives the oceans' thermohaline circulation.