How does the frequency of hurricane formation change with climate?

How does the frequency of hurricane formation change with climate? The recently increase in hurricane activity has brough increased attention to the realtionship between global climate, hurricane intensity, and hurricane frequency. There is evidence that increases in sea surface temperature (SST) expected from the current climate trends will lead to modest increases in the duration and intensity of tropical cyclones, although considerable uncertainty and debate remains. Whether or not there will be more or less hurricanes in a warmer world is even less certain.

Our current research uses high-resolution numerical model simulations to assess whether or not increasing SST leads to a greater likelihood on cyclone formation. Our working hypothesis is that higher SSTs lower the threshold intensity necessary for a tropical "disturbance" to transition to a warm-core, tropical cyclone. This hypothesis is summarized in Figure 1. For high enough temperatures at high enough latitudes, cyclones can form from random convection. This has been supported by numerical simulations which show "spontaneous" cyclogenesis from radiative-convective equilibrium over SST of 30 celsius at 40 degrees N latitude. The evolution of the convection (vertical motion) the simulation is shown in Figure 2.

Figure 1

Figure 2