What sets the number of tropical cyclones Earth has each year?
In plain words
Earth has about 80 to 90 hurricanes and typhoons a year, and this number has stayed roughly steady for decades. No theory explains why it is this number and not 10 or 1000, or how it will change with warming.
Precise statement
Derive the global annual tropical cyclone frequency (about 85 per year) from the large-scale state, specifying whether genesis is limited by the rate of seed disturbances or by environmental conditions, and predict its sign and magnitude of change under CO2 doubling. An answer is a theory or validated genesis index that reproduces present climatology and agrees with convection-permitting simulations across climates.
What would settle it
A genesis theory whose predicted frequency changes match convection-permitting global simulations across a range of imposed climates and the observed interannual record.