Forest fires come in many forms, from a small grass burn to a firestorm. But they have no "typical" size: small fires are always far more numerous than large ones, and this rule holds in any forest. Tropical cyclones behave the same way. Scientists measured the energy of hundreds of hurricanes in four oceans and found that weak storms are plentiful, strong ones are rare, and the proportion is always the same.

Warm years and the El Niño current allow more powerful hurricanes to form. But the overall picture does not change: it is as if the climate merely stretches the ruler rather than changing its markings. This means the atmosphere resembles a pile of sand onto which grains are poured: it is impossible to predict which grain will trigger an avalanche. Therefore, an accurate forecast of hurricane intensity will always be difficult.