Law of hurricane power discovered

The intensity of hurricanes follows a simple mathematical law – a finding that could help us predict how they will respond to climate change.

Álvaro Corral of the Centre for Mathematical Research in Barcelona, Spain, and colleagues looked at records of hurricanes from four ocean basins around the world between 1966 and 2007. For each known hurricane, they calculated how much energy it released, based on the wind speeds and how long the hurricane lasted.

Regardless of region, the researchers found that the proportion of rarer, strong hurricanes to more frequent, weaker ones was always the same, regardless of the ocean basin. Only the very weakest and the very strongest hurricanes did not fit the pattern, called a power law.

The team also looked at the effect of sea surface temperatures on hurricanes. The proportion of weak to strong hurricanes in each year was similar whether the year was warm or cold, but more of the most powerful hurricanes were observed in warm years. They saw the same effect in years affected by the El Niño climate cycle.

Worse to come?

Controversy has raged for several years over whether climate change will increase the intensity of hurricanes. Corral says that the results hint that, as temperatures rise to levels humans have not experienced before, there will be more of the most powerful hurricanes. But he says it is difficult to say for sure. "We don't know what will happen if temperatures go higher than those we have had," he says.

James Elsner of Florida State University in Tallahassee, is less sanguine about the effects of climate change. "Their results show that you get more powerful hurricanes if the sea surface temperatures are higher," he says. He adds that our best theories of hurricane formation also predict that higher sea surface temperatures lead to stronger hurricanes.