First author

Recent research suggests that human-induced increases in sea-surface temperature may cause more frequent intense hurricanes (for example, see Nature 436, 686–688; 2005). On page 465, Jeff Donnelly and his colleague Jonathan Woodruff of the Woods Hole Oceanographic Institution in Massachusetts report their use of sediment samples from an inland lagoon on the island of Vieques, Puerto Rico, to show that active hurricane periods also occurred during cooler periods. The Caribbean cores provide a 5,000-year record of both frequent and infrequent hurricane periods.

Describe what an intense hurricane looks like in the sedimentary record.

Intense storms cause surges and waves that can overflow the beach. We look for evidence of storm surges inland, where waves have deposited sand and gravel into the muddy environment behind the beach. At times of more extreme hurricane events the dark organic-rich lagoon sediments contain light coarse-grained layers.

How did you decide to use the sedimentary record to understand hurricane activity?

I started taking cores to study salt-marsh vegetation changes over time, and found evidence of past hurricanes in the sediment record. After Hurricane Andrew in 1992, the reinsurance industry contacted us to use our cores to reconstruct the frequency of extreme events over a longer time period.

What were the most surprising results?

The recent active period started about 300 years ago, during the Little Ice Age. We didn't expect to see an increase in intense hurricane activity during this interval.

Could your results be misinterpreted?

I am worried about that. Our results don't mean that sea-surface temperatures are not a major player in driving intense cyclones. But other factors are also important. If sea-surface temperatures continue rising, this could provide more fuel for intense tropical cyclones. And, if such increases were combined with other conditions favourable for hurricane development — for example, fewer El Niño events and a stronger African monsoon — we could see an active regime unparalleled in the past few thousand years.

Are you working on other sediment cores to complete the story?

We're working all over the planet. We're doing more studies in the Caribbean and in the northeastern United States to understand hurricanes. And we've just started work in the Pacific, where little work has been done reconstructing typhoons.