Understanding long-term variability in the occurrence of tropical cyclones
that are of extreme intensity is important for determining their role in ec
ological disturbances(1-5), for predicting present and future community vul
nerability and economic loss(6) and for assessing whether changes in the va
riability of such cyclones are induced by climate change(7). Our ability to
accurately make these assessments has been limited by the short (less than
100 years) instrumented record of cyclone intensity. Here we determine the
intensity of prehistoric tropical cyclones over the past 5,000 years from
ridges of detrital coral and shell deposited above highest tide and terrace
s that have been eroded into coarse-grained alluvial fan deposits. These fe
atures occur along 1,500 km of the Great Barrier Reef and also the Gulf of
Carpentaria, Australia. We infer that the deposits were formed by storms wi
th recurrence intervals of two to three centuries(8-11), and we show that t
he cyclones responsible must have been of extreme intensity (central pressu
res less than 920 hPa). Our estimate of the frequency of such 'super-cyclon
es' is an order of magnitude higher than that previously estimated (which w
as once every several millennia(12-14)), and is sufficiently high to sugges
t that the character of rainforests and coral reef communities were probabl
y shaped by these events.