30 January 2014 — Cyclone activity in Australia is at its lowest recorded activity in 500–1500 years, according to a new tropical cyclone activity index, and climate change may be to thank.
Studies have predicted a reduction in the number of cyclones – though of increased intensity – in the Southern Hemisphere towards the end of the 21st century, but the new data, published in Nature, suggests that it is occurring much earlier than expected.
Previous understanding of climate change’s effects on cyclone activity had been limited by the short length of records (fewer than 50 years of data), however James Cook University’s Jordahna Haig and colleagues have provided a reconstruction of tropical cyclone activity in Australia over a longer period by analysing oxygen isotope composition in stalagmites. Because cyclones produce a distinct oxygen isotope signature, this data was captured in the layers of stalagmites.
The results revealed a pattern of repeated cycles of tropical cyclone activity, the most recent of which began around 1700AD, and a dramatic decline in activity after 1960 in Western Australia.
This is in contrast to the “increasing frequency and destructiveness of Northern Hemisphere tropical cyclones since 1970 in the Atlantic Ocean and the western North Pacific Ocean”, the study authors stated.
“The dramatic reductions in activity since the industrial revolution suggest that climate change cannot be ruled out as a causative factor,” the study authors noted.
They said the new index could be applied to other areas and lead to increased ability to “forecast future trends in tropical cyclone activity under changing climate conditions, given that it is now possible to discern natural variability from anthropogenically induced change”.
See the full paper.