Hurricane intensity linked to climate change
The number of high-strength cyclones, like Hurricane Katrina, has nearly doubled in 35 years in all five of Earth's ocean basins, which scientists said today could be linked to global climate change.
"Global data indicate a 30-year trend toward more frequent and intense hurricanes," said the researchers from the University of Georgia and the National Centre for Atmospheric Research at Boulder, Colorado.
However, scientists said they lacked enough data to be definitive, because the period studied in the report released today was too short.
Meanwhile, other factors, such as El Nino current or humidity play a role in the intensity of tropical storms, they said.
They noted a strong uptick in the number and proportion of storms in the top two Saffir-Simpson levels, categories four and five, has been constant from 1970 to 2004, especially in the Indian and the North and South-west Pacific Ocean basins. The rise has been less in the North Atlantic.
Around the world, the number of tropical hurricane days rose regularly from 1970 to 1995, when it levelled off at 870 hurricane days, then dropped by 25 per cent until 2003, to 600 days, the scientists said.
Scientists have largely accepted that Earth's climate has been warming since the beginning of the 19th century amid the burning of fossil fuels, which give off carbon dioxide. As CO2 accumulates in the atmosphere, it blocks the sun's reflected rays from returning to space, much as glass keeps a greenhouse warm.
While the so-called greenhouse effect has always existed, scientists fear that CO2 emissions are causing polar ice caps to melt and cyclones to become stronger.
"Attribution of the 30-year trends to global warming would require a longer global data record and, especially, a deeper understanding of the role of hurricanes in the general circulation of the atmosphere and ocean, even in the present climate state," they said.