Tasmania's bushfire frequency highest in 1,000 years: Aussie study

Researchers have found that bushfires in the Australian state of Tasmania are occurring more frequently than at any time in the past 1,000 years, and humankind is to blame.

As more than 40 bushfires continue to burn across Tasmania, most of which are now contained, scientists on Wednesday attributed the state's proliferation of fires to a shift in wind direction caused by human-induced climate change.

"My conviction is that the current trend is evidence of anthropogenic forces," Doctor Michael-Shawn Fletcher of the University of Melbourne told the Australian Broadcasting Corporation (ABC) on Wednesday.

The team from the University of Melbourne looked at Tasmania's wind index known as the Southern Annular Mode (SAM) which tracks major changes in wind direction and its relation to overall rainfall.

During a negative SAM, westerly winds move north, while during positive SAM the winds move south bringing drier conditions on land.

Previous research has made the link between the prevalence of a positive SAM and the area's diminishing ozone layer, which affects the upper atmosphere.

The Melbourne scientists analyzed coal deposits from Tasmanian fires, including blazes burning at present, over the past 1,000 years and discovered there was more of the black substance during positive SAM periods.

"Correlation isn't causation," Fletcher, who studies long-term interactions between humans, climate and vegetation, told the ABC.

"But it's a well-described phenomenon that ozone depletion has caused a positive trend in SAM and we've got clear evidence that the SAM index in the 21st century has exceeded anything that's occurred in the last 1,000 years."

Fletcher said the amount of charcoal at any particular fire would rise or fall based on the SAM index.

According to the researchers, the SAM index and bushfire coal mass have been gradually climbing since the 1500s and have spiked again in recent times. Endit