Queensland's cycles of havoc

BUT devastating cyclones are no clear signal the climate pattern is changing.

queenslands cycles

IN the eerie pre-tropical cyclone twilight gripping north Queensland Jonathan Nott has a sense of foreboding as he secures his Cairns property in preparation for the big one that may arrive today when Cyclone Yasi roars ashore.

About 290km south at Pimlico in inner Townsville, Tony Raggatt recognises the growing excitement in his teenage daughters as they wait for Yasi to hit.

It was the same excitement he had felt 39 years ago in the same city, when as a 13-year-old always up for an adventure, he had told his father, then battening down the family home at North Ward near Townsville's beachfront, that he hoped the cyclone would come.

In the event Cyclone Althea did arrive the next morning, Christmas Eve, but while the experience was exciting it was far more frightening.

"One's enough for me. It was very scary indeed. Once you've been through one you don't want to go through another one," Raggatt says.

If the forecasts are accurate - and much can change in 24 hours - Cyclone Yasi will be one to remember.

Nott says Yasi could be the severest cyclone to directly affect Cairns since European settlement.

It could rival Cyclone Mahina in 1899, which hit land at Bathurst Bay north of Cooktown, destroying the pearling fleet and killing 400 people.

Given its width and intensity, Yasi could be worse than the twin cyclones of 1918, one of which put the central business district of Mackay under 5m of water.

But it would still not rival more extreme weather events, the evidence of which is still carved into the tropical landscape.

Nott is an expert on the incidence of super cyclones. By analysing ridges of broken coral pushed ashore by storm surges, he has catalogued the incidence of super-cyclones over the past 5000 years.

In a paper published in the scientific journal, Nature in 2001 his research shows the frequency of super-cyclones is an order of magnitude higher than previously thought.

Nott's work puts into perspective current debate about whether climate change is responsible for the extreme weather events in Queensland.

Over recent centuries, massive cyclones have been relatively common. And after an extended period of relatively little activity their return is overdue regardless of rising global temperatures.

Despite claims to the contrary, climate scientists say it is not possible say with any confidence whether there is a climate change signal in a single extreme event or even an extreme season.

"It is difficult to make a strong case that we are seeing a change in tropical cyclones," Bureau of Meteorology climate specialist David Jones says.

"There is a strong physical basis for expecting cyclones to become stronger but it is challenging to see a particular trend in the data," Jones says.

Most of the cyclone data used by climate scientists only dates back to the 1980s.

Prior to 1960 it was only really possible to measure cyclones opportunistically if they happened to pass over a boat or weather station.

From the late 70s to 80s the quality of data improved dramatically with the availability of very good satellite images.

According to Jones, the historical data was not sufficient to make concrete predictions. There is a clear link, however, between recent floods and cyclonic activity and the El Nino and La Nina weather patterns governed by Pacific Ocean surface temperatures.

The return of a La Nina weather pattern is a sure signal that tropical cyclone activity will intensify.

According to a paper by BOM Queensland weather forecaster Jeff Callaghan, the frequency of severe land-falling tropical cyclones had declined to low levels in recent decades in line with the El Nino weather patterns. Callaghan's analysis shows that landfalls occurred almost twice as often in La Nina years as they did in El Nino years and that more than one cyclone only ever hit land during La Nina years.

Callaghan says it would be imprudent to suppose the low number of tropical cyclones crossing the coast in recent decades would continue and planning should reflect the possibility of a rapid return to higher landfall rates.

Callaghan's research confirms Nott's analysis that tropical Australia is overdue for a dramatic intensification of cyclonic activity, regardless of whether there is a climate change signal in what is happening now or not.

"It is really difficult to say we are seeing a climate change signal," Nott says.

"No one in the climate change area is willing to say it is possible to see an anthropogenic impact in single event or even a season of events.

"There is no clear signal as yet but that does not mean it isn't affecting us."

What the longer term records show, however, is that the frequency of extreme cyclones follow a predictable long-scale pattern.

"What the record shows is we go through extended periods, hundreds of years, of high activity and extended periods of little activity," Nott says.

"The past 100 to 150 years has been very quiet in Queensland in terms of what happened in the past. The couple of hundred years prior to that were very active."

According to shorter term decadal scale-that uses a 10-year cycle- Queensland can also expect a big increase in the number of severe cyclones.

The Interdecadal Pacific Oscillation indicates the tropical north is due to emerge from a three-decade period of low cyclonic activity and return to the conditions of the 50s, 60s and 70s.

When Cyclone Althea hit in 1971 John Raggatt (Tony's father) recorded in his dairy that "by 2am the wind was gusting strongly. Outside, low white clouds raced in from the sea, silhouetted against a heavy black cumulus overhead. In the house the noise of the wind and rain competed with pop tunes and static from the radio."

The eye of Cyclone Althea crossed the coast some 20km north of Townsville, with its real intensity starting from about 7am.

At first, said Tony Raggatt, the sense of excitement was still there as the family looked out the window and saw houses on Castle Hill losing whole trees and sheets of iron running down the street.

"But it got really scary when things started happening inside the house. Firstly, the french doors blew in, so suddenly all this wind was inside the house. My father had to nail up a board across it.

"The the ceiling in the kitchen exploded under the pressure. It just broke up into little bits and fell onto the floor.

"So at that stage we just huddled under a mattress under a table. It was absolutely terrifying.

"Some memories never leave you. It's like it all happened in slow motion. I can remember bits of our roof blowing off and crashing into the neighbour's house, just like an explosion."

After two hours of terror the wind started slowly to abate from about 10am, but the family were still loath to move out from under their mattress, not convinced the worst had passed.

But at about noon, he and his brothers went for a walk along Townsville's Strand, which looks out towards Magnetic Island, and couldn't believe the devastation they saw.

Elsewhere in Townsville, Keith Bryson was calculating when he could get back to Magnetic Island.

Bryson, who runs an oyster farm on the island, had the day before taken his 9m boat from Magnetic Island into Townsville to try and save it from the cyclone, having done his best to secure his other, smaller boat.

"Never saw it again," he says. "Probably just smashed up somewhere."

He got his bigger boat into anchorage up the Ross River in Townsville, although he had to jostle for position.

"There were a lot of boats coming in then, just yachties up the coast, fishermen. We all knew it was coming."

While Magnetic Island is just off Townsville and is now a commuter suburb, in the early 70s it was quite cut off, and there were no regular ferry services.

Bryson had listened to the radio-a common theme among all who lived through Cyclone Althea was that the radio station kept broadcasting - and knew that the cyclone was coming.

"I got everything up off the beach, but after the cyclone went, I went down and checked the oysters-I didn't lose any."

He thinks this shows that while the wind whipped up the water on top, underneath it was calmer and the sort of storm surge which led to floods in Townsville was a steady and sustained surge rather than a whirlpool.

Yesterday, he found himself down on the beach again on Magnetic Island, picking up ropes and other materials associated with oyster farming and battening down for another cyclone.

"I'm 88 now - I didn't think I'd still be doing this. But if you've been through one cyclone, you don't want to go through another."

The experience of sitting through a cyclone proved to be a career changer for George Walker, who arrived in Townsville as a young engineer in the late 60s to work as a structural engineer.

He'd got an early taste of what a cyclone in tropics was like, going to Proserpine and Airlie Beach in 1970 after Cyclone Ada had ripped through.

He saw enough of what a cyclone can do to attach firm brackets to his house in Aitkenvale in suburban Townsville, a measure that stood him in good stead when Althea arrived a year later.

"I had taken some precautions - I had hammered up the doors with a piece of four-by-two, and put the brackets on. I firmly believe those brackets stopped the roof coming off in that cyclone."

Walker, now semi-retied to Queensland's Sunshine Coast but still an adjunct professor at James Cook University, found himself in Townsville yesterday for a previously scheduled round of meetings.

"I should stay away from the place, I think I'm bad luck," he joked.