Herald Scotland

by Kathy Marks

As the final splutter of Cyclone Yasi triggered thunderstorms and flash floods in Melbourne this weekend, Australians were wondering what nature will throw at them next.

A monster category-five storm, Yasi smashed into north Queensland just weeks after the state endured the worst floods in its history.

Victoria, too, has been inundated. Yet it was only last year that south-eastern Australia emerged from its most crippling drought in more than a century, and the south-west is still bone-dry. Two years ago tomorrow, 173 people died in the nation's deadliest bushfires.

While Australia – the world's driest inhabited continent – may have had more than its share of natural disasters lately, climate scientists point out that it has always been a country of extremes.

However, they also say that those extremes are, in all likelihood, being exacerbated by global warming, and they warn that the havoc wreaked here recently represents a snapshot of the future, not just in Australia but around the world.

The pattern is already established: according to data collected by the Munich RE reinsurance company – the industry has more interest than most in assessing climate-related risks – the number of such events has risen from 400 in 1980 to more than 800 in 2008.

"A lot of people are putting their head in the sand and saying these are all one-offs," said Edward Blakely, professor of urban policy at the University of Sydney's United States Studies Centre. "How many one- offs does it take to make a trend?"

The largest and most powerful cyclone ever to cross the Queensland coast, with a 300-mile front and core winds of up to 180mph, Yasi would have had a catastrophic impact had it not, by good fortune, skirted the cities of Cairns and Townsville. Instead, it confined itself to destroying several small coastal towns, leaving just one person dead.

Frightening as Yasi was, it could be dwarfed by future storms, according to the Australian government's chief adviser on climate change, Ross Garnaut. Last week, as Queenslanders surveyed their wrecked homes, he warned: "If we are seeing an intensification of extreme weather events now, you ain't seen nothing yet."

With its natural climate variability, Australia is considered particularly susceptible to climate change – perhaps more so than any other developed country. The predictions are that its tropical north will become hotter and wetter, with more floods and more intense cyclones, while the south – where most people live – will become hotter and drier, suffering more droughts, heatwaves and bushfires.

Scientists caution against reading too much into any single weather event, and they say the main influence on the Australian climate is the El Nino/La Nina system, which is governed by surface temperatures in the Pacific Ocean and is responsible for wild weather in many parts of the world. However, they also note that the world has become hotter, and suggest climate change may be accentuating its effects.

Cyclone Yasi, and the monsoon rains that have drenched Queensland, setting off the country's worst floods in about a century, have been blamed on the strongest La Nina for nearly 40 years.

"The temperatures in the Pacific are anomalously warm, and the only explanation we have is in part a global warming signal," said Professor Andy Pitman, of the Climate Change Research Centre at the University of New South Wales.

He adds: "The scale of the flooding, the intensity and size of this cyclone, and all the other events going on around the world with increasing frequency – there's good evidence to suggest they are real-world examples of what the climate scientists have been predicting for some decades."

Others point to the bushfires, which raged through townships in hills north of Melbourne in February 2009. The fires were preceded by a record heatwave: a fortnight of sky-high temperatures that peaked at 46.4˚C (115.8˚F) on what Locals dubbed "Black Saturday".

There is less certainty about the cause of the 12-year drought, which threatened the future of the 386,000-square-mile Murray-Darling Basin, the source of nearly 40% of Australia's fresh food. But the government's main scientific body, the Commonwealth Scientific and Research Organisation, say there is growing evidence that lower rainfall in south-eastern Australia is linked to climate change.

While, for some, the floods have almost erased memories of the drought, the horrors of Black Saturday are engraved on the national psyche. Such destructive fires, though, are expected to become more common as southern Australia becomes hotter and drier.

This weekend New South Wales is on bushfire alert following its most sweltering heatwave for 150 years: six consecutive days of temperatures in the high to mid-30s Celsius, peaking at 41.5˚C in Sydney yesterday.

The records keep tumbling. When the drought broke last year, it did so in spectacular fashion: 2010 was Australia's second-wettest year. The exception was the south-west corner of Western Australia, which is still deep in drought and had its driest year ever.

Aggravating the situation are factors such as poor urban planning, with development permitted in areas historically vulnerable to flooding. "We've been living dangerously, and when you live dangerously, there's always a price to be paid," said professor Blakely.

While the impact of climate change on Australia may not be as dramatic as in nations such as Pakistan, Dr Karl Braganza, a senior climatologist with Australia's met office, said it was an ideal place to monitor the effects because it kept very good data compared with other tropical countries.

For Braganza, Cyclone Yasi and the floods are a reminder of the human cost of extreme weather. He and other scientists are already wondering how many more natural disasters it will require before decisive action is taken to reduce global carbon emissions.

In Australia, while there is, understandably, much hand-wringing about recent events, there is next to no debate about the role of climate change. Visiting north Queensland last week, the Prime Minister, Julia Gillard, declared: "We will rebuild from the floods, we will rebuild from the cyclone, we will rebuild from anything nature throws at us."

It was a response that dismayed professor Pitman. "There's an assumption that we can engineer our environment to be safe from whatever nature throws at us," he said. "I think these are flawed assumptions."