SYDNEY (Reuters) - A huge outback dust storm swept eastern Australia and blanketed Sydney on Wednesday, disrupting transport, forcing people indoors and stripping thousands of tonnes of valuable farmland topsoil.
The dust blacked out the outback town of Broken Hill on Tuesday, forcing a zinc mine to shut down, and swept 1,167 km (725 miles) east to shroud Sydney in a red glow on Wednesday.
By noon on Wednesday the storm, carrying an estimated 5 million tonnes of dust, had spread to the southern part of Australia's tropical state of Queensland.
Dust storms in Australia are not uncommon but are usually restricted to the inland. Occasionally, during widespread drought, dust storms reach coastal areas. Australia is the driest inhabited continent and only Antarctica is drier.
Australia is battling one of its worst droughts and weather officials say an El Nino is slowly developing in the Pacific which will mean drier conditions for eastern states.
The country is one of the most vulnerable nations to climate change, but also the world's biggest greenhouse gas emitter per capita as it relies on coal-fired power stations for the bulk of its electricity.
Scientists are reluctant to directly link climate change with extreme weather events such as storms and drought, saying these fluctuate according to atmospheric conditions, but green groups link the two in their calls for action.
International flights were diverted from Sydney, ferries on Sydney Harbor were suspended and motorists warned to take care on roads because of poor visibility. The dust set off smoke alarms in some buildings in Sydney's central business district and halted construction.
Health authorities urged people to stay indoors, warning the storm was likely to continue into Thursday. More than 200 people called emergency services with breathing difficulties. The official air quality index for New South Wales recorded pollutant levels as high as 4,164 in Sydney. A level above 200 is hazardous. (here)
"People at risk are children, elderly, pregnant women, people with heart and lung diseases. Dust particles can increase the risk of people with these conditions becoming unwell," said Wayne Smith from the New South Wales state health department.
"EARTH, WIND AND FIRE"
The Bureau of Meteorology said a big cold front in New South Wales caused severe thunderstorms and gale-force winds, which whipped up the dust from the inland and spread it across Australia's most populous state. Winds of more than 100 km per hour also fanned bushfires in the state.
"This is unprecedented. We are seeing earth, wind and fire together," said Dick Whitaker from The Weather Channel.
New South Wales recently cut the state's 2009/10 wheat crop estimate by a fifth because of dry weather.
Sydney residents told local radio that they woke to scenes from a Hollywood apocalyptic movie, while many contacted emergency services fearing a big bushfire in the city.
Karen from Sydney's inner western suburb of Dulwich Hill said she woke up to find the red dust had covered her floors and birds had been blown out of their nests.
"It did feel like Armageddon because when I was in the kitchen looking out the skylight, there was this red, red glow coming through," Karen told Australian radio.
The blanket of dust affected most of New South Wales, the fifth-biggest state or territory representing 10 percent of the continent, and southern parts of Queensland state.
The dust storms stripped valuable topsoil from primary eastern farmlands. At one stage up to 75,000 tonnes of dust per hour was blown across Sydney and dumped in the Pacific Ocean, but the exact amount of dust dumped on Sydney was still being calculated.
"We've got a combination of factors which have been building for 10 months already -- floods, droughts and strong winds," said Craig Strong from DustWatch at Griffith University in Queensland.
"Add to these factors the prevailing drought conditions that reduce the vegetation cover and the soil surface is at its most vulnerable to wind erosion."
But crop analysts said the storm is unlikely to have an immediate impact on wheat crops, in the country's second-largest grain producing state, due to be harvested next month.
Further cold fronts are expected later in the week and could again whip up more dust storms, said weather officials. (Editing by Jan Dahinten)