It is possible the huge dust cloud over the UAE is the result of the war in Iraq, where years of troop and vehicle movement have pulverised the soil.
Opinions differ on cause of UAE dust
This is the dust cloud that has been blighting the UAE, as seen from space. The image was captured 700km away by a Nasa satellite, Terra. It shows an enormous concentration of dust heading towards the UAE from Iraq on Friday.
Launched in December 1999 as the flagship of the Earth Observing System project run by America's National Aeronautics and Space Administration, Terra has been gathering information as part of the battle against global warming. What it captured in this image, experts say, is incontrovertible evidence of man's harmful impact on the planet. The picture was taken by Terra's Moderate-Resolution Imaging Spectroradiometer - Modis, for short - which can view the entire surface of the planet every two days.
The size of the cloud was unusual, experts said. "This is a recent phenomenon," said Adnan Akber, a researcher in the water resources division of the Kuwait Institute for Scientific Research. "This year, in particular, we are receiving intensive dust storms that are also affecting you in the UAE." Such storms have a complex set of causes, but the main factor, according to Mr Akber, is perhaps the most surprising.
There have been many geopolitical consequences of the 2003 invasion of Iraq - and now part of the fallout can be found in the orange dust coating cars all over the UAE, he said. "If you're asking what the major cause of the dust is in the UAE, I would have to say the military operations in Iraq are really changing the surface terrain there," he said. Six years of troop and vehicle movements had, he said, ground soil into fine grains, sending powder billowing skywards.
"What that movement does is it disintegrates the soil particles, which, in the past, were naturally compacted," he said. "Now those particles are being loosened, so it's easier for that dust to be picked up." Mr Akber also pointed to a second year of drought in Iraq, compounded by the lowering of water levels in the Tigris and Euphrates Rivers by damming and irrigation projects upstream in Turkey and Syria, which had contributed to the arid conditions in Iraq.
Nasa's analysis of the dust cloud image concurred with several of his conclusions. It said: "Some causes included regional drought, water diversion, desertification and power shortages that interfere with irrigation systems. The combination of factors led to a build-up of dust in Iraq that could be lofted into the atmosphere by even slight winds." Other experts say military action may not necessarily be the primary cause of the dust.
According to the US military's Iraq weather office, while an average dust storm stays at 1,500 metres or less, some dust storms in northern Iraq last year reached 5,500 metres. Air Force Lt Col Jeffrey Cox told the US Army's Military News in July last year that the incidence of dust storms had been three times the average.
"We have lots of fine dust that gets picked up by the winds here, and since it is so fine, it takes a while to settle down," he said. Fadhil Faraji, director general of the Iraqi Agriculture Ministry's Department for Combating Desertification, told the Los Angeles Times last week that 90 per cent of the country's land was desert, or becoming desert, and what was left was disappearing at a rate of five per cent every year.
"Severe desertification is like cancer," he said. "When the land loses its vegetation cover, it's very hard to get it back." According to Awn Abdullah, head of the National Centre for Water Resources Management, part of the problem was that Turkey and Syria, which are suffering their own water shortages, had reduced the flow of the Euphrates by half. Ahmed Habib, an Abu Dhabi-based weather forecaster with the National Meteorological Centre, said low pressure and light winds were keeping the dust suspended over the UAE.
"I don't know what happened in Iraq, but the quantity of the dust coming from Iraq is increasing," he said. Stronger winds lifted the haze and dumped it on the UAE last week. "Now we are having a low-pressure effect, so the dust stands over us and is moving very slowly," Mr Habib said. Visibility is improving, however. On Sunday, it was down to 300 metres in places. Yesterday, it was between 2,000 metres and 5,000 metres.
"We will have a normal haze on Wednesday," he said. "Not clear 100 per cent, but it will be better and there should be no warnings for anybody." Lack of rainfall in Iraq for the past two years had compounded the man-made problems, according to a duty forecaster for the Dubai Meteorological Office. "It's made it relatively easy for dust to get lifted with strong winds over that region," he said. "Strong winds are able to lift dust high in the air, carry it along and dump it over us."
Much of the orange sand caked on car windows here, he said, had travelled at least the length of the Gulf. "This dust is very definitely not from here," he said. "It originated over in Iraq." While the north-westerly winds - shamal - were stronger last week as they funnelled into the Gulf, their power had weakened over the UAE. "By the time the wind gets here, the strength is diminished and it's almost a stagnant situation, where the dust cloud is sitting on top of us, but there's not enough wind to blow it someplace else," said the forecaster.
Dr Tarek el Araby of the Norwegian Institute for Air Research, which runs Abu Dhabi's air-quality monitoring network on behalf of the Environment Agency, said the danger of the cloud laid in the unusually minute size of the particles. Small particles of dust, smoke, heavy metals, spores and pollen are present in the air every day. A concentration higher than 150 micrograms per cubic metre over 24 hours is deemed risky, but last Saturday amounts greater than 2,000 micrograms per cubic metre were recorded.
The concentration was decreasing, said Dr el Araby, but breathing outdoors still carried considerable risk, especially for children and people with respiratory illnesses. "It is now at 1,500 micrograms per cubic metre," he said. "It is not so dangerous as people do not spend the whole day outside, but it is very important for everyone to know that you should stay indoors and limit all outdoor activities."
Particles smaller than 2.5 micrometres can travel deep into the lungs, where they can cause diseases such as emphysema and cancer. Although the data available for Abu Dhabi at the moment show only the cumulative concentration of all dispersed particles, Dr el Araby said the concentration of these smaller but more dangerous particles is also high. "They are usually a quarter of the total," he said.
Doctors urged asthmatics to avoid the dusty conditions as much as possible. In six days, Al Qassimi Hospital in Sharjah had admitted 60 patients suffering asthma attacks, said Dr Fatimah Ibrahim, the manager. * The National, with additional reporting from Yasin Kakande