There is no doubting the severity of the dust storm which caused chaos across Tehran on Monday evening. A wall of desert dust rolled across the city, blown by winds of at least 110kph, but reported to be as high as 130kph by the country’s official IRNA news agency.
Trees and power lines were felled and many traffic accidents were reported on a road south of Tehran. At least four people are known to have died and there were reports of at least 30 injuries. Flights from the international airport were cancelled.
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Dust storms have always been a regular occurrence but there is evidence that they are happening much more frequently. In 2013, 23 of the country’s 31 provinces were affected by dust storms. Tehran experienced dust clouds on 117 days.
Iran is part of the Northern Hemisphere’s ‘dust belt’ which extends from North Africa, through the Arabian Peninsula, to southern and central Asia.
Winds blowing across the country’s open plains pick up loose soil and sand and may carry it for thousands of kilometres.
The dust causes severe air pollution with the attendant risk to public health. Machinery can become clogged and road, rail and air transport are severely hampered.
These storms are a natural result of weather patterns, reaching a peak during the spring and summer months as temperatures rise and rainfall reaches a minimum. However, there is evidence that their frequency has increased as a result of changes in land and water use and also climate change.
Between 2000 and 2009 the frequency of dust storms increased by 70 to 170% in the western provinces, when compared with the preceding 30 years. This increase coincided with a general fall in rainfall and a significant increase in average temperatures.
Iranian scientists have predicted that the country faces a 2 degree C increase in temperatures in the next 25 years with a 9 percent drop in precipitation.
Such conditions would further dry out the soil creating more loose dust and sand.
Increasing population and agricultural demand mean that the water table is falling in many areas which may exacerbate the problem.