Published online 17 February 2004 | Nature | doi:10.1038/news040216-6

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Are greenhouse gases drying Africa's dust bowl?

US citizens choking on African dust may have themselves to blame.

Huge dust storms blow from west Africa across the Atlantic.Huge dust storms blow from west Africa across the Atlantic.© NASA

In Miami, traffic fumes aren't the only thing choking the air. Several times each summer, health standards are breached because of dust blowing across the ocean from Africa.

Local politicians might be tempted to point the finger of blame at African land-use practices. But they should perhaps look closer to home, atmospheric scientist Joseph Prospero of the University of Miami told the American Association for the Advancement of Science meeting in Seattle.

Since 1965, air gusting across the Atlantic on trade winds has been sampled at stations in Miami, Bermuda and Barbados. In the summer, the air at these sites can contain so much dust that it exceeds health standards for particulates - which can be dangerous for those with respiratory or heart disease.

Prospero has found that there is a strong correlation between the amount of dust blowing into the Caribbean and drought in the Sahel region, south of the Sahara Desert. More dust turns up at his sampling stations following years with little rainfall1.

Rainfall records for the past century show that the Sahel is suffering a prolonged drought that began some three decades ago. This coincides with the period during which the global warming trend has become most obvious, Prospero told the AAAS.

The discovery suggests that Africa's dust bowl may be a consequence of greenhouse gas emissions, which come largely from the United States and other developed countries.

If so, then any suggestion that Africa is to blame for the respiratory problems of US citizens should be turned on its head, Prospero suggests. He is now seeking funds for expeditions to study some of the main sources of the dust, including the Bodele depression in northern Chad.

Prospero and other experts say that they must also turn their attention to the health impacts of dust in Africa. "Local pollution that becomes international pollution is always much worse locally," says atmospheric chemist Sherwood Rowland of the University of California at Irvine. "If it's our fault, how do we address the issue of health impacts in Africa where dust concentrations are much, much higher?" asks Prospero. 

  • References

    1. Prospero, J. M. & Lamb, A.B. African droughts and dust transport to the Caribbean: climate change implications. Science, 302, 1024 - 1027, (2003).  | Article | ISI | ChemPort |