Michele Monteil studying a patient.

Just over the course of her own lifetime, physician Michele Monteil has found an alarming rise of childhood asthma in her native Trinidad. Levels of asthma here are among the highest in the world. The incidence of asthma on Barbados and nearby Trinidad, as documented by the Caribbean Allergy and Respiratory Association (CARA), has increased 17-fold since 1973.

Concurrently, marine biologist Ginger Garrison has noted an increasing incidence of sea fan disease in the tropical waters around the Caribbean. Could these two disparate events be connected? Independently, these researchers have linked their target ailments to a surprising single suspect – African dust.

Every year, several hundred million tons of African dust are transported across the Atlantic to the Caribbean, Central and South America. Summer storms can lift dust as high as 15,000 feet over the African deserts and then out across the Atlantic. Garrison and her colleagues discovered that a toxic fungal pathogen known as Aspergillus sydowii was traveling in this African dust and could be a main culprit behind sea fan diseases.

Ginger Garrison studying a sea fan.

It appears episodic dust storms are capable of depositing disease-ridden particles across the Caribbean. These particles are carried in persistent trade winds blowing across the Atlantic from the Sahara Desert and bordering drought-ridden areas such as Lake Chad. Climatologist Jim Hurrell has discovered that the strength of these tradewinds is, in part, attributable to a remarkable feature of the atmosphere that sits over the north Atlantic: two gigantic air masses, one high pressure, the other low-known as the North Atlantic Oscillation (NAO). (Some scientists refer to the NAO as the Arctic Oscillation or alternatively the North Annular Oscillation.)

The two air masses of the NAO propel storms up into the northern regions of Europe and Eurasia while simultaneously shuttling dust from Africa over to the Americas. During the 1980s and the 1990s, these two air systems tended to be locked in an intense positive phase one winter after the next. This pattern has persisted for the last 20-30 years.

Modeling this phenomenon, Hurrell discovered that Earth's rising temperature is affecting the year-to-year behavior of this massive atmospheric system. Focusing on an area of the world where the average temperature has been rising particularly fast — the Indian Ocean — Hurrell's models suggest that the energy released into the atmosphere by the warming waters there may be reinforcing the energy of the North Atlantic Oscillation.

Related Links
»	Learn more about how African dust clouds are associated with increased pediatric asthma accident and emergency admissions on the Caribbean island of Trinidad.
»	For details on coral mortality, the African dust hypothesis and health visit the USGS website.

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