|
by PBS.org
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 targeted 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.
Asthma isn't the only disease to worry
about. Rising temperatures may contribute to the emergence of
other deadly diseases. In the Northern Hemisphere, tropical
ailments could spread north while illnesses once common only in summer
could become year-round afflictions. Extreme weather events like
flooding could lead to increased occurrences of cholera, while warmer,
more humid climates could also encourage the growth of toxic molds and
fungi.
Return to
Table of Contents
|
