- The Washington Times - Wednesday, November 19, 2003

MIAMI — Scientists say dust blowing from the Sahara Desert across the Atlantic Ocean into the Caribbean Sea and Florida has increased in recent decades, with implications for the climate and atmospheric and public health.

The movement of dust from Africa to the West Indies and the southeastern United States has increased since 1970 because of an increase of dry weather in the Saharan region.

The study was conducted for the National Oceanographic and Atmospheric Administration by Joseph M. Prospero of the University of Miami and Peter Lamb of the University of Oklahoma.

Both have been working on the phenomenon for more than 30 years.

Mr. Prospero said more studies are needed, but there is evidence that particles in the atmosphere can affect climate. He said that there is an interaction in the atmosphere between the dust and natural factors and that the particles can have an impact on cloud patterns.

“There is a very complex climate-dust interaction. A number of [research] groups are starting work on it,” Mr. Prospero said.

“The amount of dust transported from Africa could affect South Florida by suppressing rainfall and worsening droughts,” he said.

“Because of the sensitivity of dust emissions to climate, future changes in climate could result in significant changes in emissions from African and other arid regions that, in turn, could lead to impacts in climate over large areas,” Mr. Lamb said.

“These results demonstrate how climate processes can bring about changes in our environment that could have a wide range of consequences on an intercontinental scale,” he added.

A key result of the most recent study is that decreased rainfall in Africa results in a sharp increase of dust moving across the Atlantic the next year.

“The study found that dust concentrations were sharply lower during much of the 20th century before 1970, when rainfall across the Sudano-Sahel region was more normal and when it was especially wet during the 1950s and early 1960s,” Mr. Prospero said.

“Since 1970, the region has suffered varying degrees of drought, which has caused the amount of dust to increase,” he went on.

Work done by Mr. Prospero in past years shows that, in addition to the yearlong transport of dust to the eastern Caribbean, large quantities of dust are carried to the southeastern United States every summer.

The dust often results in a visible summertime haze over southern Florida. The Saharan dust is most prevalent there during the summer, when the trade winds blow in from the east.

Fine particles, which also can have industrial sources, are small enough to be inhaled — a definite health hazard.

Mr. Prospero said the Saharan dust can contribute as much as half of the particles during Miami’s smog season in June, July and August, mild as it is.

Doctors say residents with respiratory problems such as asthma, emphysema or even hay fever could expect worse symptoms, but few are likely to require special treatment.

But they also say that people with those problems should remain indoors during those hazy summer days and cut back on vigorous outdoor activity.

Mr. Prospero said the dust was so thick in Barbados in the 1980s that the air exceeded danger standards set by the Environmental Protection Agency for the United States.

He said the effect on northern Africa is obviously even worse.

“During the dry years, it is horrendous. That’s one of the areas in the world that people don’t pay much attention to,” he said.

Forecasters at the National Hurricane Center in Miami, who make extensive use of satellite photographs, said the dust can be detected in the pictures.

Mr. Prospero said no one has come up with an answer to why there have been more drought conditions in the Sahara in the past 30 years.

“We do know we have the highest dust concentration in the years we have an El Nino,” he said.

El Nino is a warm-water phenomenon that occurs off the Peruvian coast. It produces storms in much of the hemisphere, but cuts down on the number of damaging hurricanes in the Atlantic.

Mr. Prospero said many other conditions could be a factor, including conditions caused by humans. But he is quick to point out there is no concrete evidence pointing to human activity as the culprit.


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