What was done
The authors studied the long-range transport of viable microorganisms from Africa to parts of the Americas via daily collections of airborne materials captured on aerosol filters throughout 1996-1997 at the top of a 17-m-high tower on a 30-m-high bluff on the easternmost coast of Barbados. In addition to identifying and quantifying the amounts of the different materials they collected, they cultured many of the microorganisms; and they employed a variety of techniques to determine where the captured materials had originated, including satellite monitoring and the calculation of back-trajectories from standard meteorological data.

What was learned
Prospero et al.'s work revealed, in their words, that "significant concentrations of viable (colony-forming) bacteria and fungi are routinely transported with African dust across the Atlantic during much of the year," but that "air masses from the North Atlantic, North America, and Europe yielded no cultivable organisms." In addition, they report that dust concentrations over Barbados increased by about a factor of four between the relatively wet decade of the 1950s and the relatively arid decade of the 1980s, and they say that future changes in climate might therefore "lead to large changes in the concentrations of dust and viable microorganisms over a large area of the western Atlantic, Caribbean, and the eastern US." Although they did not attempt to identify pathogenic microorganisms, Prospero et al. say that some that are harmful to humans, animals and plants could well be transported in this way and that there is therefore "cause for concern," because "it has been demonstrated that readily detectable concentrations of African dust are carried to the southeastern US (Prospero, 1999; Prospero et al., 2001) and over a large area of the US east of the Mississippi as far north as the New England states."

What it means
With respect to Prospero et al.'s conclusion that future changes in climate could alter the magnitude of dust and viable microorganisms transported from Africa to the Americas, we note that over the past quarter-century, when climate alarmists claim that the earth experienced unprecedented increases in both air temperature and CO2 concentration, the findings of Herrmann et al. (2005), plus those of others they cite, indicate there was a great "greening of the Sahel," with rainfall increasing over much of this arid region of Africa and its biomass production exhibiting a strong upward trend that was greater than what would normally have been expected from the observed increase in rainfall, possibly due to a concomitant CO2-induced increase in plant water use efficiency. Hence, it would appear that the pair of environmental changes most abhorred by climate alarmists (rising air temperatures and CO2 concentrations) could well be helping to reduce this major health concern for people living in the "drop zone" of African dust and microorganisms by promoting the development of a much-needed soil-stabilizing vegetative ground cover in many of the dust-source regions.

References
Herrmann, S.M., Anyamba, A. and Tucker, C.J. 2005. Recent trends in vegetation dynamics in the African Sahel and their relationship to climate. Global Environmental Change 15: 394-404.

Prospero, J.M. 1999. Long-term measurements of the transport of African mineral dust to the Southeastern United States: implications for regional air quality. Journal of Geophysical Research 104: 15,1917-15,927.

Prospero, J.M., Olmez, I. and Ames, M. 2001. Al and Fe in PM 2.5 and PM 10 suspended particles in South Central Florida: the impact of the long range transport of African mineral dust. Journal of Water, Air and Soil Pollution 125: 291-317.