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Aerosols (Non-Biological -- Natural) -- Summary
Dust is about as natural and ubiquitous a substance as there is.  Hence, one would think we would have a pretty good handle on what it does to earth's climate as it is moved about by the planet's ever-active atmosphere.  But, alas, such is not the case, as was made strikingly clear by Sokolik (1999), who with the help of nine colleagues summarized the sentiments of a number of scientists who have devoted their lives to studying the subject.

The Sokolik-led report notes that state-of-the-art climate models "rely heavily on oversimplified parameterizations" of many important dust-related phenomena, "while ignoring others."  As a result, the group concludes that "the magnitude and even the sign of dust net direct radiative forcing of climate remains unclear."  Now that's uncertainty.  In addition, they say that "a challenge remains in relating dust climatology and the processes controlling the evolution of dust at all relevant spatial/temporal scales needed for chemistry and climate models."  Once again, therefore, man is truly humbled by the complexity of nature; but to talk to a climate alarmist, one would never know it.

In addition to impacting the field of climate change, airborne mineral dust - or, more properly, the biological entities that often hitch a ride on it - may have significant implications for the health of earth's coral reefs.  In a study of the "hundreds of millions of tons/year of soil dust that have been crossing the Atlantic during the last 25 years," for example, Shinn et al. (2000) make a good case for the proposition that the influx of dust of African origin to the western Atlantic has been partially to blame for much of the declining health of Caribbean corals, including that generally attributed to heat-induced bleaching, over the past quarter century.  They make this attribution on the basis of the facts that (1) the soil fungus Aspergillus sydowii, which is the cause of Caribbean-wide sea fan disease, has been cultured from air samples taken during dustfalls in the Virgin Island, but that spores of the fungus are absent when the air is clear, plus the fact that (2) Caribbean-wide mortalities of acroporid corals and coral bleaching beginning in 1987 correlate with years of maximum African dust flux into the Caribbean.

Clearly, much more work must be done in both of these important areas, i.e., the climatic and biological implications of airborne dust, for the answers to many vexing questions may well be truly blowin' in the wind.

References
Shinn, E.A., Smith, G.W., Prospero, J.M., Betzer, P., Hayes, M.L., Garrison, V. and Barber, R.T.  2000.  African dust and the demise of Caribbean coral reefs.  Geophysical Research Letters 27: 3029-3032.

Sokolik, I.N.  1999.  Challenges add up in quantifying radiative impact of mineral dust.  EOS: Transactions, American Geophysical Union 80: 578.