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The Climatological Challenge of Airborne Dust
Volume 3, Number 2: 15 January 2000

In our previous editorial (Vol. 3, No. 1: Questions, Questions, Questions ...), we illustrated the paucity of our knowledge of the intricacies of the many different ways by which clouds may (or may not) influence climate, particularly within the context of rising atmospheric CO2 concentrations.  We now indicate the degree to which another airborne substance falls within this same category of limited understanding: atmospheric dust.

Our source of information for this brief review is the report of Sokolik (1999) - produced with the help of G. Bergametti, G. Carmichael, D. Gillette, L. Gomes, Y. Kaufman, J. Penner, L. Schuetz, W. Von Hoyningen-Huene and D. Winkler - which summarizes the sentiments of a number of scientists who have devoted their lives to studying the subject, as presented at an international workshop on mineral dust that was held in Boulder, Colorado, June 9-11, 1999.

The report begins by noting that state-of-the-art climate model predictions "rely heavily on oversimplified parameterizations" of many important dust-related phenomena, "while ignoring others."  As a result, the reporting group states that "the magnitude and even the sign [our italics] of dust net direct radiative forcing of climate remains unclear."

Now that's uncertainty!  And how can one make policy about future climate change when the impacts of changes in potentially important elements of the present climate cannot be ascertained, even qualitatively?

So what are some of the questions scientists have about airborne dust?  The contributors to the Sokolik report name several: (1) How does one quantify dust emission rates from both natural and anthropogenic (disturbed) sources with required levels of temporal and spatial resolution?  (2) How does one accurately determine the composition, size and shape of dust particles from ground-based and aircraft measurements?  (3) How does one adequately measure and model light absorption by mineral particles?  (4) How does one link the ever-evolving optical, chemical and physical properties of dust to its life cycle in the air?  (5) How does one model complex multi-layered aerosol stratification in the dust-laden atmosphere?  (6) How does one quantify airborne dust properties from satellite observations?

The report makes some interesting observations in discussing these questions.  It notes, for example, that (1) what is currently known (or believed to be known) about dust emissions "is largely from micro-scale experiments and theoretical studies," (2) new global data sets are needed to provide "missing information" on input parameters (such as soil type, surface roughness and soil moisture) required to model dust emission rates, (3) improvements in methods used to determine some of these parameters are also "sorely needed," (4) how to adequately measure light absorption by mineral particles is still an "outstanding problem," and (5) it "remains unknown how well these measurements represent the light absorption by aerosol particles suspended in the atmosphere."

In light of these problems, it is readily understandable why the report claims 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."  And until this challenge is met, we will but "see through a glass, darkly."  Even Al Gore - who was recently described by RFK Jr. as humanity's "last best chance to save the planet" (Webster, 1999) - cannot give us the answers we need; for the presidential hopeful has been quoted by Sobieraj (1999) as stating, relative to a question about what the future might bring, that "nobody has a crystal ball," even in regard to what he himself might someday do about a matter of almost infinitely less complexity.  (Well, maybe the tax code isn't all that simple; but you get the point.)

Clearly, there is no easy, magical way to determine the full scope of the workings of the many interrelated components of earth's incredibly complex climate system.  Each and every bit of knowledge gained must be pried - sometimes delicately, sometimes by dint of brute force - from the matrix of ignorance to which we are hostage, until we have paid the price, by painstaking and plodding research, to obtain the many keys required to unlock the host of doors behind which lie the answers to the myriad sub-questions that must all be answered in order to approach, with any hope of success, the great dilemma that confronts us.

And mind you, children are not born with this knowledge; the electorate does not bestow it upon presidents.  It must be won by skilled and highly-trained practitioners on the challenging battlefield of scientific investigation; and it will be acquired no faster than we diligently seek it.  Indeed, certain types of such knowledge require entire generations of dedicated pursuit, before they yield their treasures.

May we be so humble as to realize that we are but paupers in our current understanding of things climatic, and resist those restive forces that would incite us to act upon that which is as yet so tenuous, that as a vapor, it may well melt quietly away before our very eyes, when exposed to the illuminating rays of the more substantial understanding that will surely result from our further diligent efforts to uncover the truth about how the complete and integrated climate system of Planet Earth really works.

Dr. Craig D. Idso
Dr. Keith E. Idso
Vice President

Sobieraj, S.  1999.  Gore refuses to rule out tax increases.  The Tribune (Thomson Newspapers Inc.) 51 (339): A17.

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

Webster, G.  1999.  Environment is focus of RFK Jr.'s valley talk.  The Tribune (Thomson Newspapers Inc.) 51 (339): A10.