Our response (Perspective No. 2) was that a potential increase in pollen-induced allergies was but a small price to pay for the concomitant CO2-induced increase in agricultural production that is desperately needed to provide the food required to avoid the starvation of untold millions of people a mere couple of decades down the road; and we thus suggested that we let the historical and still-ongoing rise in the air's CO2 content run its natural course.  In this editorial, we present yet a third view of the issue (Perspective No. 3) that provides even more support for our position.

We take as the text for our sermon the recent paper of Prospero (2001), who is a world authority on airborne dust.  The eminent scientist - who is a professor in the Division of Marine and Atmospheric Chemistry at the Rosenstiel School of Marine and Atmospheric Science, as well as director of the Cooperative Institute of Marine and Atmospheric Studies - begins his review of the subject by noting that large quantities of dust can be carried great distances across both the Atlantic and Pacific Oceans.  From Africa, for example, he informs us that periodic dust storms carry great burdens of soil-derived particulates "eastward across the Middle East and the Arabian Sea, north over the Mediterranean to Europe, and west across the tropical Atlantic to North and South America."  Likewise, he notes that "every spring, frontal storms emerging from Siberia generate large quantities of dust in China," some of which weather disturbances "move eastward over the North Pacific and across the northern United States and Canada," until they finally dissipate and drop the remainder of their dust load over the North Atlantic.

Because this dust is carried such long distances, what remains when it reaches the Americas is usually of very small size.  In fact, about half of the dust particles are small enough to be deeply inhaled.  Furthermore, says Prospero, "the dust particles are heavily coated with iron," such that "the average iron content of all dust particles from Africa is 3 to 5 percent."  Why is this important?  Because, as he continues, "a substantial fraction of the iron on dust could be quickly released into the lungs once the particles are deposited on lung tissue," and iron, as Prospero notes, is "particularly efficient in producing an inflammatory response in the lungs."

As if this were not enough of a problem, Prospero indicates that substantial numbers of pathogenic fungi, bacteria and viruses capable of infecting humans hitch a ride on the African dust particles and survive the trans-Atlantic trip.  What is more, they fulfill their potential for raising havoc upon their arrival in the Americas.  He notes, for example, that "reports from Caribbean islands show that emergency room visits for asthma and other respiratory illnesses increase markedly during African dust events."  And from the Caribbean islands, the dust goes on to visit - and provide the potential to infect - nearly everyone in the United States living east of the Mississippi River.

So what has all of this to do with CO2?  First of all, on the meteorological side of the coin, if the earth warms as climate models predict it will, there should be a concomitant increase in the planet's hydrologic cycle; and enhanced global precipitation would help to "settle the dust" nearly everywhere on earth, both in source regions and across the long intercontinental and trans-oceanic routes of its aerial transport.  Second - and contrary to the claims of the world's climate alarmists - both the frequency and the intensity of the storms that lift and transport dust would likely decline in a warming world, as indicated by the many pertinent research articles we have reviewed on our website (see, for example, Weather Extremes in our Subject Index).

Then there's the even more important biological aspect of the issue.  A doubling of the air's CO2 content typically leads to increases of anywhere from 20 to 80% in plant growth rates, while it simultaneously reduces plant transpiration rates, so that plant water use efficiency, or biomass production per unit of water transpired, increases even more than plant growth as the atmosphere's CO2 concentration rises.  Hence, with this CO2-conferred ability to produce more biomass with less water, plants of the future will be able to grow and reproduce over large areas of the earth where it has previously been too dry for them to even exist; and these areas are the very regions that serve as the planet's major sources of windblown dust.

Consequently, with greater vegetative cover - in some cases, almost infinitely greater - it will be far more difficult for winds of the future to erode the soils of these regions and spread their constituent particles abroad in the earth, as they do today.  And this reduction in windblown dust, which comes courtesy of the biological benefits of atmospheric CO2 enrichment, should greatly reduce the worldwide incidence of the host of respiratory diseases that result from inhaling iron-coated particles covered with pathogenic fungi, bacteria and viruses, which are considerably more effective in terms of inducing illness than - shall we say - mere pollen.

Clearly, therefore, mandating reductions in anthropogenic CO2 emissions with the stated goal of enhancing human health would not only be an enormous wasted effort; it would actually tend to do just the opposite of what its proponents claim it would, i.e., it would degrade human health.

Reference
Prospero, J.M.  2001.  African dust in America.  Geotimes 46 (11): 24-27.