What was done
Each spring, Asian dust storm (ADS) events originating in the deserts of Mongolia and China transport great quantities of fine particulate matter of 10µm diameter (PM10) to populated cities of East Asia, including Taipei, Taiwan, where the tiny particles have the potential to impact people's lives in a very big way.  In an attempt to assess one aspect of this phenomenon, the authors identified 54 ADS events that affected Taipei from 1996 to 2001; and they evaluated the impacts of these events on hospital admissions for primary intracerebral hemorrhagic stroke (PIH), ischemic stroke (IS), as well as the conglomerate of strokes of all types.

What was learned
Yang et al. found that associations between dust storms and total stroke admissions and PIH and IS admissions were all prominent 3 days after ADS events, with the relative risk for total stroke admissions being 1.05, that for IS admissions being 1.04, and that for PIH admissions being 1.15, the latter of which findings was statistically significant.  For this particular stroke category, they additionally determined that risk of stroke rose by 2.67% for each 10 µg/m³ increase in PM10 concentration above the normal mean value of 55.43 µg/m³.

What it means
How will the ongoing rise in the air's CO2 content impact this phenomenon?  First of all, the well-documented increase in plant water use efficiency that results from increases in atmospheric CO2 concentration should allow more plants to grow in the arid source regions of the Asian dust clouds, which should help to stabilize the soil and decrease its susceptibility to wind erosion, thereby reducing the severity of ADS events.  Second, the propensity for elevated CO2 concentrations to increase moisture contents of soils beneath plant canopies as a consequence of CO2-induced reductions in plant transpiration should also lead to greater ground cover and reduced wind erosion.  Third, the ability of extra CO2 in the atmosphere to enhance the growth of cryptobiotic soil crusts should likewise stabilize the surface of the soil.  And fourth, as noted by Zavaleta et al. (2003), global warming itself may increase soil moisture contents in water-limited regions by hastening plant senescence and thereby reducing the period of time over which transpiration-driven soil water losses occur.  As a result, if the air's CO2 content continues to rise, even in the face of further warming, we should see a gradual reduction in the number of PM10-induced strokes in the populace of Taipei, Taiwan, as well as in other places affected by Asian and other dust storms.

Reference
Zavaleta, E.S., Thomas, B.D., Chiariello, N.R., Asner, G.P., Shaw, M.R. and Field, C.B.  2003.  Plants reverse warming effect on ecosystem water balance.  Proceedings of the National Academy of Science USA 100: 9892-9893.