The four-member team of Russian and American scientists says "there has been a general warming trend in Central Asian republics on the order of 1-2°C since the beginning of the 20th century," but they add that it is expressed most strongly in winter and that "the amplitude of this trend seems to be comparable with Holocene climate variability," suggesting that it is nothing unusual nor does it require an anthropogenic explanation.  Citing the IPCC (2001), on the other hand, they report that precipitation has remained basically unchanged throughout the 20th century, stating that "there were no discernible trends in annual precipitation during 1900-95 for the region as a whole, nor in most parts of this region."

In the face of unchanging precipitation and significant warming, one might expect that the aridity of Central Asia would have increased significantly in recent years, especially throughout the 1990s, when climate alarmists claim the world saw its most oppressive heat of both the 20th century and the past two millennia.  However, Lioubimtseva et al. report that "analyses of the NOAA AVHRR temporal series since the 1980s showed a decrease in aridity from 1991-2000 compared to 1982-1990 in the northern part of the region and a southward shift of the northern boundary of the desert zone in Central Asia," citing the work of Zolotokrylin (2002).

So what's the explanation for this unexpected development?  Lioubimtseva et al. suggest it could well have been the historical rise in the air's CO2 content.

The scientists begin their elucidation of this hypothesis by noting that "an increased atmospheric CO2 concentration has direct and relatively immediate effects on two important physiological processes in plants: it increases the photosynthetic rate, but decreases stomatal opening and therefore the rate at which plants lose water," so that "the combination of these two factors, increased photosynthesis and decreased water loss, implies a significant increase of water [use] efficiency (the ratio of carbon gain per unit water loss) and ... a reduction in the sensitivity to drought stress in desert vegetation as a result of elevated atmospheric CO2," citing the work of Smith et al. (2000) in support of this concept.  As a result, they note that these effects could "increase productivity and biomass of natural desert vegetation," which would, of course, make the land appear (and effectively be) less arid.

Buttressing this reasoning with experimental evidence obtained from the region itself, Lioubimtseva et al. report that "CO2-enrichment experiments (both chamber and free-air) conducted in the Kara Kum (Voznesensky, 1997) and Kyzyl Kum (Voznesensky, 1997; Zelensky, 1977) deserts showed a 2-4 times increase in the photosynthetic rate under the saturating CO2 concentrations," and that "three Kara Kum species (Eminium lehmanii, Rhemum turkestanuikum and Ephedra stobilacea) responded with a six-fold increase in photosynthetic rate (Nechaeva, 1984)."  In addition, they report that "the CO2 fertilization effects included not only higher vegetation but also microphytic communities including mosses, lichens, fungi, algae, and cyanobacteria," which communities, in their words, "form biogenic crusts on the soil surface varying from a few millimeters to several centimeters in thickness and play a significant role in the desert ecosystems controlling such processes as water retention and carbon and nitrogen fixation in soils," as is described more fully in the materials archived under the heading Deserts (Algae and Lichens) in our Subject Index.

In light of these many observations, all we can say is that as bad as climate alarmists claim rising atmospheric CO2 concentrations and temperatures are for earth's biosphere, and especially for its water-stressed deserts and arid regions, the plants that reside there don't seem to be getting the message.  In fact, they appear to be thriving in the face of the double-barreled challenge, which in reality is actually a blessing in disguise.

Sherwood, Keith and Craig Idso

References
Lioubimtseva, E., Cole, R., Adams, J.M. and Kapustin, G.  2005.  Impacts of climate and land-cover changes in arid lands of Central Asia.  Journal of Arid Environments 62: 285-308.

Nechaeva, N.T. (Ed.).  1984.  Resursy biosphery pustin Srednei Azii i Kazakhstana.  Nauka, Moscow, Russia.

Smith, S.D., Huxman, T.E., Zitzer, S.F., Charlet, T.N., Housman, D.C., Coleman, J.S., Fenstermaker, L.K., Seemann, J.R. and Nowak, R.S.  2000.  Elevated CO2 increases productivity and invasive species success in an arid ecosystem.  Nature 408: 79-82.

Voznesensky, V.L.  1977.  Fotosyntez pustinnih rastenij.  Nauka, Leningrad, Russia.

Zelensky, O.B.  1977.  Ecologo-fisiologicheskije aspekti izuchenija fotosinteza.  Nauka, Leningrad, Russia.

Zolotokrylin, A.N.  2002.  The indicator of climate aridity.  Arid Ecosystems 8: 49-57.