Of the carbon contained in the CO2 that is emitted to the atmosphere by the activities of man, some remains in the air, some enters the world's oceans, and some is absorbed on land. The equation is not perfectly balanced, however, for less remains in the atmosphere than what is predicted on the basis of current ideas about the strength of oceanic and terrestrial carbon sinks. Hence, there must be an additional carbon sink that accounts for this "missing carbon," and the search for its identity is an ongoing scientific challenge.
It has long been our view - and that of our father (Idso, 1986, 1991a,b, 1995) - that the missing carbon sink is but an unrecognized part of the well-known terrestrial carbon sink, the common underestimation of which is due to the fact that the aerial fertilization effect of atmospheric CO2 enrichment is simply bigger than what many people have been willing to believe. New data, however, are beginning to open their eyes to the tremendous power of the terrestrial biosphere to capture and sequester carbon.
Two of the most influential papers in reformulating the world's thinking on the subject were published in a single issue of Science. In the first report, Phillips et al. (1998) described how tropical forests in Central and South America alone are yearly sequestering enough carbon to account for fully 40% of the global missing carbon sink. The second report was even more astounding. On the basis of atmospheric and oceanic CO2 data, Fan et al. (1998) calculated that between the latitudes of 15 and 51°N, the North American land mass is yearly sequestering, in the words of Science news writer Jocelyn Kaiser (1998), "a whopping 1.7 petagrams of carbon a year - enough to suck up every ton of carbon discharged annually by fossil fuel burning in Canada and the United States."
In the same year, Lutze and Gifford (1998) published a report that shed even more light on the subject. They grew swards of a C3 grass for four years in microcosms maintained at 360 and 720 ppm CO2 and three levels (low, medium, high) of soil nitrogen content, finding CO2-induced increases in final soil carbon content of 4, 9 and 17%, respectively. The authors concluded that if all terrestrial ecosystems responded to elevated CO2 in a similar way, this phenomenon would account for all of the "missing carbon" of the entire world.
These several observations from diverse fields of science are welcome news for those who worry about potential CO2-induced global warming. They indicate that the seeds of a solution are inherent in the original phenomenon of concern, namely, the ongoing rise in the air's CO2 content, which exerts a negative feedback on its own progression via its stimulation of plant productivity.
References
Fan, S., Gloor, M., Mahlman, J., Pacala, S., Sarmiento, J., Takahashi, T. and Tans, P. 1998. A large terrestrial carbon sink in North America implied by atmospheric and oceanic carbon dioxide data and models. Science 282: 442-446.
Idso, S.B. 1986. Industrial age leading to the greening of the Earth? Nature 320: 22.
Idso, S.B. 1991a. The aerial fertilization effect of CO2 and its implications for global carbon cycling and maximum greenhouse warming. Bulletin of the American Meteorological Society 72: 962-965.
Idso S.B. 1991b. Reply to comments of L.D. Danny Harvey, Bert Bolin, and P. Lehmann. Bulletin of the American Meteorological Society 72: 1910-1914.
Idso, S.B. 1995. CO2 and the Biosphere: The Incredible Legacy of the Industrial Revolution. Department of Soil, Water & Climate, University of Minnesota, St. Paul, MN.
Kaiser, J. 1998. Possibly vast greenhouse gas sponge ignites controversy. Science 282: 386-387.
Lutze, J.L. and Gifford, R.M. 1998. Carbon accumulation, distribution and water use of Danthonia richardsonii swards in response to CO2 and nitrogen supply over four years of growth. Global Change Biology 4: 851-861.
Phillips, O.L., Malhi, Y., Higuchi, N., Laurance, W.F., Nunez, P.V., Vasquez, R.M., Laurance, S.G., Ferreira, L.V., Stern, M., Brown, S. and Grace, J. 1998. Changes in the carbon balance of tropical forests: Evidence from long-term plots. Science 282: 439-442.