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Can we delay a greenhouse warming?
ENVIRON IMPACT ASSESS REV 1986:6;95-98
95
BOOK REVIEW
Changing Climate Carbon Dioxide Assessment Committee, US National Research Council National Academy Press, Washington, DC, 1983
Can We Delay a Greenhouse Warming? Stephen Seidel and Dale Keyes US Environmental Protection Agency, Washington, DC, 1983
Revie,---d by S H E R W O O D B. I O S O Research Physicist, U.S. Water Conservation Laboratory, Phoenix, Arizona
If there is such a thing as an ecological dilemma of our time, the CO2-climate controversy must surely be a leading candidate for that distinction, for the socalled "greenhouse effect" of carbon dioxide is a phenomenon which is truly global in extent and impact. Born of the very basis of the Industrial Revolution, the problem owes its origin to the vast quantities of carbon dioxide (CO2) released to the atmosphere by the burning of fossil fuels such as coal, gas, and oil. The preindustrial concentration of this trace gas of Earth's atmosphere was somewhere in the range of 260 to 270 parts per million (ppm). Now, its concentration is about 350 ppm (Wigley 1983). The report of the National Research Council (NRC) reviewed here projects that a nominally doubled value of 600 ppm probably will be reached by the year 2065. What will be the environmental impact of this phenomenon? That is the primary question posed by the reports of both the NRC and the Environmental Protection Agency (EPA). Both of them provide very similar answers. Both reports predict that a 300- to 600-ppm doubling of the atmospheric CO2 concentration will lead to a 3 _+ 1.5°C increase in mean global air temperature. A warming of this magnitude is almost unprecedented in Earth's recent history. Even more alarming is the suggestion found in both reports that the warming in polar regions will be several times greater. As a consequence, the reports predict that huge amounts of ice will melt, leading to a significant rise in sea level and the flooding of large tracts of coastal lowlands. Rainfall too is expected to be perturbed, with precipitation reductions of about ten percent forecast for key food-producing countries in middle latitudes. As a © 1986 Elsevier Science Publishing Co.. Inc. 52 Vanderbilt Avenue. New York. NY 10017
0195-9255/86/$3.50
96
BOOK REVIEWS
result, the NRC report projects reductions in streamflow for these regions ranging from 40 to 75 percent. The EPA report claims that "agricultural conditions will be significantly altered, environmental and economic systems potentially disrupted, and political institutions stressed." Given such hard-hitting conclusions, one would think that the reports were well founded in experimental science or empirical observation, but such is not the case. Apart from the fact that atmospheric CO2 is known to be on the rise, practically everything else in the two reports is little more than glorified speculation. For instance, the central thesis of a significant global warming rests only on the results of theoretical model calculations. My recent book on this subject, Carbon Dioxide: Friend or Foe? (Idso 1982) documents that many important real-world processes are not adequately incorporated in the climate models employed by the NRC and EPA. It is not surprising that much of what they predict appears to be contrary to what is observed in nature. For example, the data in the NRC report suggest that, based on its climate models, the northern third of the globe should have experienced a CO2-induced wanning of about 3°C between 1880 and 1980. However, the actual temperature history of this region, as found in the NRC report, shows a net warming over this period of only 0.3°C. This order-of-magnitude discrepancy is exactly what I predicted would be found several years ago on the basis of empirical observations of climatic sensitivity (Idso 1980). A second example comes from the satellite snow cover study of Dewey and Heim (1982). Those investigators found that Northern Hemispheric seasonal snow cover increased by 3,000,000 square kilometers between 1966 and 1980--a period when atmospheric CO2 was rising more rapidly than at any prior time-and that this increase in snow cover was accompanied by trends towards earlier accumulation of snow in the fall and later ablation in the spring. Despite these findings, the NRC report still clings to the notion that more CO2 will decrease snow cover as "snowmelt arrives earlier and snowfall begins later." A third example of completely unreal conclusions being derived from a faulty methodology is provided by the NRC report's analysis of streamflow consequences of atmospheric CO2 enrichment. Based upon the assumption that evapotranspiration is controlled "solely by temperature," the NRC report predicts streamflow reductions of 40 to 75 percent for a COz concentration doubling. However, the tendency for atmospheric CO2 enrichment to induce plants to partially close their stomates and thereby reduce their evaporative water loss is even more important. When Aston (1984) included this latter effect in a more realistic model of watershed runoff, he found that "we can expect streamflow to increase from 40 to 90 percent as a consequence of doubling the atmospheric COz concentration." It is evident that there is no basis in fact for any of the adverse climatic
BOOKREVIEWS
97
consequences predicted by the NRC and EPA. However, there are still a number of nonclimatic impacts of atmospheric CO2 enrichment that are significant for the biosphere. For instance, CO2 is one of the primary raw materials of the photosynthetic process; and in a review of 770 prior experimental observations related to this phenomenon, Kimball (1983) concluded that crop yields the world over "probably will increase by 33 percent with a doubling of atmospheric CO2 concentration." Similarly, Kimball and Idso (1983) concluded from a review of the antitranspirant properties of CO2 that % doubling of CO2 concentration could reduce transpiration by 34 percent." As these two effects occur in unison, plant water use efficiency, or the yield produced per unit of water used, will actually double for a doubling of the atmospheric CO2 content. Furthermore, recent research by Rogers et al. (1983) suggests that a quadrupling of the atmospheric CO2 content will lead to a fourfold increase in plant water use efficiency--for both agronomic and forest species. This phenomenal increase in plant water use efficiency will lead to the production of significantly more food with significantly less water in the years ahead. Both rainfall and irrigated agriculture will profit thereby, and much marginal land currently unsuited for cultivation will be put to the plow. The unmanaged biosphere will also benefit, as grasses acquire the ability to successfully grow and reproduce in desert regions and forests begin to migrate out onto the prairies. Indeed, the whole face of the land will be literally transformed in a great greening of the planet. It is hard to see why the rising concentration of atmospheric CO2 has been condemned as it is in the NRC and EPA reports. More CO2 should be good for the world. It should be welcomed as the blessing which decades of sound agronomic research have shown it to be.
REFERENCES
Aston, A. R. 1984. The effect of doubling atmospheric C O 2 o n streamflow: A simulation. Journal of Hydrology 67:273-280. Dewey, K. F. and R. Heim, Jr. 1982. A digital archive of Northern Hemisphere snow cover, November 1966 through December 1980. Bulletin of the American Meteorological Society 63:1132-1141. ldso, S. B. 1980. The climatological significance of a doubling of Earth's atmospheric carbon dioxide concentration. Science 207:1462-1463. ldso, S. B. 1982. Carbon Dioxide: Friend or Foe? An Inquiry into the Climatic and Agricultural Consequences of the Rapidly Rising C02 Content of Earth's Atmosphere. Tempe, Ariz: lBR Press. Kimball, B. A. 1983. Carbon dioxide and agricultural yield: An assemblage and analysis of 770 prior observations. WCL Rept. 14. Phoenix, Ariz: US Water Conservation Laboratory.
98
BOOK REVIEWS
Kimball, B. A. and S. B. ldso. 1983. Increasing atmospheric CO2: Effects on crop yield, water use and climate. Agricultural Water Management 7:55-72. Rogers, H. H., J. F. Thomas and G. E. Bingham. 1983. Response of agronomic and forest species to elevated atmospheric carbon dioxide. Science 220:428--429. Wigley, T. M. L. 1983. The pre-industrial carbon dioxide level. Climatic Change 5:315-320.
95
BOOK REVIEW
Changing Climate Carbon Dioxide Assessment Committee, US National Research Council National Academy Press, Washington, DC, 1983
Can We Delay a Greenhouse Warming? Stephen Seidel and Dale Keyes US Environmental Protection Agency, Washington, DC, 1983
Revie,---d by S H E R W O O D B. I O S O Research Physicist, U.S. Water Conservation Laboratory, Phoenix, Arizona
If there is such a thing as an ecological dilemma of our time, the CO2-climate controversy must surely be a leading candidate for that distinction, for the socalled "greenhouse effect" of carbon dioxide is a phenomenon which is truly global in extent and impact. Born of the very basis of the Industrial Revolution, the problem owes its origin to the vast quantities of carbon dioxide (CO2) released to the atmosphere by the burning of fossil fuels such as coal, gas, and oil. The preindustrial concentration of this trace gas of Earth's atmosphere was somewhere in the range of 260 to 270 parts per million (ppm). Now, its concentration is about 350 ppm (Wigley 1983). The report of the National Research Council (NRC) reviewed here projects that a nominally doubled value of 600 ppm probably will be reached by the year 2065. What will be the environmental impact of this phenomenon? That is the primary question posed by the reports of both the NRC and the Environmental Protection Agency (EPA). Both of them provide very similar answers. Both reports predict that a 300- to 600-ppm doubling of the atmospheric CO2 concentration will lead to a 3 _+ 1.5°C increase in mean global air temperature. A warming of this magnitude is almost unprecedented in Earth's recent history. Even more alarming is the suggestion found in both reports that the warming in polar regions will be several times greater. As a consequence, the reports predict that huge amounts of ice will melt, leading to a significant rise in sea level and the flooding of large tracts of coastal lowlands. Rainfall too is expected to be perturbed, with precipitation reductions of about ten percent forecast for key food-producing countries in middle latitudes. As a © 1986 Elsevier Science Publishing Co.. Inc. 52 Vanderbilt Avenue. New York. NY 10017
0195-9255/86/$3.50
96
BOOK REVIEWS
result, the NRC report projects reductions in streamflow for these regions ranging from 40 to 75 percent. The EPA report claims that "agricultural conditions will be significantly altered, environmental and economic systems potentially disrupted, and political institutions stressed." Given such hard-hitting conclusions, one would think that the reports were well founded in experimental science or empirical observation, but such is not the case. Apart from the fact that atmospheric CO2 is known to be on the rise, practically everything else in the two reports is little more than glorified speculation. For instance, the central thesis of a significant global warming rests only on the results of theoretical model calculations. My recent book on this subject, Carbon Dioxide: Friend or Foe? (Idso 1982) documents that many important real-world processes are not adequately incorporated in the climate models employed by the NRC and EPA. It is not surprising that much of what they predict appears to be contrary to what is observed in nature. For example, the data in the NRC report suggest that, based on its climate models, the northern third of the globe should have experienced a CO2-induced wanning of about 3°C between 1880 and 1980. However, the actual temperature history of this region, as found in the NRC report, shows a net warming over this period of only 0.3°C. This order-of-magnitude discrepancy is exactly what I predicted would be found several years ago on the basis of empirical observations of climatic sensitivity (Idso 1980). A second example comes from the satellite snow cover study of Dewey and Heim (1982). Those investigators found that Northern Hemispheric seasonal snow cover increased by 3,000,000 square kilometers between 1966 and 1980--a period when atmospheric CO2 was rising more rapidly than at any prior time-and that this increase in snow cover was accompanied by trends towards earlier accumulation of snow in the fall and later ablation in the spring. Despite these findings, the NRC report still clings to the notion that more CO2 will decrease snow cover as "snowmelt arrives earlier and snowfall begins later." A third example of completely unreal conclusions being derived from a faulty methodology is provided by the NRC report's analysis of streamflow consequences of atmospheric CO2 enrichment. Based upon the assumption that evapotranspiration is controlled "solely by temperature," the NRC report predicts streamflow reductions of 40 to 75 percent for a COz concentration doubling. However, the tendency for atmospheric CO2 enrichment to induce plants to partially close their stomates and thereby reduce their evaporative water loss is even more important. When Aston (1984) included this latter effect in a more realistic model of watershed runoff, he found that "we can expect streamflow to increase from 40 to 90 percent as a consequence of doubling the atmospheric COz concentration." It is evident that there is no basis in fact for any of the adverse climatic
BOOKREVIEWS
97
consequences predicted by the NRC and EPA. However, there are still a number of nonclimatic impacts of atmospheric CO2 enrichment that are significant for the biosphere. For instance, CO2 is one of the primary raw materials of the photosynthetic process; and in a review of 770 prior experimental observations related to this phenomenon, Kimball (1983) concluded that crop yields the world over "probably will increase by 33 percent with a doubling of atmospheric CO2 concentration." Similarly, Kimball and Idso (1983) concluded from a review of the antitranspirant properties of CO2 that % doubling of CO2 concentration could reduce transpiration by 34 percent." As these two effects occur in unison, plant water use efficiency, or the yield produced per unit of water used, will actually double for a doubling of the atmospheric CO2 content. Furthermore, recent research by Rogers et al. (1983) suggests that a quadrupling of the atmospheric CO2 content will lead to a fourfold increase in plant water use efficiency--for both agronomic and forest species. This phenomenal increase in plant water use efficiency will lead to the production of significantly more food with significantly less water in the years ahead. Both rainfall and irrigated agriculture will profit thereby, and much marginal land currently unsuited for cultivation will be put to the plow. The unmanaged biosphere will also benefit, as grasses acquire the ability to successfully grow and reproduce in desert regions and forests begin to migrate out onto the prairies. Indeed, the whole face of the land will be literally transformed in a great greening of the planet. It is hard to see why the rising concentration of atmospheric CO2 has been condemned as it is in the NRC and EPA reports. More CO2 should be good for the world. It should be welcomed as the blessing which decades of sound agronomic research have shown it to be.
REFERENCES
Aston, A. R. 1984. The effect of doubling atmospheric C O 2 o n streamflow: A simulation. Journal of Hydrology 67:273-280. Dewey, K. F. and R. Heim, Jr. 1982. A digital archive of Northern Hemisphere snow cover, November 1966 through December 1980. Bulletin of the American Meteorological Society 63:1132-1141. ldso, S. B. 1980. The climatological significance of a doubling of Earth's atmospheric carbon dioxide concentration. Science 207:1462-1463. ldso, S. B. 1982. Carbon Dioxide: Friend or Foe? An Inquiry into the Climatic and Agricultural Consequences of the Rapidly Rising C02 Content of Earth's Atmosphere. Tempe, Ariz: lBR Press. Kimball, B. A. 1983. Carbon dioxide and agricultural yield: An assemblage and analysis of 770 prior observations. WCL Rept. 14. Phoenix, Ariz: US Water Conservation Laboratory.
98
BOOK REVIEWS
Kimball, B. A. and S. B. ldso. 1983. Increasing atmospheric CO2: Effects on crop yield, water use and climate. Agricultural Water Management 7:55-72. Rogers, H. H., J. F. Thomas and G. E. Bingham. 1983. Response of agronomic and forest species to elevated atmospheric carbon dioxide. Science 220:428--429. Wigley, T. M. L. 1983. The pre-industrial carbon dioxide level. Climatic Change 5:315-320.