By Sylvan H. Wittwer
I report as one who, 35 years ago, conducted some of the very first experiments in the western world with controlled levels of atmospheric carbon dioxide on the yield and productivity of greenhouse grown food crops (Wittwer andRobb, 1964). The results were dramatic. Many followed after us. Ten years later; news releases began to vigorously report the possible hazards of a global warming., and the "Greenhouse Effect" became a part of our vocabulary. Computer modeling and simulation of climate began to emerge and the popularization of a gloom and doom syndrome.
I have now lived through eight decades of "Global Warming." Levels of atmospheric carbon dioxide have risen from less than 300 ppm to over 360 ppm. During this span, the world's population has increased over three-fold, and food production by an estimated five-fold. Satellite-monitored temperature data are now in, and show that during their entire life span thee has been no global warming that could be ascribed to human activity. The "greenhouse effect" warming is non-existent, irrespective of computer simulations of climate change and reported declarations emanating from the United Nations Intergovernmental Panel on Climate Change (IPCC).
The popular media continues to lead Americans to believe that global environmental changes are heading us to disaster: As recently as February 28, 1997, CNN News announced the United States has been declared the world's worst polluter: This related to the release of carbon dioxide into the atmosphere, thus speeding the rate and magnitude of a global warming. Beneath all of this rhetoric, the evidence is that the rising levels of atmospheric carbon dioxide are very favorable fo rthe most essential of human activities, and oujr most important renewable resource, namely the production of food.
Not many people think of it in this way, but food, climate, and the rising levels of atmospheric carbon dioxide are uniquely interrelated. Food production is a critical and an essential renewable resource. Without food, the human race would not survive. The production of this renewable resource, upon which all life depends, is possible only through photosynthesis, the most important of bichemical processes. An essential raw material, almost always in short supply; is the low level of atmospheric carbon dioxide. For example, an acre of corn crop must process over 40,000 tons of air to produce the record yeild of more than 130 bushels per acre recorded in the United States for 1995.
Globally; some 25 crops stand between people and starvation. The largest single food group is the cereal grains, of which corn is a leading member. They provide approximately 60% of the calories and 50% of the protein consumed by the human race. The legumes provide about 20% of the world's protein. The balance of calories, protein, and essential vitamins and minerals is obtained from tuber and root crops and various fruits, nuts, and vegetables. Food animals, deriving their food either directly or indirectly from plants, provide 20% of the protein with 5% coming from fish.
The most determinant factor in agricultural (food) production is weather or the climate. For agriculture, climate must be managed both as a resource to be used wisely ont he one hand and a hazard to be dealt with on the other. Food production is very much a function of climate, which in itself is unpredictable. In fact, the principal characteristic of climate is variability. Predictive climate changes derived from computer simulations are far from accurate and may be deceptive even with the most advanced modeling. Volcanoes, cloud cover regional characteristics, and changing of atmospheric components currently cannot (and may never) be successfully factored into an accurate climate model.
From the perspective of food security, the stability of agricultural production is an important, if not more so, than the magnitude of output. Climate variability has a greater impact on agricultural productivity--both its magnitude and stability--than does climate change. Extremes in weather, rather than averages, affect agriculture. Both crops and livestock are sensitive to weather over relatively short periods of time. Annual averages of temperature and rainfall do not convey short-term deficiencies, which impact both the volume and stability of food output. History reveals that for food production, warming is better than cooling. In fact, "the silver linine in the growing cloud of atmospheric CO2 that may warm the plane is more raw material for photosynthesis" (Waggoner, 1994).
Of all the natural climate hazards, drought is what farmers fear most. The lack of water is the single greatest impediment to plant growth and global food production. This is illustrated by the fact that today, irrigated cropland--about 17% of the world's total--produces one-third of the agricultural output. For the United States, the 12% of the cultivated farm land that is irrigated, accounts for 37% of crop production. U.S. agriculture consumes, mostly through irrigation, 80 to 85% of the nation's fresh water resources. For the world, it is more than 65%.
The most readily identifiable potential climate impact of significant magnitude on future living standards of the human race is availability of water resources. The efficiency of their use will be a major key to future food security.
We now introduce the impacts of the rising level of atmospheric carbon dioxide. First, we have its presumed effect on climate change, and second, its effect on food production. The climate change impact is characterized by the widely publicized global warming or the so-called "greenhouse effect." Presumably this also is causing an increased frequency of extreme or hazardous events. Conversely, elevated levels of atmospheric carbon dioxide have a decidedly beneficial effect on crop production through an enhancement of photosynthetic capacity and an increase in water-use efficiency. Additionally, hundreds of experiments now show partial alleviation of the harmful effects of both marginally low and high temperatures, air pollutants, a lessening of the environmental hazards imposed by drought, alkalinity, and mineral stresses--both excesses and deficiencies--low-light intensities and UV-B radiation )Idso and Idso, 1994).
Concerning changing levels of atmospheric carbon dioxide, there are some well-known facts. First, there is a documented increase. The isolated test site at Mauna Loa in Hawaii shows more than a 12% increase in the mean annual concentration, from 316 ppm by volume of dry air in 1959 to the 1996 level of 360 ppm . The current annual rate of increase is about 0.5 or 1.6 ppm. Carbon dioxide source-sink models predict that the current level of atmospheric CO2 will be doubled by the latter part of 21st century.
Second, the increase is truly global. The earth's atmosphere is very effective in dispensing emissions from whatever the source, be it natural or man-made.
Third, with the average level oc CO2 rising, there is an annual oscillation of the earth's atmospheric CO2. The CO2 level begins to fall in the spring and continues through the summer months as it appears to be sequestered by the vegetation of the Northern Hemisphere. In the late autumn, there is a resurgence of CO2 into the atmosphere. This results in new heights by mid-winter. With the amplitude increasing by about 0,5% each year, it appears the concentration or amount of the earth's biomass is either increasing or is steady. It is not decreasing.
This there are two ongoing global experiments inadvertently being conducted by the world's people. The outcomes of either we do not know. First is the so-called global warming resulting from increasing amounts of atmospheric CO2 and other radiatively active trace gases. Second is the effect of the enrichment on improved photosynthetic capacity, and its effects on plant growth and development. This in turn, increases food production, forestry output, and biological productivity with an improvement in water-use efficiency.
Meanwhile, these two experiments will likely continue well into the 21st century with the final results not fully realized. The topics of food security, the magnitude of climate change (global warming), and the beneficial biological effects of rising levels of atmospheric carbon dioxide are rent with both political and scientific controversy. There are those, including the U.S. Congress and the president, who are still advocating immediate action with accompanying costs of billions of dollars for reducing the world's output of CO2. Global initiatives concerning such wer promoted at the Rio Earth Summit in 1992, and again in the recent Berlin Assembly in March 1995. These are not warranted. Global satellite readings of temperatures over the earth show there has been no warming.
To date, our knowledge of the climate effects of the rising CO2 and other greenhouse gases in the atmosphere is inadequate for initiating any global attempt to change the climate. If the climate does change, some warming could be tolerated, and may even be beneficial with no reductions in food production. A warming trend would increase the lengths of the growing seasons, encourage farmer adaptations, and favor the introduction of new technologies and cultural practices. The results would be crops and food animals more resistant to environmental stresses. The prospects of climate change from increasing levels of atmospheric carbon dioxide do not frighten many agriculturists, farmers or foresters. There are many disparities among interests of farmers and other segments of our society. A rainfall of two or more inches in 24 hours may be newsworthy as an extreme or hazardous climatic event for politicians, environmentalists, and city folks. It could be highly beneficial in late summer to the producers of food especially in the U.S. corn belt when evapo-transpiration greatly exceeds precipitation. There is no evidence that climate variability or hazardous events (floods, tornadoes, heat waves, frost, and even volcanoes) would be more frequent as atmospheric carbon dioxide increases. Market inter-annual variations have always been with us. The most recent disaster for the grain belt of the United States was the hot, dry summer of 1988. This resulted in the first major scare tactics of a global warming initiated by scientists, with hearings before Congress and ndws releases to the press. The cold, wet summer of 1992 followed. Again, 1995 wa a partial analog of that experienced in the summer of 1988.
The only major climatic change during the last 100 years in the United States to which large numbers of people have been exposed, has been in the socalled "heat island effect" experienced in metropolitan areas where large quantities of fossil energy and associated "pollutants" have been released into the atmosphere. This could be considered as good for warming in winter but bad for heat in summer. Changnon (1992) has suggested that these temperature modifications upward of 2-5 degrees C could be considered close analogs to what most computer simulations have projected for the next 50 years, and if a real world global warming were to occur. These changes have obviously been tolerated.
Food security, climate change and variability, and rising level of carbon dioxide are all resources vital to the people of the earth. Of these resources, the rising levels of atmospheric carbon dioxide must not be viewed as former senator and now Vice President Albert Gore has declare in his best-selling book Earth in the Balance (1992):
"The process of filling the atmosphere with CO2 and other pollutants--is a willful expansion of our dysfunctional civilization into vulnerable parts of the world."
Such pronouncements are too often accompanied by projections of melting icecaps, coastal flooding, mega hurricanes, drought, disease, and famine.
For the present, the direct effects of an increasing atmospheric CO2 on food production and the outputs of rangelands and forests are much more important than any effects thus far manifest for climate. A recent review of over 1,000 individual experiments with 475 plant crop varieties, published in 342 peer-reviewed scientific journals and authored by 454 scientists in 29 countries, has shown an average growth enhancement of 52% with a doubling of the current level of atmospheric carbon dioxide (Idso and Idso, 1994: Wittwer, 1995). Yet some scientists, especially those with ecological orientations, take delight in glamorizing, along with a sympathetic press, the few exceptions with, in turn, become widely quoted in the scientific literature. These include tussock arctic tundra (Oechel and Strain, 1985); some grasslands where undesirable species may, under restricted conditions, outgrow the more desirable (Wedin and Tilman, 1996); and in some ecosystems where competition among species may create a lack of balance (Bazzaz and Fajer, 1962).
Globally, it is estimated the overall crop productivity has been already increased by 10% because of CO2 and may account for much of what has been attributed to the Green Revolution. Meanwhile, changes in climate in specific fields where crops actually grow and are cultivated remain defiantly uncertain. Conversely, the effects of an enriched CO2 atmosphere on crop productivity in large measure, are positive, and leave little doubt as to the benefits for global food security.
With this note, it is a sad commentary that most of the current and modern textbooks on plant nutrition omit, inadvertently or otherwise, any mention of the role of carbon dioxide as a fertilizer or essential nutrient. This was tru 35 years ago (Norman, 1962) and remains so to this day. Textbooks still ignore the fact that different levels of CO2 may have pronounced effects on plant growth and may interrelate and complement various levels of other nutrients applied to crops in the rooting media. The complementing effects are also manifest with respect to water requirements and positive interrelations with temperature, light, and other atmospheric constraints.
Today, in the greenhouses of the Westlands of Holland, where the first use of elevated levels of greenhouse carbon dioxide for enrichments of food crops occurred 40 years ago, there are glass greenhouses covering over 10,000 hectares. These are all enriched with atmospheric levels of 1,000 ppm of CO2 during daylight hours. This practice is followed during the entire year when crops are produced. Increases of marketable yields of tomatoes, cucumbers, sweet peppers, eggplant, and ornamentals range between 20 to 40% with an annual return of $3 billion (Nederhoff, 1994).
There is currently a blind spot in the political and informational systems of the world. This is accompanied by a corruption of the underlying biological and physical sciences. It should be considered good fortune that we are living in a world of gradually increasing levels of atmospheric CO2. The satellite data on global temperature changes are now in. There has been no appreciable warming. Contrastingly, the rising level of atmospheric CO2 does not make the United States the world's worst polluter. It is the world's greatest benefactor. Unlike other natural resources (land, water, energy) essential for food production, which are costly and progressively in shorter supply, the rising level of atmospheric CO2 is a universally free premium gaining in magnitude with time on which we can all reckon for the future. The effects of the increasing atmospheric level of CO2 on photosynthetic capacity for the enhancement of food production and the output of rangelands and forests, appear far more important than any detectable change in climate. Elevated levels of atmospheric CO2 also provide a cost-free environment for the conservation of water which is rapidly becoming another of the world's most limiting natural resource, the majority of which is now used for crop irrigation.
References:
Bazzaz, F.A. and E.D. Fajer, 1992. Plant life in a CO2-Rich World. Scientific American, 266(1), 68-74.
Changnon, S.A., 1992. Inadvertent Weather Modification in Urban Areas: Lessons for Global Climate Change. Bulletin of the American Meterological Society, 73(5), 619-627.
Idso, K.E., and S.B. Idso, 1994. Plant Response to Atmospheric C02 Enrichment in the face of Environmental Constraints: A review of the Pst 10 Years. Agricultural and Forestry Meterology, 69, 153-203.
Intergovernmental Panel on Climate Change, 1996. Climate Change 1995: The Science of Climate Change. Cambridge University Press, Cambridge, England.
Nederhoff, E.M., 1994. Effects of CO2 Concentration on Photosynthesis, Transpiration and Production of Greenhouse Fruit Vegetable Crops. Glasshouse Crops Research Station, Naaldwijk, The Netherlands.
Norman, A.G., 1962. The Uniqueness of Plants. American Scientist, 50, 436-449.
Oechel, W.C., and B.R. Strain, 1995. Native Species Responses to Increased Atmospheric Carbon Dioxide Concentration. In: Direct Effects of Increasing Carbon Dioxide on Vegetation. B.R. Strain and J. Cure (Eds) pp. 117-154, U.S. Department of Energy DOE/ER-0238. Washington, D.C.
Waggoner, P.E. 1994. How Much Land Can Ten Billion People Spare for Nature? Task Force Report No. 121. Council for Agricultural Science and Technology. Amers, Iowa and Rockefeller University, New York.
Wedin, D.A. and D. Tilman, 1996. Influence of Nitrogen Loading and Species Composition on the Carbon Balance of Grasslands. Science, 274, 1720-1723.
Wittwer, S.H., 1995. Food, Climate, and Carbon Dioxide. CRC Press. Lewis Publishing, Boca Raton, FL. 236pp.
Wittwer, S.H. and W. Robb, 1964. Carbon Dioxide Enrichment of Greenhouse Atmospheres for Food Crops Production. Economic Botany, 18, 34-56