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CHAPTjlE-3 In the face of continued growth of the worlds popula- tion and enduring pressure on the planet's food-producing capacities, large natural fluctuations cf weather and cli- mate increasingly threaten human survival and well-being, particularly in less advanced countries. Projected human- induced modifications of the earth's surface and the atmo- sphere, and some changes that have already occurred, could cause effects on climate of a magnitude, spatial extent, and duration comparable to some natural fluctuations. Given the current state of knowledge of the mechanisms of climate change, it is not possible to distinguish between natural and human-induced changes, at least on global and long-term scales. Artificial change, moreover, may increase the ya.ri- abili£v. of climate, which is a crucial factor in the supply cf and demand for food. Available methods of predicting the effects on weather and climate of man-made environmental changes are inade- quate, and may never be perfected; it is generally acknowl- edged that, at best, decades of work will be required tc improve them significantly. We cannot new predict what cli- matic changes will occur; we can only indicate what might cccur. The possibilities are disturbing. The potential magnitude cf the consequences for humanity of possible cli- matic changes makes this a subject deserving the concerted attention of both the research community and those charged with protection of the environment. The situation is complicated by the fact that many of the possible man-made changes in climate that have been considered are global in character. Pollutant emission or other environmental modification in one country may affect the whole world; a nation may not be able to protect itself by its own regulations. Furthermore, most of the climatic changes that have been envisioned are neither universally deleterious nor universally beneficial to humanity. Pres- sure for regulation is unlikely to be equally strong in all regions or nations, and proposals for regulation by some sections cf the world community might be actively resisted by others. - 34 -

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IMPACTS OF CABBCN DIOXIDE EMISSIONS follow a givgn increase of the carbon of the atmosphere. The irost important climatic question facing the world today is probably the magnitude cf charges that may result from an increase in the CO2 content of the atmosphere caused by burning fossil fuels (NEC 1977). Scme authoritative projections of fuel combustion, combined with existing geo- chemical and climatic theories, indicate that a critical pcint in regard to C02 may 'be reached within the next 20 to 50 years. National and international policies defining acceptable limits on the use of fossil fuels must be estab- lished within that span. Such definitiors must be based on reliable estimates of the magnitude cf changes that might occur in global temperatures and consequent changes in climate, polar ice cap masses, and sea level. Methods involving further development of comprehensive general circulation models seem most unlikely to produce such estimates within the tirre available. EPA, the Energy Research and Development Administration (ERDA) , and other agencies responsible for energy and environmental policy should therefore support or encourage studies using less time-consuming methods, recognizing the risk of failure in- rerert in this approach. Models available today should be used, with some necessarily arbitrary simplifying assump- tions, to estimate the consequences cf projected emissions cf CC2. The results will not be precise predictions but should at least establish some reliable upper and lower boundaries for possible effects. This information is a major requirement for setting scund policies governing combustion of fossil fuels. This problem must be viewed in a larger perspective, since fossil fuel combustion is bound tc the need to feed humarity and keep it warm over the next two centuries. Fesearch should therefore also be undertaken by some fed- eral agency to examine the international, very Icng-term aspects of energy conversion and environmental change. - 35 -

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EFFECTS ON THE CZOKE LA*ER Research should continue to be cursued Atmospheric scientists have identified a number of threats to the stratospheric ozone layer in recent years, including fluorocarbon aerosol propellants and refriger- ants (Molina and Rowland 1974, NRC 1976), high-altitude emissions of nitrogen oxides in aircraft exhaust (Jchnstcn 1971, NRC 1975a), and nitrous oxide produced from fertil- izers by soil microorganisms (Crutzen 1974, Council for Agricultural Science and Technology 1976). The effect under study is a reduction of the concentration cf ozone in the stratosphere, slcwly reversible, with a time con- stant of decades. Understanding the modification of. the ozone layer appears to be a much more tractable question than that cf general climatic change. The meteorology, physics, and chemistry of the ozone layer are being vigorously studied, and it seems likely that a consensus on accept- able quantitative estimates of the reduction factors, accurate to within a factor of two or three, will be reached within a very few years. Nevertheless, much more information is needed on the biological and cli- matic consequences of .increased ultraviolet irradiation and cf related changes in radiation balances. These problems have been reviewed by the Natioral Research Council (1975a) . EPA has recently beer assigned a lead agency role in federal research on these subjects. The social and political consequences cf possible regu- latory actions also need to be studied, particularly if fertilizer use should be affected, and the international aspects of control measures must be taken into account. Although the causes of the perturbations could origi- nate in any or all countries, the deleterious effects, at least those directly concerned with human health, are likely to be limited in their occurrence to a rela- tively small geographic area (see NRC 1975a, Appendix C: 177-221). - 36 -

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EFFECTS CF SULFUF EMISSIONS dirgcted toward connected with §ulfur rand other Froblems of weather and climate modification connected with sulfur emissions include local to regional reductions cf solar radiation at the surface due to aerosols, regional increases in acidity of precipitation, and minor modifica- tion of local rainfall patterns (Metromex Investigators 1976), These problems may at times cross international boundaries (Eolin and Persson 1975). Pollutant sulfur enters the atmosphere mainly by com- bustion of coal and heavy oil. It is emitted in the form cf gaseous sulfur dioxide, but a proportion is quickly converted to sulfuric acid in the form of small particles. Sulfur emission is normally accompanied by emission of solid particles, and the emission control techrology currently in use does not remcve the finest of these particles. The solid particles are particularly efficient in reducing the solar radiation reaching the ground, since they absorb as well as scatter it. It seems very likely that control technologies will be developed to minimize sulfur emission and to reduce even further the emission cf particles, but such technologies will be expensive. The greatest infor- mation need in this area is probably or the biological and economic consequences of acidified precipitation and weather modification by sulfur and particle emission, which would need to fce balanced against the biological and social impacts of using more expensive low-sulfur fuels. INSTITUTIONAL AFBANGEMENTS Given the present state cf krowledge, research on pos- sible perturbations of weather ard climate by environmental modifications cannot, in general, be separated from other aspects of climate research. In the United States, such studies are being carried out by the Departments of Defense, Commerce (NCAA), Interior (Bureau of Reclamation), and Transportation (Federal Aviation Administration [FAA]), and by the National Aeronautic ard Space Administration (NASA), ERDA, EPA, and NSF. An Irteragency Committee on Atmospheric Science exists under the Federal Council for Science and Technology, but it seems unlikely that the cptimal administrative arrangemert has been achieved. A very large proportion of the funding is devoted to in- - 37 -

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house projects and tc wcrk in the large national labora- tories. Most of the NSF budget for climate dynamics and the atmospheric sciences goes tc the maintenance of the National Center for Atmospheric Research, and to the pur- suit of major international programs that call for long- term spending commitments. There is little flexibility that would allow support of unsolicited innovative research in universities and independent research institutes. A recent study, Understanding Climate Change (NRC 1975b), estimated the expenditure or climate-rela- ted research in 1974 "excluding essentially operational or service related activities" as $18 million per year. It called for a graduated increase to $67 million by 1980—a call that has not yet been heeded. That par- ticular NBC study was concerned mainly with the problem of global climate prediction on all time scales and had little to say about the usefulness of limited investiga- tions of specific problems, as recommended above. •the question of stratospheric modification and its consequences was examined extensively in the Climatic Impact Assessment Program (CIAP) of the Department of Transportation. This work is being continued in a more selective way in the Upper Atmospheric Programs funded through FAA and NASA. Within this program EPA has been designated the lead agency for research on biological and climatic effects. At this early stage the adminis- trative arrangements and the scope of the program appear satisfactory. The CIAP studies emphasized the interna- tional nature of problems; continuation of this aspect is essential if future regulatory action is contemplated. fcithin EPA, research on sulfur emissions at present has high priority at all levels, from techniques of fuel desulfurization to field observations cf transport and transformation of the emissions and consequent weather modification, A large, well-conducted field experiment with funding from EPA, NSF and state sources is continu- ing in the St. Louis area, and EPDA is planning a major survey of the fate and effects of sulfur emissions. If the dangers of overemphasis on data collection at the expense of critical review and analysis by independent scientists can be avoided, the level of effort seems commensurate with the importance of the problem, but frequent review is vital. - 38 -

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REFERENCES Eolir, B. and C. Persson (1975) Regional dispersion and deposition of atmospheric pollutants with particular application to sulphur pollution over Western Europe. Tellus 27:281-310, Council for Agricultural Science and Technology (1976) Effect of Increased Nitrogen Fixation on Strato- spheric Ozone. Report No. 53. Ames, Iowa: Council fcr Agricultural Science and Technology. Crutzen, P.J. (1974) Estimation cf possible variations in total ozone due to natural causes and human activities. Ambio 3:201-210. Johnston, H.S. (1971) Reduction cf stratospheric ozone by nitrogen oxide catalysts from supersonic transport exhaust. Science 173:517-522. Metrcmex Investigators (1976) Metromex update. Bulletin cf the American Meteorological Society 57:304-308. Molina, M.J. and F.S. Rowland (1974) stratospheric sink for chloroflucrometbanes—chlcrire atom-catalyzed destruction of ozone. Nature 249:810-812. National Research Council (1975a) Environmental Impact of Stratospheric Flight. Climatic Impact Committee, Assembly of Mathematical and Physical Sciences. Washington, B.C.: National Academy of Sciences. National Research Council (1975b) Understanding Climate Change: A program for action. The C.£. Committee for the Global Atmospheric Research Program. Washington, c.c.: National Academy of Sciences. National Research Council (1976) Halccarbons: Effects or Stratospheric Ozone. Panel on Atmospheric Chemistry, Committee on Impacts of Stratospheric Change, Assembly cf Mathematical and Physical Sciences. Washington, C.C. National Academy of Sciences. National Research Council (1977) Energy and Climate: Cuter Limits to Growth? Geophysics Study Committee, Geophysical Research Board, Assembly of Mathematical and Physical Sciences. Washirgtcn, D.C.: National Academy of Sciences, - 39 -