The Ghosts of Climates Past and the Specters of Climates Future
8. Uncertainties and Anxieties
Most economic studies of the impacts and policies concerning climate change are based on scenarios like the smooth and gradual warming depicted in Fig- ure 7. And, as indicated in the last section, the conclusion that emerge from most economic studies is t o impose modest restraints, pack up our tools, and go on t o other more pressing problems. Given the high costs of con- trols and the modest projected impacts of a 1 t o 3OC warming over the next half century, how high is global warming on an international agenda that in- cludes exploding population in the South, nuclear proliferation in the Middle East, collapsing economies in the East, increasing cycles of poverty and drug use along with stagnating incomes in the West, and sporadic outbreaks of violence and civil war just about everywhere?
Given the modest estimated impact of climate change along with our other urgent concerns, we might conclude that global warming should be demoted t o a second-tier issue. Yet, even for those who downplay the ur- gency of the most likely scenarios for climate change, there remains a deeper anxiety about future uncertainties and surprises. Scientists raise the specter of shifting currents turning Europe into Alaska, of mid-continental drying transforming grain belts into deserts, of great rivers drying up as snow packs
disappear, of severe storms wiping out whole populations of low-lying re- gions, of surging ice sheets raising ocean levels by 20 t o 50 feet, of northward migration of old or new tropical pests and diseases decimating the temperate regions, of environmentally induced migration overrunning borders in search of livable land. Given the potential for catastrophic surprises, perhaps we should conclude that one of the major concerns, if not the major concern, lies in the uncertainties and imponderable impacts of climate change rather than in the smooth changes foreseen by the global models. optimization models)? Should not we be ultraconservative and tilt toward preserving the natural world a t the expense of economic growth and develop- ment? Do we dare put human betterment before the preservation of natural systems and trust that human ingenuity will bail us out should Nature deal us a nasty hand?
Faced with this dilemma, we might be tempted t o say that such ques- tions are beyond the capability of rational analysis and turn the decisions over t o philosophers and politicians. But, in fact, natural and social sci- ences have a n important role t o play in analyzing potential future outcomes and delineating potential responses. Society often requires that decisions be made in the absence of complete information, whether the decisions be military strategy, oil drilling, or research and development. In each case, a reasoned decision process involves listing the events that may occur, esti- mating the consequences of the events, judging the probabilities that each of the events will occur, weighing the expected value of the consequences against the expected costs under different courses of action, and choosing the action that maximizes the expected value or utility of the outcome.
Reasoned decision making under uncertainty is no different for climate- change policy than for other areas, although it may be more complex and require crossing traditional disciplinary boundaries more often. In think- ing through the appropriate treatment of future surprises, to the natural scientists falls the crucial task of sorting through the apocalyptic scenarios and obtaining rough judgments as t o the likelihood of different geophysical outcomes so as t o distinguish between the likely, plausible, possible, and virtually impossible. To the social scientist falls the issue of assessing the
probabilities, determining t h e values of different outcomes, a n d devising sen- sible strategies in t h e face of such massive uncertainties. T o o u r leaders falls t h e b u r d e n of ultimately deciding how t o weigh f u t u r e perils against present costs. For all, this is a fruitful use of o u r collective talents, full of intellectual challenges a n d practical payoffs.
References
China, 1992, Climate Change due to the Greenhouse Effect and its Implications for China, Study Sponsored by the World Bank, the World Wildlife Fund for Nature, and the State Meteorological Administration of China.
Cline, W., 1992, The Economics of Global Warming, Institute of International Economics, Washington, DC, USA.
EPA (US Environmental Protection Agency), 1989, The Potential Effects of Global Climate Change on the United States: Report to Congress, EPA-230-05-89-050, December.
Fankhauser, S., 1993, The Economic Costs of Global Warming: Some Monetary Es- timates, pp. 85-105 in Y. Kaya, N. NakiCenoviC, W. Nordhaus, and F.L. Toth, eds., Costs, Impacts, and Benefits of CO2 Mitigation, CP-93-2, International Institute for Applied Systems Analysis, Laxenburg, Austria.
Gaskins, P.W. and Weyant, J.P., 1993, EMF-12: Model Comparisons of the Costs of Reducing CO2 Emissions, American Economic Review 83(2):318-323.
Huntington, E., 1915, Civilization and Climate, Shoe String Press, Hamden, CT, USA.
Hammitt, J .K
.,
Lempert, R.J ., and Schlesinger, M.E., 1992, A Sequential-decision Strategy for Abating Climate Change, Nature 357(May):315-318.IPCC (Intergovernmental Panel on Climate Change), 1990, Climate Change: The IPCC Scientific Assessment, J.T. Houghton, G.J. Jenkins, and J.J. Ephraums, eds., Cambridge University Press, New York, NY, USA.
Jorgenson, D.W. and Wilcoxen, P.J., 1991, Reducing US Carbon Dioxide Emissions:
The Cost of Different Goals, pp. 125-128 in J.R. Moroney, ed., Energy, Growth, and the Environment, JAI Press, Greenwich, C T , USA.
Kamarck, A.N., 1976, The Tropics and Economic Development: A Provocative In- quiry into the Poverty of Nations, The Johns Hopkins University Press, Balti- more, MD, USA.
Kolstad, C.D., 1993, Looking vs. Leaping: The Timing of COz Control in the Face of Uncertainty and Learning, pp. 63-82 in Y. Kaya, N. NakiCenoviC, W.
Nordhaus, and F.L. Toth, eds., Costs, Impacts, and Benefits of CO2 Mitiga- tion, CP-93-2, International Institute for Applied Systems Analysis, Laxenburg, Austria.
Liverman, D.M. and O'Brien, K.L., 1991, Global Warming and Climate Change in Mexico, Global Environmental Change(December):351-364.
Manne, A.S. and Richels, 1990, R.G., C 0 2 Emission Limits: An Economic Cost Analysis for the USA, The Energy Journal 11(2):51-74.
Manne, A.S. and Richels, R.G., 1992, Buying Greenhouse Insurance: The Economic Costs of COz Emission Limits, MIT Press, Cambridge, MA, USA.
NAS (National Academy of Sciences), 1992, Committee on Science, Engineering, and Public Policy, Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base, National Academy Press, Washington, DC, USA.
Nafziger, E.W., 1990, The Economics of Developing Couniries, Wadsworth, Bel- mont, CA, USA.
National Research Council, 1979, Carbon Dioxide and Climate: A Scientific Assess- ment (National Academy Press, Washington, DC, USA.
Nordhaus, W.D., 1979, The Efficient Use of Energy Resources, Yale University Press, New Haven, C T , USA.
Nordhaus, W.D., 1991, To Slow or Not to Slow: The Economics of the Greenhouse Effect, The Economic Journal 101(July):920-937.
Nordhaus, W.D., 1992a, How Much Should We Invest to Slow Climate Change?
pp. 271-299 in H. Giersch, ed., Policies on Economic Growih, Springer-Verlag, Berlin, Germany.
Nordhaus, W.D., 1992b, An Optimal Transition Path for Controlling Greenhouse Gases, Science 258:1315-1319.
Nordhaus, W.D., 1994, Managing the Global Commons: The Economics of the Greenhouse Effect, MIT Press, Cambridge, MA, USA.
Peck, S.C. and Teisberg, T.J., 1992, CETA: A Model for Carbon Emissions Trajec- tory Assessment, The Energy Journal 13(1):55-77.
Ramsey, F.P., 1928, A Mathematical Theory of Saving, The Economic Jour- nal(December):543-559.
Reilly, J . and Hohmann, N., 1993, Climate Change and Agriculture: The Role of International Trade, American Economic Review 83(2):306-312.
Streeten, P., 1972, The Froniiers of Economic Developmen2, Wiley, New York, NY, USA.
Todaro, M.P., 1991, Economic Developmen2 in 2he Third World, Longman, New York, NY, USA.