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Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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33
Methods and Tools

Methods of Adaptation

Although one cannot be sure how nature and humanity would cope with a new climate, past hazards of weather and changes of climate and the seasons and climates on the planet today give hints of impacts and adaptations.

Adjustment by Nature

Nature on a given tract of land is a system, or ecosystem, of plants, animals, and microbes. If circumstances do not change in a very old forest, for example, the system may cycle with little change in composition in the manner shown by the circle on the left of Figure 33.1. If circumstances change, however, the system adjusts to an alternate composition through a succession as some species grow less numerous while others flourish because they are better suited to the new circumstances. Because flowering, fruiting, and germinating of seed are sensitive to climate, the first adjustment in a system in response to changing climate would probably be failure of some present species to reproduce. This would be followed by the chancy stage of invasion of new species from outside or expansion of species already on the tract but formerly held in check. An opening, the presence of a seed, and the arrival of a seed are all random events in nature. This stage is depicted on the right of Figure 33.1.

Fossils show that, during a climate change, trees lag in adjustment behind other organisms, because either the dispersal of seeds or the development of soils is slow. Disturbances like fires have accompanied past changes in climate and speeded up the adjustments in vegetation. Trees might persist despite a rapid warming or cooling but then be disturbed by a fire,

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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image

FIGURE 33.1 Growth, thinning by competition, and death of a tract of forest is a cycle.

NOTE: The stage of Death/Regeneration is the ''most stochastic" or most uncertain stage. It could lead
to "alternate composition" of the forest, that is, a succeeding and different species mix.

SOURCE: Reprinted, by permission, from Shugart et al. (1986). Copyright © 1986 by SCOPE.

storm, or pest. With the death of the persistent trees, the forest would then adjust more rapidly.

Other forces will likely affect the natural system on the tract and its adjustment to climate. People may clear, plant, manage, or abandon the tract; storms could uproot the trees; or fires might blacken the landscape. Their impacts may obscure or modify those of climate change. Or, as explained above, they may hasten the adjustment of the forest to the new climate.

An alternative to thinking of the adjustments on a given tract of land is thinking of the migration of an ecosystem or community from tract to tract in response to climate changes.

Communities are composed of species populations … connected by a web of interspecific relationships that have evolved over thousands or millions of years. If entire communities or all the species except for a few minor ones migrate, these community interactions may be preserved. In the highly disturbed

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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and man-influenced global ecosystem, however, it is doubtful that intact ecosystems can survive by migration. (Strain and Bazzaz, 1983)

Still another way of thinking of changes in organisms is to think of an individual species. Within a species, under a changed climate, natural selection would favor the combination of genes that was best suited to the new climate and would tend to eliminate other combinations. If no individuals within the species could compete successfully in the changed climate or were not present or could not reach a favorable climate elsewhere, the species could be extinguished.

Instead, if climate changes rapidly, new communities or ecosystems dominated by pioneer rather than climax species are likely to emerge on the margins of zones and populations. There, long-lived things like trees would persist, but if they were ill adapted would fail to reproduce. New kinds of life fitted to the new climate would grow up through the persisting individuals, sometimes hastened by a disturbance. Adapted species already present in a mixture or pioneers from afar could have an advantage in the new climate.

Adaptation by Humanity

The range of climates where people live successfully indicates that societies can cope with wide variations in climate. The main way that people adapt to changing climate is by adapting to variability in climate. This is especially true when people are regularly adapting to changes in farming, forestry, construction, and all the other changes that require one to discard old and take up new ways of doing things. Disasters caused by severe weather and degradation of the environment do, nevertheless, illustrate the kinds of large disruptions that could accompany change and adaptation. What lessons can we learn from the adaptations people have made?

The first lesson arises from a survey of the types of responses to hazardous events made in dozens of cases. Although rapid and continuous climate change might eventually outstrip the efficacy of these adjustments that worked for extremes in the past climates, they nevertheless provide a menu of five potential choices: (1) modify the hazard, as by seeding clouds; (2) prevent or limit impacts, as by dikes; (3) move or avoid the loss, as by flood plain zoning; (4) share the loss, as by insurance; and (5) bear the loss, as by rebuilding a house (White, 1974; Burton et al., 1978).

Additional factors affecting this simple menu are whether the adjustment is made before or after an event and whether the adjustment is understood, practical, and affordable. Another factor is the possibility that a climate change might be helpful rather than hazardous. Figure 33.2 separates the adjustments into purposeful and incidental kinds and shows whether they precede or follow an event.

By adjusting to extremes of the current climate, society has already made

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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image

FIGURE 33.2 A choice tree.

NOTE: Adjustment begins with an initial choice of a resource use, livelihood system, and location. For that choice
various incidental and purposeful adjustments are available, at somewhat different time scales for initiation.
The most radical choice is to change the original use or location.

SOURCE: Reprinted, by permission, from Burton et al. (1978). Copyright © 1978 by Oxford University Press.

investments that would absorb some climate change. The United States has invested $70 billion to $80 billion in local and regional controls for water from storms and floods. Much is invested in heating and air conditioning, coastal protection, and irrigation.

Even in exposed activities like managing water and farming, the capacity to adapt can be high, although the cost may also be high. Past responses are analogs that illuminate how well society might deal with future climate change (Glantz, 1988). One such example was supplied by Indonesia, which set the goal of improving rice growing to make the country self-sufficient during the 1980s. In 1982–1983 a severe drought cut the yield 10 percent or more in some areas, slowing the attainment of self-sufficiency. Farmers, however, planted more off-season crops and increased the yield of second-crop rice through careful cultivation and management of water. So despite the drought, rice production was resilient, production in no province returned to the low levels before 1980, and within 2 years the trend toward self-sufficiency was restored (Malingreau, 1987). While the Indonesian farmers adapted to a drier situation that proved temporary, this example shows the character of adaptation. Moreover, in a world of rapidly and

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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continually changing climate, many adaptations will necessarily have a temporary orientation.

In the United States, water managers have sometimes decreased the annual fluctuations in supply without large construction projects. In California, managers worked with users to reduce peak demand and accommodated annual differences in supply. They explicitly recognized climate instability and built adjustments to extremes of wet and dry into reservoir operations. The new procedures smoothed out the feast and famine caused by the old procedure. In Arizona, a quick and effective adaptation to a series of wet years occurred during the early 1980s (Phillips and Jordon, 1986; Riebsame, 1988).

Adaptation is part of the interaction between society and its environment. Prompt and effective adaptation in that interacting system requires information. It requires that messages be sent and, a rarer thing, that messages be perceived. The clearest lesson from the study of natural hazards is that the key obstacles are not technical but rather involve economics, information, and perception of the threat (Mitchell, 1984).

Messages about a slow change in climate could be misread in two ways, underreading and overreading. Years of experience slant our expectation of the climate of the next decade toward the past one, which is underreading if climate is changing. For example, managers of water systems reported they would keep designing for the climate of the past until they saw a change or heard from a consensus of distinguished authorities that it was changing (Morrisette, 1988; Schwarz and Dillard, 1990), and other professions have a similar expectation of stable climate (Holling, 1986).

If climate is not changing, overreading could be caused by occasional extremes, even though they are only manifesting the variability of the past. In the mid-nineteenth century the myth spread that the climate of the Great Plains was permanently changed for the better and that human settlement itself would improve it further. After farmers flooded into the largely uncultivated margins of the frontier, the forgotten variability of the weather brought drought, and the drought displaced nearly 300,000 Great Plains farmers back to the East and out to the West Coast (Warrick and Bowden, 1981). The hot summer of 1988 cannot be proven to be part of climate change, but many saw it that way, illustrating the potential influence of extreme events on debates over the reality and significance of climate change.

Environmental problems that elicit action are generally those that are serious, soon, certain, and soluble. The last point is key, since experience with the mitigation of natural and technological hazards has shown that people respond less effectively when information about the problem stresses its causes and nature rather than possible solutions. Information about climate must be connected to the experiences of real people and to specific and feasible adjustments or it will be ignored. Because climate change is

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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neither certain nor soon and not easily soluble by a few people, remedies for related, more certain problems like drought should be stressed and linked to climate change where feasible. Examples are suggested below (White, 1988; Ingram et al., 1990; Riebsame, 1990).

Since people feel the events of the moment or year, not the trend line, they will be affected by and adapt to the size or frequency of extremes. We react more strongly to worsened storm surges than to a gradual rise of the sea, more to droughts than to lower average precipitation, and more to heat waves than to gradual warming.

In the United States the history of responses to natural hazards is one of major events calling forth rushes of legislation (May, 1985; National Research Council, 1987). Some of these events have evoked investments that greatly increase our adaptability to climate change. Other investments may delay lasting adaptation, like disaster aid that encourages reconstruction on a flood plain, or the response of the markets and the government to the summer of 1988 that encouraged the expansion of dryland farming in North Dakota (White, 1975; Riebsame et al., 1991), or the planting of citrus trees in freeze-prone sections of Florida (Miller and Glantz, 1988).

Yet another lesson is that the impacts of climate change can be greater at margins of climatic zones and for impoverished people. For example, in the center of the Corn Belt fewer droughts might raise corn yields only a bit, whereas on the belt's dry western margin it could make corn a profitable crop. Where people are poor and food costs much of their income, they may not have the mobility to escape nor the money to import food when drought kills crops. One bad climatic extreme can consume much of the gross national product (GNP) of a small country, as has happened in Tanzania and Nepal (Kates, 1980). Places and people with more resources adapt more easily than those at the margins.

The Tools of Innovation

Much of the interaction between climate and humanity is technological invention of the "hardware" and "software" tools that are at the heart of adaptation (Ausubel, 1991). The hardware includes tractors that can cultivate large tracts in a few days if spring is late and air conditioners that make hot days comfortable. The software is new information, rules, and behaviors such as weather forecasts, insurance restrictions, and repair of leaky faucets. Software is usually indispensable for adopting new hardware. Major breakthroughs like irrigation usually depend on clusters of new social organization and financing as well as new machinery.

Many past innovations in hardware and software have helped people adapt to climate and variable weather: in 1873, preservatives for food in warm weather; in 1879, incandescent bulbs for dark days; in 1885, gasoline-powered

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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automobiles to travel the open road; in 1887, aluminum to resist corrosion; in 1895–1906, refrigeration and air conditioning for heat waves; in 1916, windshield wipers and in 1927, ethylene glycol antifreeze to make travel easy in all weather; in 1930, the first sales of frozen food to span summers; in 1934, radio beam navigation; and in 1960, weather satellites to cope with storms. The technology that allows humans to adapt to long-term climate change will mostly be like that tempering the difference between daytime warmth and nighttime cold, protecting us against storms and heat waves, and helping us live in diverse climates today. No qualitatively new technologies have been proposed to ease adaptation to climate change that may be caused by greenhouse gas emissions.

Experience shows that innovation can be fast in comparison with the climate change envisioned for the next 50 to 100 years. In 1900 dry California had a small crop production, and in 1985 it produced twice as many dollars of crops as second-place Iowa. In 1903 at Kitty Hawk the Wright brothers flew 59 seconds in a favorable wind, and in 1985 in the United States 380 million airplane passengers flew 336 billion miles in all kinds of weather. Penicillin was discovered in 1928, and by 1945 it was saving lives. The microprocessor was introduced in 1971, and in 1990 Americans were using 50 million personal computers (PCs). Both the character and the extent of the impacts of climate change, and adaptation to it, will in large part be a function of the rates of innovation and diffusion of the technologies that continue to transform the human economy.

Even though inventions and their adoption may occur quickly, we must ask whether the broad spectrum of current capital investments could be changed fast enough to match a change in climate in 50 to 100 years. As shown below, this period will comfortably allow the replacement of major technological systems.

In fact, 50 years is enough time to turn over most capital stock. About two-thirds of capital stock is usually in machinery and equipment and one-third in buildings and other structures. In Japan the average renewal period for capital stock in business—the time it takes for machinery and equipment in an industry to be almost entirely replaced—ranges from about 22 years in textiles down to 10 years or less in such fast-moving industries as telecommunications and electrical machinery (Economic Planning Agency, 1989). Renewal is fast in agriculture, too. The estimated life span of the cultivars—varieties that have originated and persisted under cultivation—of five major crops in the United States is less than 10 years, and most experts believe the life span of cultivars will grow shorter (Duvick, 1984).

Figure 33.3 shows the similar youth, compared to greenhouse effects, of the capital stock in the Federal Republic of Germany (FRG) and the USSR for both machinery and such structures as buildings and pipelines. For the FRG in 1985 some 60 percent of the stock of structures was less than 20

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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FIGURE 33.3 Age distribution of nonmachinery capital stock in the FRG
for 1985 (white bars) and in the USSR as of 1986 (black bars).

SOURCE: Courtesy of Jesse Ausubel.

years old (Statistiches Bundesamt, 1989). In the USSR in 1986 some 80 percent was less than 20 years old (USSR State Committee on Statistics, undated).

At first such figures may seem surprising. Some of our surprise arises from the justifiable value and thus attention we give to precious monuments and localities like the cathedral of Notre Dame or the city of Venice. Some reflection on the total equipment and buildings we use daily, however, relieves our surprise at seeing Figure 33.3. Consider the office space in a city, whether Hong Kong, Milan, or Denver. Most of the space is in buildings built in the last 20 years. These new buildings are filled with such new equipment as telephone systems. Indeed, even older buildings are filled with modern equipment, such as PCs and FAX machines, that did not even exist 15 or 20 years ago. The same is true for supermarkets, restaurants, and other stores, many of which are less than 20 years old and in any case have modern cash registers and furnishings. A large fraction of residences is similarly young and, in turn, filled with new appliances of all kinds. In fact, if societies grow at 2 to 3 percent per year, as industrialized societies have for the past 150 years, then half of all capital stock will always be less than 30 years old.

Probably the systems that take the longest to build are infrastructures that provide transport, energy, water, communications, and means of meeting other human needs. Once constructed, many infrastructure systems are (or should be) continuously reconstructed. For example, roads are resurfaced

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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every decade or so, depending on use. The time required for societies to bring forth such systems can be found. They are typically completed in 50 ± 20 years (Grübler, 1990). The 7,000-km canal system of the United States was almost entirely built in about 30 years, between 1820 and 1850. More than 90 percent of the 300,000-mile U.S. railway network was laid in the 65 years between 1855 and 1920. The paving of virtually the entire 6 million-km surface road system of the United States was accomplished between 1920 and 1985. The U.S. interstate highway system was completed, with some localized exceptions, in about 30 years from the time that it was announced by President Eisenhower. It is interesting to consider whether climate change could require any public works on this scale; coastal protection and interbasin water transfer would seem the most likely candidates. Because the siting process for infrastructures can be lengthy, siting is needed early if a decision is anticipated in favor of construction of a major new infrastructure to adapt to changing climate or rising seas.

Because capital stock is continuously turning over on a time scale of a few decades, it will be possible to put in place much technology that is adjusted to a changing climate. This can be done without extraordinary measures given reasonably accurate information about the future. For the shortest lifetimes, even accurate information about the present climate will do. The fact that perhaps 90 percent of the capital stock in place in the year 2040 will have been built after 1990 does not diminish the significance of some long-lived structures. Action may be necessary to protect cities such as Venice, where preservation of historic buildings is the goal. In such cases the fact that much new investment outpaces climate change is not helpful, as processes of replacement are not relevant. However, there is time to do what may be indicated, if the political will and money exist.

Innovation contributes toward making human society less subject to natural phenomena, at least in the short term. With current technology, people can live in virtually any climate that now exists. Heating and cooling, along with medicine and sanitation, have enabled many to inhabit regions that were previously uninhabitable, although reducing vulnerability further may become more difficult and expensive if long-term problems of energy and water availability are not solved. At the same time, it is hard to envision how natural ecosystems could possibly be climate-proofed.

However, it is innovations and technology along with population and economic growth that are currently causing many global changes, not only in climate (increases in CO2, CH4, N2O, and chlorofluorocarbons [CFCs]) but also in depletion of the ozone layer (CFCs), pollution, habitat degradation, etc. Thus, technology and growth, at least in our recent experience, come with prices that were unforeseen, including higher energy consumption. As a result, exclusive reliance on technology to adapt to climate must be viewed with caution.

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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Just as settlement has become feasible nearly everywhere, production can now proceed continuously, or nearly so, in severe environments. Pumps extract oil 24 hours a day, 365 days a year, in the stormy North Sea. Consumption is also becoming insulated from the environment, not only in Minneapolis and Houston, but also to some extent in New Delhi and Bangkok. Inside shopping malls, only fashions and decorations signal the season. Sports are played increasingly under domes where fans do not know whether it is windy or pouring outside. Where people must be aware of weather, they can prepare for it, because forecasts have become much more accurate in the past two decades, especially in temperature latitudes (World Meteorological Organization, 1988).

Improved technology and social organization seem to have lessened the impacts of climate fluctuations on farming during the past 100 years in the United States (Warrick, 1980). Further evidence for the "lessening hypothesis" is found in a flattening of monthly rates of total mortality in Japan between 1899 and 1973. The flattening is explained in part by the diminution of winter and summer mortality peaks that used to be associated with exposure to cold and heat (Weihe, 1979). That the peak season for vacations in developed countries is late summer—a peak season for labor in agricultural societies—further indicates the transformation that has taken place.

Making Decisions in an Uncertain World

A facile recommendation about adaptation is "factor in climate change." We, however, are and will remain uncertain about climate change and its effect on temperature, moisture, and sea level. We shall be especially uncertain of the specifics for a locality where people are mulling over the construction of a dam, bridge, or seawall. So, what method can factor in climate change?

One method is to postpone decisions until the climate prediction is less uncertain. In an economic analysis, decisions concerning climate change were exemplified by whether or not to build a seawall. The economical course turned out to be to lay the foundation for the wall and wait to learn more before spending more (Yohe, 1990).

Uncertainty is generally lowered by cycles of prediction followed by observation, testing the prediction, and revising it. So long as prior predictions are iffy, however, the revised or posterior predictions later in the cycles will be only a little more certain (Fiering and Matalas, 1990). Given this prospect of continuing uncertainty, a method is needed for decisions about adaptation during the building of things with long lives. Although much equipment and even buildings have lives shorter than the periods thought of for climate change, some urban infrastructure is long lived. The

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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cost of modifying or adapting it later is likely to be large in comparison with the cost of the initial adaptation.

As an example think of building a new bridge over an estuary. Ignore the possibility that the traffic to justify the bridge may not come in 50 years. Imagine that during construction $100,000 today will buy the adaptation of an added meter of height above sea level. Let it happen that after 50 years the sea rises and the bridge without the added clearance needs a $5 million retrofit or adaptation. Discounted at 6 percent per annum, the present value of the $5 million is $271,000. If we are certain the sea will rise, adding the meter for $100,000 makes a benefit of $271,000 minus $100,000. In general, adaptation during construction is economical as long as the ratio of the cost of a present adaptation divided by the present value of the retrofit is less than the probability of higher seas, and other superior investment opportunities are not available. Thus, in the example above, probabilities greater than 100,000/271,000 or 0.37 would justify the added investment.

Let the justified cost be in cents warranted now for a dollar of retrofit later. The probability that the adaptation will be needed, how long the wait before it is needed, and the discount rate set the justified cost, as illustrated in Figure 33.4. The mathematics in the figure's caption shows a percentage rise in the probability that the adaptation will be needed raises the justified cost by the same percentage. Regardless of how long the wait or how great the discount, raising the probability that the bridge must be adapted by 10 percent from, say, 50 to 55 percent raises the justified cost by 10 percent from, say, 20 to 22 cents—10 percent more probable, 10 percent more cost today justified by this calculation.

On the other hand, either raising the discount or lengthening the wait by 1 percent lowers the justified cost by 1 percent times the discount rate times the wait. The percentage rise in the justified cost caused by a percentage fall in discount or wait is their product: discount rate times years. Imagine lowering the product of discount times wait 1 percent from 6 percent times 100 years to either 6 percent times 99 years or 5.94 percent times 100 years. This raises the justified cost by 1 percent times 0.06 times 100, or fully 6 percent. If the justified cost before was 20 cents, it rises to 21.2 cents.

Figure 33.4 shows the justified costs for three combinations of years, discount rate, and probability of need. The center row of bars could be labeled either 50 years at 6 percent or 100 years at 3 percent. Lower discount rate, shorter wait, and higher probability or certainty raise the warranted expenditure. Lifting the justified cost of the present adaptation above 10 cents per dollar retrofit takes probabilities above 0.4 plus discounts below 3 percent and waits shorter than 50 years.

The percentage change in the justified cost always equals a percentage change in probability of need but is the discount rate times the years of wait

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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image

FIGURE 33.4 The justified cost of an adaptation in cents justified now for a dollar of retrofit later.

NOTE: The probability that the adaptation will be needed because, say, sea level rises is shown from left to right. The front row of short bars pertains to a wait of 100 years before the adaptation is needed and a discount rate of 6 percent. The back row of bars rising above 20 cents pertains to a wait of only 50 years and a discount rate of only 3 percent. Since the justified cost is approximately set by the product of discount rate and wait, the middle row, for example, could have been labeled 100 at 3 percent as well as 50 at 6 percent.

A little mathematics illustrates several points about justified costs. Let the ratio j be the cost of a present adaptation relative to the cost of retrofit. It is cents per dollar in the figure. Adaptation during construction is warranted as long as the ratio j of the costs is less than

j´ = P/(1 + i)n

where P is the probability of need, i is the discount rate, and n is the years until adaptation is needed. For commonplace discount rates, the approximation is

log(j´) image log(P) - (in)

The approximation explains why the justified cost is set by the product of the discount rate and the wait. It explains why the middle row in the figure, for example, could have been labeled either 100 years at 3 percent or 50 years at 60 percent.

The approximation is convenient for thinking about such relative changes or elasticities as (dj/j´)(dP/P). The elasticity of j´ for a change in the probability P is simply 1; for a change in (in), it is (in).

Because the elasticity of j´ for a change in P is 1, a 10 percent improvement in certainty or P always raises justifiable cost 10 percent. On the other hand, the elasticity for changes in discount times years is (in). The higher i and n, the bigger the percentage change in the ratio j´ for a percentage change in (in). The justifiable cost rises from left to right by the same percentage as the probability, but it rises more between the middle and rear rows than between the front and middle rows.

SOURCE: Figure courtesy of Jon Liebman.

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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times the percentage change in rate or wait. So for rates times waits like 0.06 times 100, foretelling rates and waits has more leverage than raising the probability of need.

Choosing a discount rate is clearly exactly as important as forecasting the length of wait. In Chapter 32, the section ''Assumptions," the panel set rates of 3, 6, and 10 percent.

So in the face of this uncertainty, rational people will start work on more adaptations than they complete. They will make more adaptations as their certainty grows. And they will pay special attention to how high the discount rate and how long the wait.

Partial Justifications and Multiple Goals

Many of the ways used and proposed for adaptation to climate change are justified only partly on the basis of climate change. For example, farmers build irrigation systems to increase current yields and to diminish the effects of variable weather. The prospect of climate change provides an additional justification for investment in irrigation. In almost all cases discussed in this report, climate change provides only a partial justification for particular actions or investments. For example, stricter zoning of shorelines could serve not only to minimize the impacts of sea level rise but also to lessen habitat destruction. Planting trees in urban areas would provide shade and comfort if the climate became hotter and would also make a small contribution to retaining carbon in the biosphere. Several actions that are proposed to lower greenhouse gas emissions, like reduction in coal usage, are similarly proposed because they serve multiple goals.

One adaptation has the virtue of shortening the wait for benefits: thorough adaptation to the present variability of weather. For example, Gleick (1990) found that among five indicators a small storage capacity relative to supply was the one that most frequently indicated vulnerability of water systems in the eastern United States. If more storage capacity were built to adapt to present variability, it would also be an adaptation to a change to a drier climate.

Thus, we must ask whether a set of partial justifications, including climate change, adds up to a full justification. From efficiency of water and energy use to coastal zone management, one could argue that these are things that societies already ought to be doing anyway. Does climate change then put certain projects over the investment hurdle? If not, how impressive are these remedies and what are the obstacles to them? Like suitors, solutions court problems; the problem of climatic change is used to justify numerous solutions. One must ask why these solutions have not yet been accepted. Gaining acceptance may well require removing a fundamental obstacle like cost, convenience, or ignorance rather than merely adding another justification.

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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Criteria for Using the Tools of Government

Government can speed adaptation with many tools. One is to provide timely information, like weather forecasts. Another is to support fundamental research, which is primarily sponsored by governments. To go beyond these unexceptionable actions to regulation or investment, however, one must examine the criteria for using government tools.

Although the most important and by far the greater number of adaptations are made by private agents like consumers and enterprises, governments can ensure that the legal and economic structure encourages adaptation. Changing incomes, prices, and environment cause more or less automatic adaptations. These include migration of capital and labor along with technology evoked by changing conditions. Buildings will be built above an advancing sea, people escape unpleasant climates, and agricultural and industrial capital leave lands that lose their advantage.

But governments can ensure that climatic impacts are translated into signals of price and income that spur private adaptation. This may be hard because many impacts of climate change are improperly priced. For example, climate change will probably alter runoff. But in the United States and most of the world, water is often not allocated efficiently and may not be when its availability changes (Frederick and Kneese, 1990). So governments can speed adaptation by using such devices as water auctions that dispatch resources to the most valuable uses as shown by the ability to pay.

Now, recur to the fallacy of conceiving a slowly changing climate as a blow on today's world and of ignoring the inevitable evolution during the coming decades. That is, think again of the "dumb people scenario" and the challenge of integrating the outcome of a changing climate with other changes that will occur during the coming decades. During this evolution it is probably unwise to prescribe in detail much adaptation now to smooth the transition to climate change over the next century. Like generals building a Maginot Line in the wrong place, we might bankrupt ourselves building dikes against floods that never come. In addition, the evident speed of innovation and replacement allows us to wait in most cases until we see the whites of the enemies' eyes. Financial markets adjust in minutes, labor moves in a few years, the economic long run is no more than two decades, and only major technologies like highways replacing rails or one school of thought forcing out another take as long as climate change.

Thus, three criteria for government action to promote adaptation can be that (1) the amount of time needed to carry out the adaptation is so long that we must act now, (2) the action is profitable even if climate does not change, and (3) the penalty for waiting a decade or two is great.

Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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Suggested Citation:"33 Methods and Tools." Institute of Medicine, National Academy of Sciences, and National Academy of Engineering. 1992. Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC: The National Academies Press. doi: 10.17226/1605.
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Global warming continues to gain importance on the international agenda and calls for action are heightening. Yet, there is still controversy over what must be done and what is needed to proceed.

Policy Implications of Greenhouse Warming describes the information necessary to make decisions about global warming resulting from atmospheric releases of radiatively active trace gases. The conclusions and recommendations include some unexpected results. The distinguished authoring committee provides specific advice for U.S. policy and addresses the need for an international response to potential greenhouse warming.

It offers a realistic view of gaps in the scientific understanding of greenhouse warming and how much effort and expense might be required to produce definitive answers.

The book presents methods for assessing options to reduce emissions of greenhouse gases into the atmosphere, offset emissions, and assist humans and unmanaged systems of plants and animals to adjust to the consequences of global warming.

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