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Such an outcome would produce yet other conflicts. The controversies about global change are only partly fact-based. True, some of the disagreements might fade with better knowledge about the global environment and the likely effects of different feasible responses. As it became clear that expected global warming over the next 50 years could not cause the breakup of the West Antarctic icecap, the flood-prevention rationale for slowing greenhouse gas emissions became considerably weaker.

A response such as dike building seems much more appropriate when the sea threatens only a few areas.

And if it became clear what each policy option—at the local, national, and international levels—would accomplish if enacted, some of them could easily be rejected. But knowledge often fails to resolve controversy. It frequently raises new disputes or calls old beliefs into question. And even when new knowledge reduces uncertainty, controversies persist because not only facts, but also important interests and values, are at stake. Informed people disagree because the remaining uncertainty leaves room for judgment, because they may assume different scenarios about the future of society, and because an outcome that harms what one person values may enhance what another values.

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Those impressed with the potential benefits of economic growth tend to line up against those who fear of the. When faced with choices, some prefer international solutions to global problems, others see national action as more feasible; some favor market adaptations, others, community-based action outside the market and the state; some are attracted to large-scale technological solutions, others see them as cures that may be worse than the disease. In short, the debates are not only about the workings of human and environmental systems, but also about political and economic interests, conflicting values and faiths, differing assumptions about the future, and different judgments about resiliency in the face of the unexpected.

Research on Conflict Studies of environmental and technological conflict are a significant part of social research on conflict e. Issues of global environmental change have all the features characteristic of the most difficult technological controversies: awareness of human influence on the hazards, serious worst-case possibilities, the possibility of widespread and unintended side effects, delayed effects not easily attributable to specific causes, and lack of individual control over exposure National Research Council, b Social science can help illuminate the nature of environmental controversies and evaluate ways of managing them.

Social scientists interested in environmental policy have studied the conditions shaping and favoring the resolution of environmental controversies and the role of scientific, governmental, and mass media communication in the decision process e. Some have begun to consider the various ways environmental change might lead to conflicts with the potential for violence e. Social scientists specializing in conflict have developed generalizations that might be more thoroughly applied to environmental conflict.

For example, conflicts may be based mainly on ideology, interest, or understanding Aubert, ; Glenn et al. Defining an environ-. The nature of the relationship between the parties to a conflict can determine whether the conflict focuses on ideological positions e. And the behavior of the parties to a conflict depends on the pattern and relative strength of incentives to compete and to cooperate e. More research seems warranted to use existing knowledge about conflict to illuminate the ways social conflict may result from global environmental change.

This research would investigate the ways environmental changes may affect organized social groups and their resource bases and would hypothesize links between those effects and conflict. A first step is to construct an analytical framework for identifying the possible routes from particular environmental changes to particular types of conflict.

The framework of Homer-Dixon provides a start, for causes of violent conflict. Case analyses of past social conflicts can be used to assess hypotheses drawn from such analytic frameworks. Research on Conflict Resolution and Management Social scientists have also identified a number of approaches for resolving or managing policy disputes, some of which are beginning to be studied in the context of environmental conflicts.

These include mediation techniques intended to address the value dimension of environmental conflict e. The nature of technological conflicts suggests, however, that over the long-term, management is a more realistic goal than stable resolution. Recent work on risk communication is potentially relevant to social responses to global change because global change problems, like those to which that literature refers, are characterized by high levels of scientific uncertainty and great potential for conflict about social choices Covello et al.

This work suggests that institutions responsible for decisions about global change will also have to manage conflict. These institutions will need to provide accurate information, but should not expect information to resolve conflict. The institutions will need to make a place for the stakeholders to be represented from the earliest stages of the decision process, ensure openness in processes of policy decision, include mechanisms for the main actors to have access to relevant information from sources they trust, and use the conflicting perspectives and interpretations of current knowledge and uncertainty to inform the ongoing debate National Research Council, b; Stern, Research Needs Relatively little is known about the structure of particular conflicts about global change at the local, national, and international levels or about which means will be most effective in dealing with them.

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Therefore, we recommend increased empirical research, including both field studies and laboratory-simulation studies, to clarify the sources and structures of particular environmental conflicts and to test the efficacy of alternative techniques for their resolution and institutions for their management.

In Chapter 3 we presented cases to illustrate how human actions can contribute to the causes of global change. Here we present three cases to illustrate the human consequences of, and responses to, environmental change. Taken together, they show the importance of all the major human systems involved described later in the chapter and the ways that conflicts are played out and choices made within these systems.

As mentioned earlier, the most successful effort to date to address a global environmental problem by international agreement. This regime, in its current form, commits its members to phasing out the production and consumption of CFCs and a number of related chemicals by the year The regime represents the first concerted international effort to mitigate ''a global atmosphere problem before serious environmental impacts have been conclusively detected'' Morrisette, The political history of the ozone regime begins as a national issue in the United States and a handful of other Western countries in the early s, in connection with emissions from supersonic transport SST aircraft and then from aerosol spray cans Downing and Kates, ; Morrisette, Environmental groups organized opposition to the development of the SST and to the extensive use of aerosols.

Individual responses led to a sharp drop in sales of aerosol products Morrisette et al. The U. However, the EPA ruled that other uses of CFCs, such as in refrigeration, were both essential and lacked available substitutes. Ozone depletion emerged as a major international issue in the s. This occurred primarily as a result of initiatives by the United Nations Environment Programme Morrisette, and the actions of the international scientific community Haas, , with the support of the international environmental movement.

The Vienna convention of embodied an international consensus that ozone depletion was a serious environmental problem. However, there was no consensus on the specific steps that each nation should take. A number of events in and created a new sense of urgency about the depletion of stratospheric ozone. These included a rapid growth in demand for CFCs due to new industrial applications and the end of a global economic recession; important new studies by the World Meteorological Organization, the National Aeronautics and Space Administration, the Environmental Protection Agency EPA , and the United Nations Environment Programme; and, most important, the widely publicized.

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In January , EPA initiated a series of workshops designed to build an international scientific consensus supporting the need to control the use of CFCs. In the same year, DuPont announced that its scientists had determined that CFCs were the most likely cause of ozone depletion. These events persuaded American officials of the need for decisive international action. When negotiations on a protocol to the Vienna convention for controlling CFCs resumed in December , the United States adopted a firm position, calling for an international treaty not only freezing production of CFCs but also reducing production and consumption.

Following extensive and complex negotiations, the Europeans, whose earlier opposition to a cutback in production had prevented agreement in Vienna, moved closer to the U. They were persuaded to do so by three factors: the weight of scientific evidence, pressures from their own domestic environmental groups, and the fear that, in the absence of a treaty, the United States might take unilateral action to impose trade sanctions.

While compromises on several controversial points proved sufficient to gain Japanese and Soviet adherence, the major developing countries e. Only after the Montreal Protocol was signed did the full extent of ozone depletion became public: ozone depletion over Antarctica reached a historic high in , and the link to the release of CFCs became a matter of scientific consensus. DuPont responded by announcing that it planned to discontinue CFC production by the end of the century and, in March , countries called for the absolute elimination of production by the same date.

A resolution agreeing to totally phase out all production and consumption of CFCs by the year was adopted by 81 countries in May at the first governmental review of the Montreal Protocol. Taking advantage of this momentum, the parties to the Montreal Protocol, meeting at a review conference in London in June , were able to negotiate a series of strong amendments. These amendments accelerate the phaseout schedule for CFCs and halons and add methyl chloroform and carbon tetrachloride to the list of chemicals to be eliminated.

Equally important, the amendments establish an international fund to be used to assist developing countries in switching to substitutes for CFCs in the production of refrigerators and air conditioners. On the strength of this. Why was it possible to reach a broad international agreement restricting CFCs? Analysts have identified four important factors: an evolving scientific consensus; a high degree of public anxiety in developed countries about the risks associated with the continued use of CFCs, due in large measure to an association with skin cancer; the exercise of political muscle by the United States; and the availability of commercial substitutes for CFCs Haas, ; Morrisette, The last served the critical role of diminishing the opposition of the chemical industry to a phased reduction.

When DuPont, the producer of 25 percent of all CFCs, decided to develop substitutes, it "forced other CFC manufacturers to follow suit or risk losing market share" Haas, Haas adds that, because this issue could be resolved by a technical fix, it did not involve any hard choices and therefore may be unique in the annals of global environmental change. Another important influence in getting CFCs on political agendas may have been the efforts of the scientific community, which has been influential in drawing attention to other environmental problems Haas, Haas notes that it was initially a group of atmospheric physicists and chemists, most of whom worked in the United States, who attempted to place the issue of ozone depletion on the national and global environmental agendas, and that this community continued to press the issue throughout the s.

He argues that the speed of policy response in the United States may have been due to the "highly fragmented nature of American government and society [which] facilitates access of a strongly motivated group of technical experts" p. Thus, the access of a key group to policy debates at the national level may have influenced international action on CFCs. The history of the ozone regime illustrates a number of key variables that affect the likelihood of reaching similar agreements on other global environmental problems Sand, b; Benedick, Further studies are desirable to clarify how these variables interact:.

It also suggests that international agreements can be affected by the structures of national political systems, informal international communities, and markets that would be critically affected by agreement. Energy efficiency is probably the most widely accepted strategy for mitigating global warming.

The energy shocks of the s led to significant improvements in the energy productivity of Western industrialized economies. Between and , the United States reduced its energy intensity—the ratio of energy use to economic output—by 25 percent. The change was a sharp contrast to the record of the previous two decades and to most of the twentieth century. Between and , U. To the extent that energy intensity can continue to improve in the United States and other countries, energy efficiency can make an enormous contribution to mitigating global warming.

This section takes a closer look at how and why the change occurred in the United States and the implications for other countries. After increasing for 40 years, U. Although the reasons are not well understood, the secular decline in energy intensity since has been attributed to improved efficiency in energy conversion, a. The behavioral change after was largely due to the oil shocks of and , which rapidly altered energy prices, changed perceptions of the future price and availability of fossil fuels, and brought about policy changes.

Energy users made three effective kinds of responses U. Department of Energy, ; Schipper et al. First, they changed the way they operated energy-using equipment, curtailing heat and travel, and improving management, such as by tighter maintenance of furnaces. Such changes accounted for percent of national energy savings achieved in compared with the pre trend; estimates from U. Department of Energy, but are easily reversed when energy prices drop or incomes rise, as they did in the s. Second, energy users adopted more energy-efficient technology to provide the same service with less energy use, either by retrofitting existing equipment e.

These improvements were responsible for percent of total energy savings by Third, the mix of products and services in the economy changed. Demand fell sharply in energy-intensive industries, such as primary metals, relative to less energy-intensive industries; small cars got an increased share of the automobile market; and commercial airlines improved the match between aircraft size and demand on passenger routes.

Together, such shifts accounted for about percent of the energy savings achieved in Higher real energy prices are generally considered the most important single explanation for these responses International Energy Agency, ; U. Department of Energy, However, price is not the whole story. Although the two energy shocks of the period had very similar price trajectories, the effects on the economic productivity of energy differed markedly after the first two years see Figure For the first two years of each shock, real energy prices increased about 40 percent and energy productivity increased about 5 percent.

But over the longer-term, the second shock had much more effect than the first. A five-year price increase of about 45 percent in increased energy productivity 7 percent; a similar increase in increased energy productivity 18 percent. Moreover, the trend continued through several years of falling real energy prices. Why the different reactions to the two energy shocks? One explanation is perceptions: it took the second shock to get energy. Another is that the decision environment had changed by in ways that made it more likely the system would respond to price signals.

Government policies to promote energy-efficient technology and provide necessary information were in place by , making it easier for energy users to respond effec-. Moreover, U. Because these explanations reinforce each other, it is difficult to estimate their relative magnitude. The multiple explanations suggest that the price effect depends on other factors: technological change, policy choices, change in industrial structure, and information processing by energy users.

Since these factors can be changed independently of energy prices, it seems likely that with appropriate policies in place, energy intensity might have improved faster than it did, even in the apparently price-responsive period. Energy conservation policy in the United States has been predicated on the theory that government should intervene chiefly to correct so-called market imperfections such as the tendency of a supply system based on market prices to produce too little environmental quality because individual consumers cannot be charged for it and too little information on energy-efficient technologies and their costs.

The government can also intervene to mitigate regulatory and institutional barriers to the functioning of the price system. Following this theory, many U. Experience with these efforts shows that the market imperfection theory needs to be expanded to take into account deviations in energy users' behavior from conventional economic rationality. Such processes within individuals and small groups have impeded the effectiveness of conservation programs in the United States, but when they are taken into account, programs became much more effective. Evaluations of incentive and information programs show that, although they are sometimes very effective at increasing the pace of adoption of available technology, success varies greatly, even between nominally identical programs Berry, For instance, home energy rating systems reach between 2 and percent of homes, depending on the market Vine and Harris, , and utility companies offering exactly the same financial incentive program for home retrofits typically have participation rates that vary by a factor of 10 or more Stern et al.

Success depends on a number of features of implementation. A key is getting the attention of potential participants with appropriate marketing efforts, targeting of audiences, selection of trustworthy sources of information, and other basic principles of communication Berry, ; Ester and Winett, ; Stern et al. Getting people's attention appears to be the main barrier to the success of financial incentive programs for home retrofits, so that, paradoxically, "the stronger the financial incentive, the more the program's success depends on nonfinancial factors" Stern, Apparently, larger incentives ensure success among those who enter a program but do little to attract participants.

Finding the proper intermediary, such as a builder, manufacturer, designer, or lender, can also be critical. Home energy rating systems have been introduced most effectively with the active support of the building and lending industries Vine and Harris, , and residential conservation programs, especially in low-income areas, have often depended for success on involving highly trusted local organizations, such as churches and housing groups Stern et al. Involving consumers in program design can help fit a program to its audience and locale Stern and Aronson, Thus, conservation policies and programs played a part in the U.

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Improved policies and implementation, along with higher prices, are among the reasons energy productivity improved faster at the end of the period than at the beginning. These three factors act in conjunction, however. If, for example, energy prices fall or remain stable, lowering energy users' motivation to change, some policy instruments will become less effective than they were in The trends of the late s demonstrate this effect U.

The technological potential for improvements in energy productivity are huge National Academy of Sciences, b; National Research Council, a. However, the worldwide prospects for implementing technological changes, and therefore for mitigating the release of greenhouse gases, depends on the behavior of several human systems, including world markets for fossil fuels, national policies for economic and technological development and energy management, global social trends in government and the development of technology, and the behavior of individuals and communities.

The world energy price and supply picture will affect the spread of the Western improvements in energy productivity to other countries. Under conditions like those of the late s, with relatively low energy prices and stable supplies, sharp further improvements in installed energy efficiency are unlikely, even in the Western industrialized countries, without new policy initiatives. The price motive for efficiency is weak, policies that rely on that motive are undermined, and the lowered cost of energy is a spur to economic growth, particularly in energy-intensive sectors.

Given continuing population and economic growth, those conditions point to increases in energy use in the wealthy countries, although probably not at pre rates of increase. A new round of sharp price increases would cut energy use both by reducing economic activity and energy intensity, at least for a period. The world picture also depends greatly on the development paths of growing economies.

Industrialization is energy intensive, enough to have overcome the effects of the oil shocks in relatively wealthy countries, such as Greece and Portugal, that were still industrializing. Consumers' choices are also important. Where increased income goes into homes and durable possessions, as in Japan, energy productivity is more likely to be higher than where it goes into personal transportation, as in the United States, or into refrigerators or other energy-using appliances, as may become the case in China.

The future of the dissolving socialist bloc countries holds many uncertainties. Many of these countries have highly energy-intense economies and therefore seem to have room for improved energy efficiency given the rise of markets and more democratic control of policy. However, they lack finances to develop technology or implement incentive or information programs and need time to design and implement effective policies for local conditions. Much room exists for research and for pilot experiments with policy options as ways to reduce the uncertainty.

These and other human systems will determine the extent to which the Western experience with energy efficiency will proceed further or be repeated in other countries. The future will depend on the ways these systems interact in each country and on the ways national and local policies intervene in them. Intensification of the greenhouse effect is likely to alter rainfall patterns on a regional scale. As a rule, regions that receive increased rainfall are likely to benefit; decreased rainfall is the more serious concern.

The history of the human consequences of severe drought can be instructive about the variety of human consequences of, and responses to, unmitigated climatic change. The human role in causing drought in the Sahel region of sub-Saharan Africa is a matter of controversy. Throughout the modern history of drought-famine association in the region, there has been a tendency to interpret extreme events as indicators of trends and to attribute the presumed trends to human mismanagement of the local environment.

In fact, Sahelian droughts have been recurrent events. The droughts of the s and s were preceded by several others in this century, one of which, in , resulted in intense famine with high mortality. The controversy over the human role in causing Sahelian drought revived with the drought of The prevailing view was that desertification was an anthropogenic process reflecting deforestation, overgrazing, overfarming, burning, and mismanaged irrigation resulting in salinization of soil and water.

Lack of good data is a major obstacle to understanding the causes of Sahelian drought. Although some evidence supports the orthodox view, some recent research using remote sensing, field measurements, and intensive investigations of small areas has called that view into question. Observable ecological changes are less significant than had been supposed and correlate better with rainfall records than with land management Mortimore, The consequences of Sahelian droughts in this century have depended on the ability of indigenous systems of livelihood to.

During the century, these indigenous systems have undergone continual change, first as a result of policies of colonial powers, and later in response to postwar development policies promoting ''modernization'' and further integration into the global economy. There are competing views of the effects of these century-long trends in political economy on the ability of local populations to withstand drought. In one view, the main results were increased dependency and vulnerability; in the other, vulnerability decreased because of improved availability of medical care, famine relief, and a national infrastructure that allowed for easier.

The three major droughts of the century, in , in , and in the s, have had different effects on the lives and livelihoods of the local populations. The drought, which was of comparable severity to the drought of the s, appears to have produced greater increases in mortality; its effects on malnutrition and on the social fabric are harder to determine Kates, The knowledge base is better for comparing the droughts of the s and s. Population continued to increase at up to 3 percent annually, forests continued to be cut for fuel and farming, and other forms of resource exploitation probably continued at about the previous rates.

Grazing pressure fell, owing to animal mortality but, by the s, cattle holdings had recovered to 60 percent of predrought levels in some areas, and small livestock probably recovered more. On balance, the human demands on the local environment were at least as severe as before the drought. The drought of the s was as severe as the previous one. Annual rainfall in was of the same order as in , and in some areas of the Western Sahel, less. Crop failures and pasture shortages were equally serious.

Yet famine did not occur on the same scale, and animal mortality was lower. Possibly food aid was earlier and better in some countries, but in northern Nigeria, where food aid was not a major factor in either period, social distress was noticeably less marked in the s, even in the worst affected areas.

What explains the relatively low human cost of the s drought? It was not the response of the affected governments. Political officials were taken by surprise about equally by both droughts. The people most experienced in surviving failures of agricultural production and managing the environment were those living in the affected areas, but this group had little influence on policy.

Of the several political interests concerned with the drought prob-. Consequently, proposals for new technologies for coping with the drought failed to take indigenous technologies and management systems seriously, and measures to strengthen the poor—for instance by insurance, improved access to resources, alternative job opportunities, and price supports—were rarely considered or given high priority.

A key to drought response appears to have been the role of indigenous forms of land use and response to food shortage. It is possible to distinguish two strategies of land use for areas like the Sahel that face recurrent drought or a long-term threat of declining rainfall. One strategy—maladaptive in the long run—is characterized by deforestation and overcultivation and leads to land degradation, decreases in productivity, and, in the event of drought, short-term collapse. Another—adaptive in the long run—is based on flexible land use, economic diversification, integrated agroforestry-livestock management, and intensive use of wetlands.

This pattern tends to generate sustainable, intensive systems and is resilient in the face of drought. Indigenous strategies of response to acute food shortage apparently enabled the Sahelian populations to survive notwithstanding the tardiness, inadequate scale, and maladministration of most relief programs. These strategies, which relied on economic diversification, such as using labor in urban areas to supplement agricultural income, have evolved in an environment of climatic uncertainty and confer a degree of short-term resiliency.

Their future evolution is hard to predict. Continued integration into the world economy may improve roads and other infrastructure, thus enabling diversification; it may also increase pressure for development of cash crops and thus hasten land degradation. The ability of indigenous systems of land use and crisis management to cut the link between drought and famine depends on various factors that sustain the indigenous systems.

These include diversity of economic opportunities, absence of war, and appropriate national and international policies on migration. Critical variables include the development of infrastructure and the set of national policies governing access to land, trees, and water. The social distribution of wealth, particularly secure rights of individual or community access to natural resources, determines the extent of human vulnerability to drought. Although some impor-. Ruling and military elites, professionals in the civil service, traders especially in grain , capitalistic farmers, livestock owners, wood fuel exploiters, and small farmers and herders all have separate and distinct interests in the outcome, and most of these interests do not accord high priority to sustainable environmental management or drought preparedness.

Although not enough is known to forecast the consequences of future Sahelian droughts, two alternative scenarios can be imagined. In the doomsday scenario, increasing numbers of people generate cumulative environmental degradation overcutting of woodland, overcultivation of soils, overgrazing of pastures, and overirrigating and possibly overuse of water , suffer increasing food scarcities as available grain per capita declines, and either starve in huge numbers or migrate in distress to other areas where they become permanently dependent on international relief.

In the optimistic scenario, farming systems intensify using an increased labor supply, productivity of the land is raised, sustainable agroforestry-with livestock systems are extended, and household income sources are diversified and slowly shifted via the market and short-term mobility away from agriculture and toward other economic sectors. The experience of the s and s suggests that the optimistic scenario is a plausible alternative, given the right policy environment. Its success depends on increased recognition of the potential of indigenous sociocultural systems of land use and household strategies of economic diversification to increase resilience, and on policies that promote resource access and support those local social systems.

The consequences of future droughts may also depend on rates of urbanization, growth of the urban informal sector, and capital investment in better favored rural areas. The present policies of governments and international organizations in the Sahel can create conditions that promote or impede the ability of indigenous systems to respond and thus determine the human consequences of future drought. This section distinguishes seven human systems that may be affected by, and respond to, global change: individual perception, judgment, and action; markets; sociocultural systems; organized action at the subnational level; national policy; international co-.

It briefly surveys current knowledge and ignorance about the responses of each system and the relationships between them and identifies broad areas in which additional research is needed. It also outlines particular research activities and needs within these areas. The human consequences of global change begin with the individual.

Individuals notice the effects of change and either make adjustments or not. Individual behavior is critical in three quite distinct ways: individual judgments and choices mediate responses in all human systems because decision makers begin with inputs from individuals, whether themselves or their advisers. The consequences of global change often depend on the aggregation of the uncoordinated actions of large numbers of individuals.

And individual behavior can be organized to influence collective and political responses. Responses to global changes presuppose assessments of "what is happening, what the possible effects are and how well one likes them" Fischhoff and Furby, Knowledge about human judgment and decision is therefore relevant to understanding responses to global change. Normative decision principles, such as those of cost-benefit analysis or mathematical decision theory, are limited in their usefulness by the fallibility of the individuals who try to implement them Fischhoff, ; they are even more imperfect for estimating the behavior of people who are not trying Fischhoff et al.

Past research on human judgment and decision has clarified many differences between decision theory and actual decision making Kahneman et al. Behavioral decision research demonstrates that most people have difficulty comprehending the very low probabilities assigned to environmental disasters Slovic et al. Moreover, it is difficult or impossible to understand unprecedented events and therefore to make wise choices between mitigating them and adapting to them.

One result is that lay people frequently perceive environmental hazards differently from specialists Saarinen, ; Fischhoff and Furby, ; Gould et al. Little direct knowledge exists, however, on perceptions of climate, climate change, or other aspects of global change Whyte, ; Kempton, ; Doble et al.

Behavioral research also raises questions about expert judgment. Expert analyses, such as represented in general circulation models of climate, inevitably rely on judgment, and judgment becomes more unreliable when the models move into a future different from any past experience. Faith in expert judgments rests on the analysts' success in identifying all the relevant variables and measuring them and their interrelations. Psychological research suggests that people, including technical experts, "have limited ability to recognize the assumptions upon which their judgments are based, appraise the completeness of their problem representations, or assess the limits of their own knowledge.

Typically, their inability encourages overconfidence" Fischhoff et al. Overconfidence is most likely to affect expert analysts when they lack experience testing their predictions against reality—an inevitable characteristic of predictions about unprecedented events Fischhoff, Other kinds of systematic error may also affect experts. For instance, in water resource management and other fields in which average climate parameters are used as a basis for decision, experts seem to exhibit a "stability bias," a tendency to underestimate the likelihood of extreme events Riebsame, ; Morrisette, Careful analysts also sometimes overlook or underestimate the likelihood of some possible combinations of events, as they did in a famous assessment of the likelihood of nuclear power plant failure in the s Nuclear Regulatory Commission, Little is known about how individuals or groups formulate alternative action plans when faced with a problem, such as responding to a global environmental change.

In particular, little is known about what facilitates or impedes creative generation of options, or how vested interest or attachment to the status quo may blind individuals or groups to available options. Research Needs Research on what and how nonexperts think about particular global environmental problems can help estimate how individuals will respond to new information about the global. This research should address particular beliefs about global change as well as how people evaluate probabilistic and uncertain information and how they combine multiple bits of information from experts, mass media accounts, and personal experience e.

Such research will require both intensive methods of interaction with informants and survey methods. Research effort should also be devoted to studying the expert judgment of environmental analysts about global change. This research should address such questions as: Does professional training encourage or discourage particular misperceptions?

Does it lead purportedly independent experts to share common preconceptions? How well do the experts understand the limits of their knowledge? Do estimates of the human effects of global change take into account feedbacks among human systems? In analyses of possible responses, what responses are likely to be omitted? To whom do experts turn for analyses of feasibility of responses? What implicit assumptions about human behavior guide the analyses?

With preliminary answers to such questions, it is possible to estimate the sensitivity of analyses to variables that affect expert judgment and therefore to make better informed interpretations of these judgments. The consequences of global environmental change often depend on the aggregated responses of very large numbers of individuals.

The example of U. Action to block UV-B radiation from the skin of a billion light-skinned people would similarly take many discrete actions by each of them. Financial considerations motivate action, but structural constraints limit action for instance, not owning the home one would like to insulate ; personal attitudes and values increase the likelihood of taking actions that fit the attitudes, subject to the other constraints; specific knowledge.

Knowledge has been developed about the conditions under which individuals respond favorably to information Ester and Winett, ; Dennis et al. Research Needs At least three kinds of research should be pursued further to improve understanding of how individual behavior may be significant in response to global change.

First is empirical research on the actual responsiveness of behavior to interventions believed to affect it. Energy conservation programs have often produced less than the predicted effects—but as already noted, the responses have been highly variable. For studying possible interventions to mitigate or adapt to global change, pilot studies and controlled evaluation research are particularly important for a discussion of issues of method in the energy conservation context, see Stern et al. Second, new research is warranted to determine the relative contributions and interactions of the various influences on particular individual behaviors implicated in global change e.

This research should be interdisciplinary because, in most instances, behavior is jointly determined by technical, economic, psychological, and social variables in ways that are likely to differ as a function of the behavior and the societal context. Third, research should be conducted to build an improved interface between behavioral studies of resource use and formal models, which are guided mainly by economic assumptions.

Empirical analysis of the behavioral processes underlying descriptive categories such as price elasticity, implicit discount rate, and response lag is likely to add to understanding of human responses to price stimuli and government intervention, and also to encourage needed dialogue between economically and psychologically oriented analysts of consumer behavior Stern, , Individuals, appropriately mobilized, can be powerful actors at the community and national levels.

Individual perception and judgment determines support for social movements, such as the. Those actions, in turn, influence individual behavior both directly and through their effects on markets. Individual reactions, in the aggregate, determine the public acceptability of policy alternatives being considered for response. And secular changes in individual attitudes and values, such as about the importance of material goods to human well-being, may have great effects on the long-term response to global change. Past research has investigated the correlates of environmental concern and related attitudes e.

Such attitudes have been strong and persistent in many countries since the s. Other research has been devoted to the rise of the environmental movement and to its objectives and tactics see below. Research Needs There are important gaps in the literature. New research should carefully assess alternative hypotheses about the links between individuals' values and attitudes and their representation in the activities of environmental movement groups and other institutions involved in response to global change.

For instance, the view that environmental organizations reflect widespread attitudes should be tested in the global context against other views, for instance that social movement activists act as entrepreneurs, with their own interests separate from those of the public they claim to represent e. Future research should also address the bases of environmental concern. Such concern may derive from a new way of thinking about the relationships of humanity to the planet e. Outside the U. For instance, in several Soviet republics, the environmental movement of the late s expressed demands for autonomy by smaller nationality groups against the dominant Russians.

On another dimension, environmental concern may derive from personal experience or secondhand accounts in the mass media. The source of concern may determine the conditions under which people become aroused about a global change or recep-.

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  6. Earth's temperature is a balancing act.

The determinants of concern are likely to vary with the environmental problem, the country, and characteristics of the individual, so the research should be comparative between countries and environmental problems of different kinds. One of the most likely consequences of global change will be effects on the prices of important commodities and factors of economic production in local and world markets. As a result, uncoordinated human responses will be affected greatly by markets. According to economic theory, producers and consumers respond to changing relative incomes, prices, and external constraints, so that, if the market signals are allowed to reach individuals and market prices include all the social costs and benefits of individual actions, the responses will be relatively rapid and efficient.

Markets allow for many forms of uncoordinated adjustment, as the example of climate change illustrates. People may rapidly alter patterns of consumption e. Over the longer run, societies may respond, in the case of unfavorable climatic developments, with the migration of capital and labor to areas of more hospitable climates. Structures tend to retreat from the advancing sea, people tend to migrate from unpleasant climates, and agricultural, sylvan, and industrial capital tend to migrate away from lands that lose their comparative advantage.

In addition, technology may change, particularly in climate-sensitive sectors such as agriculture and building. However, the conditions that economic theory specifies for efficient adjustment are not generally met in the case of the global environment Baumol and Oates, In three important respects, existing markets do not provide the right signals in the form of prices and incomes of social scarcities and values. And in addition, as already noted, the participants in markets do not always behave as strict rules of economic rationality predict.

Environmental externalities of economic activity, that is, effects experienced by those not directly involved in economic transactions, are not priced in markets today. Someone who emits a ton of carbon into the atmosphere may produce great damage to the future climate but does not pay for the damage: effects that. Similar problems arise with the externalities of deforestation, CFC emissions, and other environmental problems.

Economic theory recognizes that when there are significant externalities, uncoordinated responses will be inappropriate because the market does not transmit the right signals. An additional problem concerns making tradeoffs when each response option produces different externalities Fischhoff et al. The market mechanism is overridden at times, either by political systems such as when countries set the prices of oil or coal well below or above world market levels ; or because custom and tradition determine property rights in a way that precludes the emergence of markets, as in the case of water allocation in the western United States.

In such cases, individuals are either not faced with prices at all or are faced with prices unrepresentative of true social scarcities, and their uncoordinated behavior will not achieve the rapid and efficient adjustments characteristic of free markets. Discount rates in markets, such as interest rates, reflect a social time preference for the present over the future that does not correspond to social valuation of the distant future reflected in concern about problems of global change Lind, For events a century in the future, a discount rate that is, say, 3 percent per annum higher than true social preference implies that the future events are valued at only one-twentieth that is, 1.

Market interest rates may be too high to reflect this generation's concerns about the future of the environment; vigorous debate exists about whether the concept of discounting is even moral when human life is at stake MacLean, Uncoordinated decisions following such a discount rate undervalue future threats and opportunities. Economic theory suggests prescriptions for government action when market signals do not correspond to social values. The goal usually considered most important is to get the environmental impacts reliably translated into the price and income signals that will induce private adaptation.

But it is difficult to arrive at the "correct" prices because so many of the impacts of global change are unknown or uncertain and because the appropriate values of future events are unlikely to be the same from all generational vantage points and resource endowments Lind, ; Pearce and Turner, Economists have suggested some approaches to the problem of developing well-functioning markets to guide responses to global.

Theory suggests that governments intervene with policies that meet at least one of these criteria: 1 they have such long lead times that they must be undertaken now to be effective; 2 they are likely to be economical even in the absence of global change; or 3 the penalty from waiting a decade or two to undertake the policy is extremely high. These criteria suggest four kinds of intervention, which we note here.

Government may encourage quasi-market mechanisms before shortages occur. For example, to ensure that water will be efficiently allocated if climate change affects its availability, governments might introduce general allocational devices, such as auctions, to dispatch water to the highest-value uses. The same approach might be applied to allocate land use near sea coasts and in flood plains and to control pollution by auctioning pollution rights. Governments might also support systems of risk-adjusted insurance for flood plains or hurricanes or international climate insurance.

These quasi-market mechanisms have both the advantages and the disadvantages of the market. They make allocations efficiently but tend to undersupply goods needed by those who do not participate effectively in the markets, such as people outside the geographical boundaries of a quasi-market, who may receive polluted air or salinated water. Government may support research and development on inexpensive and reliable ways of slowing or adapting to global change. Research on adaptation is undersupplied by markets because inventors cannot capture the full fruits of their inventions.

Research on mitigation technologies that will slow global changes are even more seriously undersupplied in markets, because not only can inventors not collect the fruits of their efforts, but also the fruits, such as preservation of climate, are unpriced or underpriced in the market. International agreements may provide for international adaptation strategies, such as improved international markets, which allow migration of labor and capital over a greater geographical range than national markets.

Governments may promote needed knowledge and collect and distribute data about global change, to enable rational response. It is difficult for people to mitigate or adapt if they do not understand what is happening or the costs of the available responses and of inaction; costs of adaptation will be reduced to the extent that managers, diplomats, and voters are well informed about well-established scientific results. Research Needs Although the above market-oriented response strategies are strongly supported by economic theory, knowledge is weak about how they may be effectively implemented.

Three lines of research into markets can add to understanding of the available response strategies. First, empirical studies are needed of the implementation of quasi-market mechanisms for adaptation to global change, to determine how particular mechanisms work in particular social and political systems. For instance, systems for auctioning emission rights can be made infeasible by political opposition, subverted by fraud, undermined by political decisions, or otherwise altered from their theoretically pure operation Tietenberg, , explains the principle in the case of local air pollution; application to global change would be more difficult.

Warmer periods coincide with periods of relatively high CO 2 concentrations. Increases over the past half century are shown in the Recent Role section. Source: Based on data appearing in NRC Climate feedbacks amplify or reduce direct warming and cooling effects. Feedbacks that amplify changes are called positive feedbacks. Feedbacks that counteract changes are called negative feedbacks. Feedbacks are associated with changes in surface reflectivity, clouds, water vapor, and the carbon cycle. Water vapor appears to cause the most important positive feedback.

As Earth warms, the rate of evaporation and the ability of air to hold water vapor both rise, increasing the amount of water vapor in the air. Because water vapor is a greenhouse gas, this leads to further warming. The melting of Arctic sea ice is another example of a positive climate feedback. As temperatures rise, sea ice retreats. The loss of ice exposes the underlying sea surface, which is darker and absorbs more sunlight than ice, increasing the total amount of warming. Some types of clouds cause a negative feedback. Warming temperatures can increase the amount or reflectivity of these clouds, reflecting more sunlight back into space, cooling the surface of the planet.

Other types of clouds, however, contribute a positive feedback. For example, as temperatures warm:. These changes lead to higher concentrations of atmospheric GHGs and contribute to increased warming. The primary human activity affecting the amount and rate of climate change is greenhouse gas emissions from the burning of fossil fuels.

The sources and recent trends of these gases are detailed below. Carbon dioxide is the primary greenhouse gas that is contributing to recent climate change. Human activities, such as the burning of fossil fuels and changes in land use, release large amounts of CO 2 , causing concentrations in the atmosphere to rise. The monthly average concentration at Mauna Loa now exceeds ppmv for the first time in human history. Methane is produced through both natural and human activities.

For example, natural wetlands, agricultural activities, and fossil fuel extraction and transport all emit CH 4. In recent decades, the rate of increase has slowed considerably. Nitrous oxide is produced through natural and human activities, mainly through agricultural activities and natural biological processes.

Fuel burning and some other processes also create N 2 O. Overall, N 2 O concentrations have increased more rapidly during the past century than at any time in the past 22, years. To learn more about actions that can reduce these emissions, see What You Can Do. Particles and aerosols in the atmosphere can also affect climate. Human activities such as burning fossil fuels and biomass contribute to emissions of these substances, although some aerosols also come from natural sources such as volcanoes and marine plankton. It has followed its natural year cycle of small ups and downs, but with no net increase bottom.

Over the same period, global temperature has risen markedly top. Climate is influenced by natural changes that affect how much solar energy reaches Earth. The intensity of the sunlight can cause either warming during periods of stronger solar intensity or cooling during periods of weaker solar intensity. Changes in solar energy continue to affect climate. When sunlight reaches Earth, it can be reflected or absorbed. Light-colored objects and surfaces, like snow and clouds, tend to reflect most sunlight, while darker objects and surfaces, like the ocean, forests, or soil, tend to absorb more sunlight.

The term albedo refers to the amount of solar radiation reflected from an object or surface, often expressed as a percentage. Reflectivity is also affected by aerosols. Aerosols are small particles or liquid droplets in the atmosphere that can absorb or reflect sunlight. Unlike greenhouse gases, the climate effects of aerosols vary depending on what they are made of and where they are emitted. Those aerosols that reflect sunlight, such as particles from volcanic eruptions or sulfur emissions from burning coal, have a cooling effect.

Those that absorb sunlight, such as black carbon a part of soot , have a warming effect. Volcanoes have played a noticeable role in climate. Volcanic particles that reach the upper atmosphere can reflect enough sunlight back to space to cool the surface of the planet by a few tenths of a degree for several years. Volcanic particles from a single eruption do not produce long-term change because they remain in the atmosphere for a much shorter time than GHGs. Processes such as deforestation, reforestation, desertification, and urbanization often contribute to changes in climate in the places they occur.

These effects may be significant regionally, but are smaller when averaged over the entire globe. In addition, human activities have generally increased the number of aerosol particles in the atmosphere. Overall, human-generated aerosols have a net cooling effect offsetting about one-third of the total warming effect associated with human greenhouse gas emissions.

Reductions in overall aerosol emissions can therefore lead to more warming.