Special Report — RFF Workshop on Greenhouse Warming

June of 1988 was an appropriate time for the RFF Workshop on Controlling and Adapting to Greenhouse Warming. The extreme heat of the summer of '88 had not yet descended on the Capitol or the nation and the drought in the Northern Plains and Corn Belt had not yet reached its full ferocity. Later in the summer tremendous attention was generated by the unusual heat, the severe drought, and a statement—made before Congress by a prominent scientist from the National Aeronautics and Space Administration—interpreted by the media as indicating 99 percent certainty that the greenhouse effect had in fact arrived. Had the RFF workshop been held later in the summer of '88, careful, calm deliberation might have been more difficult to sustain.

More than 150 people filled the National Academy of Sciences' lecture room to hear workshop papers of four kinds. The first papers provided a scientific briefing on the nature of the greenhouse effect, how it is linked with fossil fuel combustion and land use changes, predictions of climatic change and sea-level rise that may follow greenhouse warming, and the degree of certainty that scientists associate with these predictions. RFF economists joined with natural scientists to present another group of papers which examined the possible effects of greenhouse warming on agriculture, forestry, unmanaged ecosystems, and water resources. The policy and economic implications of controlling global warming and adapting to its possible effects were examined by other RFF authors in a third group of papers and by a special panel. The prospect of global warming was examined from the perspective of the developing nations and in the general context of global-scale environmental changes that now appear to be occurring. Space permits us to report on only a few of the papers and findings presented at the workshop. A full proceedings volume is being prepared for publication by RFF in early 1989.

Scientific background

Stephen Schneider of the National Center for Atmospheric Research and Norman Rosenberg of RFF presented a paper on the scientific basis of the greenhouse-effect issue. Were it not for water vapor, carbon dioxide (CO2), and a few other atmospheric gases that are transparent to incoming solar radiation but effective absorbers of outgoing infrared (thermal) radiation (the greenhouse effect), the world we live in would be about 60°F colder than it now is.

No one is concerned that a greenhouse effect exists; indeed, without it life on earth as we know it would be impossible. The concern, rather, is that human activities are adding CO, and other greenhouse gases (methane, nitrous oxide, the chlorofluorocarbons, and ozone produced by air pollution in the lower layers of the atmosphere) to the atmosphere, with the probable result that the climate will become warmer and change in other ways. CO2 concentration is expected to reach double its pre industrial concentration (approximately 280 parts per million) late in the next century. In about fifty years enough CO2 and other greenhouse gases may have accumulated to cause the same warming as would a CO2 doubling.

We cannot determine the precise amount of warming nor the regional patterns of climate change that may have occurred as a result of trace gases already accumulated in the atmosphere, since climate is so naturally variable or "noisy." Most atmospheric scientists now agree that if current trends of greenhouse gas emissions continue, and certainly if they accelerate, the signal of global warming may soon emerge from that noise; but still our scientific tools do not permit prediction of the precise amount of warming or how its effects will be distributed regionally. However, if warming occurs, cloudiness, windiness, humidity, precipitation, and evaporation will change, as will their interseasonal, interannual, and spatial variances.

Another factor to consider is the direct effect of CO2 on plant growth. Photosynthesis increases in most plants exposed to higher concentrations of CO2, and transpiration (water use) decreases in virtually all species. Effectively, the water use efficiency—the amount of vegetation produced per unit of water consumed—is improved. These responses have been demonstrated in greenhouse studies, but we do not yet know whether they will occur (or are already occurring) in the open field and forest.

Some impacts

Sea-level rise is one of the most likely effects of a future greenhouse warming. Sea level will increase because of thermal expansion of ocean water and because some sea ice and glaciers will melt. At the RFF workshop, Gjerrit Hekstra, an official of the Netherlands Ministry of Housing, Physical Planning and Environment, spoke of the consequences of a sea-level rise of 50 to 100 centimeters occurring in the next century. Changes in meteorological conditions—especially wind direction and wind force—by increasing or diminishing storm surges may turn out to be more consequential than sea-level rise per se. In Europe (the North Sea, in particular), coastal defenses already typically stand 16 to 19 meters above mean sea level. In areas that are currently unprotected or inadequately protected and where low-lying areas are densely populated (Bangladesh, parts of Indonesia, Malaysia, the Nile delta), the risks to life would be far greater and the wherewithal to provide defense more limited than in more affluent areas.

Other problems that may be created by rising sea level include coastal regression due to erosion of beaches, dune coasts, and barrier islands. Sediment transport from inland will be altered in river deltas and estuaries. Salt water will intrude through river mouths and canals into groundwater and agricultural fields, posing major economic threats.

Agriculture

In their workshop paper, Martin Parry from the University of Birmingham, England, and William Easterling and Pierre Crosson of RFF expressed certainty that if the climate changes, there will be important consequences for agriculture. With or without climate change, slower population growth and a declining proportion of income spent for food suggest that world demand for food and fiber will increase more slowly in the next fifty to seventy-five years than it did in the past forty years.

Climate change apart, advances in technology should expand global agricultural capacity in pace with increases in world demand. Climate change of the magnitude predicted to occur some fifty years from now in response to an effective CO2 doubling would not, they predict, significantly alter this generally favorable assessment. However, climate change leads to increased frequency, duration, and regional extent of extreme events such as drought, flood, heat waves, and the like. Short-term shocks to world agricultural production and prices (not unlike the impacts of droughts in the Soviet Union in the early 1970s or in North America in 1988) could occur more frequently.

Over the longer term, regional comparative advantage in agriculture is likely to become more diffuse as more countries endowed with abundant natural resources, such as Brazil and Argentina, become major actors in world agriculture. Climate change may reinforce these shifts in some regions and weaken them in others.

Developing strategies for adapting agriculture and other resource sectors as well to these uncertain future conditions likely will require increased investment in both natural science and social science research and shifts in research priorities.

In their workshop paper, Roger Sedjo of RFF and Allen Solomon of the International Institute for Applied Systems Analysis concentrated on the possible impacts of greenhouse warming on forests. The location and species composition of forests are very sensitive to climate conditions. For example, about 11,000 years ago when glacial ice in North America was at its most southward position, the center of concentration of oak was in eastern North Carolina, and spruce forests grew as far south as Virginia. Following the retreat of the ice both species moved northward. Today oak grows successfully near the Canadian border and spruce is concentrated in central Canada, reaching to the tundra. Spruce might advance even further into the tundra in response to greenhouse warming, but the boreal (northern) forests likely would lose ground at their southern margins to other tree species or to grasses.

Sedjo and Solomon also focused on forests as a potential sink for absorbing a considerable amount of the CO2 that is now emitted into the atmosphere by fossil fuel combustion and because of land use changes such as deforestation. A sufficiently large increase in the forest biomass, achievable by increasing the numbers of trees, their size, or the area of land covered by forests, or by some combination of these, could increase the sink for atmospheric CO2 enough to delay the onset of global warming by perhaps three to five decades. This would buy time for society to develop energy alternatives to fossil fuels, to find other ways to sequester carbon before it is emitted into the atmosphere, and to develop successful adaptations to whatever degree of global warming would not be prevented by these measures.

Expansion or reduction?

Spontaneous expansion of forests due to global warming is one possibility, but the net effect of climate change could also be a reduction in total forested area. The amount of carbon stored in existing forests might be increased by management methods that lead to bigger trees, but there may be few opportunities to employ this approach. The planting of new forests may be more feasible technically. However, to avoid further increases in atmospheric CO2 concentration while yet allowing for continued emission of carbon at current rates would require plantations of at least 465 million hectares (4.65 million square kilometers) of new forest—an area about two-thirds the size of the contiguous United States. Establishment and land acquisition costs for plantations on this scale would be at least $375 billion in a temperate climate. In the tropics the cost would be about $190 billion because cheaper land could be used. The annual yield of wood from such an area of forest when mature would be four times greater than is now harvested from all of the world's forests combined. Placing all that wood on world markets for lumber, paper, and other timber products would severely disrupt them. If the wood were harvested but held in inventory, market disruption could be avoided, but the costs of harvest, transport, and inventorying could come to an additional $300 billion.

Sedjo and Solomon suggest that, as a way around these costly alternatives, the wood could be used as an energy substitute for fossil fuels in generation of electricity. Burning the wood would not increase atmospheric concentrations of CO2 so long as the larger forest biomass were maintained by replanting trees after harvest and burning.

Sedjo and Solomon did not advance plantation forests as a solution to the CO2 problem. They suggested, however, that it deserves a place among the alternatives which the global community sooner or later will have to consider.

These examples of possible effects of greenhouse warming on natural resources and possible responses to these effects illustrate the complexity and difficulty of determining whether, how, and when to engage in activities that lead either to controlling warming or adapting to it.

Control

In his workshop paper, Pierre Crosson addressed the issue of control by asking how the global community might determine the maximum socially acceptable amount of greenhouse warming and then forge a consensus around measures to hold warming within that limit. Crosson argued that the maximum acceptable warming should be that at which the social costs to the global community of additional warming would equal the cost of preventing it. The principle is easily stated, but formidably difficult to implement. Although the intercountry distribution of the costs of warming, and of controlling it, are highly uncertain, current research suggests that the distribution would be quite uneven. Some countries could conclude that the costs to them of continued warming would be small, or that they might even benefit, while other countries might see themselves as heavy losers.

The geographic distribution of costs of controlling warming also are likely to be uneven. Since reduction in global consumption of fossil fuels inevitably would be a main instrument of control, the costs of control likely would fall more heavily on countries rich in those resources than on those less well endowed.

The uneven regional distribution of the costs of control would be unimportant if the costs were known to be low. Some energy analysts have argued that in fact the costs are low, at least so far as control of CO2 emissions is concerned. The argument is that global use of fossil fuel could be cut in half in a few decades, without sacrifice of world income growth, by a global shift to more energy-efficient end-use technologies, for example, more fuel-efficient cars.

If the argument is correct, there should be little difficulty in forging an agreement among countries to achieve sharp reductions in fossil fuel use and, therefore, in CO2 emissions. It is fair to say, however, that not many governments are now persuaded by the argument. Until a majority are, including those rich in fossil fuel resources, the costs of swift reductions in fossil fuel use likely will be regarded as high, and the uneven regional distribution of the costs will function as a barrier to a global agreement to control warming.

The unequal distribution of income among countries also is a likely barrier to agreement. All countries may agree that fairness to future generations requires that global warming must eventually be controlled. However, if the costs of control are perceived to be high, then the sooner control is achieved, the heavier the cost burden shouldered by our generation and the lighter that borne by later ones. A decision about how much warming is acceptable thus involves judgments about what constitutes a fair intergenerational sharing of the costs of controlling warming and of not controlling it. Poorer countries may want to shift more of the costs to later generations, rich countries more to ours.

These different perceptions about the regional distribution of the costs of warming, and of controlling it, and about fairness in the intergenerational sharing of the costs, assure that getting a global consensus about acceptable limits to warming will be difficult. The thrust of the discussion at the RFF workshop seemed to be that agreement on a warm-ing limit and on measures to enforce it would be more difficult to achieve than was the 1987 Montreal protocol on control of chlorofluorocarbons.

Role of economics

Casting the limits-to-warming issue as one of balancing incremental costs of warming with incremental costs of control evoked much discussion at the RFF workshop about the role of economics in analysis of climate change consequences and policies. Some participants argued that the tools of economics, particularly cost-benefit analysis, are of very limited usefulness because many of the costs of climate change are not quantifiable, some perhaps not even in principle. Moreover, in this argument, economics is inappropriate because, through discounting, it implies that nearer-term costs and benefits are more important than those occurring in the longer term. This unfairly discriminates against future generations. Some participants—at least one—went further, asserting that halting warming, like national defense, is an imperative that must be obeyed, "whatever the cost."

Those who defended economics—and only economists did—did not dispute the inappropriateness for climate change issues of cost-benefit analysis and discounting, as traditionally applied, for example, in valuation of an irrigation project. They insisted, however, that the concepts of costs and benefits, broadly construed to include social and political dimensions as well as unpriced values, such as species preservation, inevitably come into play when policy decisions are made about what, if anything, to do about global warming. Cost-benefit analysis in this broad sense is simply an attempt to think, and act, rationally. And, the counterargument continued, discounting of future costs and benefits also inevitably is done when countries make judgments about the intergenerational fairness of alternative intertemporal distributions of the costs of controlling warming and of not controlling it. As for the national defense analogy, it is obvious that all countries try to determine trade-offs between defense and other national objectives when deciding how to allocate national resources. That is, countries, however imperfectly, apply economic logic to national defense spending as they do to other kinds of spending.

No consensus was reached at the RFF workshop on these issues, nor was it clear that progress was made toward a consensus. It was clear at the end, however, that narrowing the intellectual gap between economists and non-economists would contribute to more fruitful analysis of global warming consequences and related policy issues.

The exposition of facts and uncertainties of the greenhouse issue, the assessment of its possible effects on natural resources and possible responses to these effects, and the evaluation of the logic and framework needed for determining whether, how, and when to abate or adapt will, we hope, have been illuminated by the presentations at the RFF workshop.