To provide the reader with an overview, this part of the report begins by stating its findings in a few pages. It next states the recommendations that arise from the findings. Then it discusses fully the issues, evidence, and reasoning about impact and adaptation that underlie those findings and recommendations.
Climate Change is One of Many Changes
The effort and resources that we spend on understanding, predicting, adapting to, and mitigating climate change could be spent on other beneficial acts. Therefore, how much we spend on climate change depends on its projected importance ranked against other problems we face. The rank of climate change as a policy issue during the next century will be influenced by the speed and direction of climate change and the sensitivity of humanity and nature generally to them. Moreover, it is also influenced by the speed and direction of all the other changes, such as changes in population, land use, environment, wealth, and the susceptibilities of humanity and nature to climate and to all the other changes. How much of humanity's limited attention, talent, and money should we concentrate on climate change rather than epidemics and drugs, shelter and food, art and arms? Other things being equal, it is wise to invest more to deal with the changes with the highest rank, provided that those investments can significantly reduce the hazards and risks associated with the changes.
The speed of change of climate and its amount and characteristics are the subject of Part Two, but for estimating the rank of climate change these things must be multiplied by the chance that the changes will happen. Other
things being equal, the uncertainty of scenarios reduces the rank of climate change as an issue.
The findings in Part Four about impacts of climate change generally agree with those of other U.S. and international investigations (Smith and Tirpak, 1989; United Nations Environment Programme and The Beijer Institute, 1989; Intergovernmental Panel on Climate Change, 1990). We, however, direct most of our attention to adaptations rather than to impacts.
Enormous uncertainties attend any analysis of climate change and adaptation to it. The present report is necessarily only a statement of present knowledge and is thus a beginning. One of its functions is encouraging further assessments, especially of the indirect costs of adaptation.
An activity that is affected by a change in the weather tomorrow could be insensitive to climate change if it were adaptable and its renewal were faster than the rate of climate change prolonged through decades. If we ignore adaptations, we imagine the climate near the middle of the next century imposed on the people of today, the way they live, and their current natural environment. So, adaptation can change the sensitivity to climate change as time passes and thereby change its rank as a policy issue. The reader will read below that human activities can change fairly rapidly and natural ecosystems more slowly, whereas evolutionary adaptation by genetic changes in populations of organisms is generally even slower.
Humanity and Nature Have the Potential to Adapt
Human adaptability is shown by people working in both Riyadh and Barrow and seeking out both Minneapolis and Galveston. Recent American migration has on average been toward warmth.
There are limits on the speed of human responses. These limits make not only the direction but also the rates of climate change crucial. People need time to adapt in situ to a new climate or to move to a region of preferred climate. If they move, they must find places where the other components of the environment, like soil and water, also fit them. Although time is taken to adapt managed things like farming, the historical evidence suggests that American farmers can keep up with gradual climate change of the magnitude the panel assumes.
The capacity of humans to adapt is evident in the rapid technological, economic, and political changes of the past 90 years. The average renewal period for machinery and equipment and the average age of buildings are one to three decades. So, through continuing normal investment, humanity's business activities have the potential to adapt during the next half century to the types of changes upon which our analysis is predicated.
Another factor that may limit adaptation is water. Some activities, like
irrigation or cooling, use it in large quantities. Agriculture is highly dependent upon it. Transporting large quantities great distances is possible but expensive and illustrates the environmental costs that adaptations may exact. Therefore, changes in the amount and distribution of precipitation could have serious consequences for human activities in some regions.
Animals and plants live in the Himalayas and in Death Valley, in Manaus and Antarctica. Particular species, however, may not be able to adjust to climate changes rapidly enough to survive in a given location. Again, rate, as well as direction, of climate change is crucial. Under stress, natural systems of plants and animals tend to break up and reformulate in new systems with different species or mixes of species. Thus, the specific mix of plants and animals, that is, an ecosystem suited to a specific arrangement of earth and climate, may disappear from a place if climate changes. Assisting the movement of such ecosystems to suitable new locations may be hard or impossible. Although plants and animals will always be found regardless of climate changes, they may not be the same communities that were there before the changes took place, and some species may become extinct.
A final limit, and a common one, is money. Adaptations like furnaces and air conditioners, sea walls and canals, take money. Resources for such investment require continuing ability to generate wealth.
Some Indices Matter More
Global averages are inappropriate as foundations for thinking about impact or adaptation. Because most adaptations are local, their cost cannot be estimated until such factors as water supply and temperature changes can be predicted in specific regions. An analysis of likely effects of climate change suggests several strategic indices about which detailed and extended information is important. The indices are rates and directions of change in:
• First, the flow of water in streams and its supply in soils of a region, including its variation from season to season and year to year. These are important because stream flow integrates many aspects of water availability, and soil moisture is the water actually available to plant roots.
• Second, changes in sea level and height of waves on a shore, because many people are on seashores.
• Third, any major shifts in ocean currents, because changes in those currents could have major climatic implications.
• Fourth, the timing of seasonal events like blooms and migrations, because such changes may signal adjustments in those systems of importance for their functioning.
• Fifth, untoward extremes of heat and cold, because extreme events may evoke the need for adaptation and set the limits on adaptation by people and other organisms.
Because weather is variable, long-term records will be needed to detect changes in climate. Nonetheless, monitoring the local climate, including the water in streams and seasonal events, is crucial over spans of decades and will eventually provide a basis for determining which adaptations are most needed.
Some Activities Have Low Sensitivity
Just as an effective strategy requires ranking climate change with all the other changes ahead, it also demands ranking sensitivity and adaptability of human activity and nature into classes of sensitivity and adaptability to climate change alone. Attention can then be concentrated on sensitive areas. Table 30.1 summarizes the ranking the panel made.*
Fortunately, human activities that bulk very large in the national incomes of modern developed countries have low sensitivity to gradual climate change. In addition to having low sensitivity, such activities as industry and the provision of energy are adaptable because machinery and buildings are renewed faster than the projected climate change. So industry should have little trouble adapting.
The climatic changes upon which our analysis is based are within the range that people now experience where they live and to which those who
*Panel member Jane Lubchenco believes that ''Table 30.1 and the related scheme used in this analysis, though useful as a preliminary organizing framework, are misleading because they imply that the activities and systems are independent and distinct from one another." She points out that "a comprehensive assessment of the feasibility and costs of adaptations must include the interactions and interdependencies among the various activities and systems. For example, the impacts of climate change on economic activities are considered separately, sector by sector (farming, industry, etc.). While this is perhaps understandable given the difficulty of analyzing the interactions, conclusions made without considering them may be faulty. Of particular concern are the indirect costs, such as the environmental costs of various adaptations, which for lack of time and information, the panel did not evaluate.
"The incorporation of environmental costs of adaptations is especially relevant in light of the suspected causes of greenhouse warming. Our current understanding of greenhouse warming supports the conclusion that the predicted climate changes are a result of unforeseen environmental consequences of 'adaptations' to the environment. Examples include the burning of fossil fuels to provide electricity or motive power, or the use of CFCs to cool buildings or automobiles. These are adaptations by one 'activity' (sensu Table 30.1) that have serious consequences to other activities or systems. A comprehensive evaluation of adaptation strategies will include a broader view than the system-by-system or activity-by-activity approach adopted in this report. Moreover, divorcing humans from their ecosystems ignores the intimate, if often complex and subtle, dependencies of humans on the natural environment.
"In addition, the observation that there are examples of particular system types currently located in substantially different climatic conditions says little about the ability of a system in a particular location to adjust to changing climate. This is especially relevant for natural ecosystems which, as the report points out, are unlikely to be able to adjust as rapidly as conditions change."
TABLE 30.1 Sensitivity and Adaptability of Human Activities and of Nature to Climate Change Alone (climate is assumed to change gradually by an amount of 1° to 5°C when the planet reaches equilibrium with an equivalent of doubled CO2)
move usually learn to adapt. The pace of improvements in health from better technology and public measures can and likely will exceed any deterioration from climate change. Epidemics from causes already known, failure to control population growth, and chemical pollution are more serious threats to human health than climate change.
Some Activities are Sensitive but Can be Adapted at a Cost
As the most valuable outdoor activity, farming would add most to the impact, up or down, of climate change on national income. Experience
shows that farming is continually adapted to cope with, even exploit, climate and its stresses and fickleness. Adaptations to climate change will be required in both rich and poor countries and to protect both crops and their foundation of soil and water. Since adaptation will be at a cost, poor nations may adapt painfully. Although less thoroughly managed than farming and while growing a crop with a long life, forestry can also be adapted.
Water supply is vital to all human activities and is sensitive to climate. Fortunately, although its adaptation can be costly in money or inconvenience, experience shows it is possible in many circumstances. Developing better management systems for dealing with present droughts and floods is a vital component of such adaptation.
Should climate warm, most cities will adapt rather than abandon their sites. Although the adaptation may be costly, the costs will be cheaper than moving the city. By far the biggest costs will be in coastal cities if the sea rises, whereas the direct costs from warming will be small. Because the infrastructure of cities is fairly long lived, some adaptations in advance will become profitable if the chance of climate change is high, the wait until the adaptation is needed is short, and the discount rate of money is low.
Since tourism and recreation exploit climatic differences from snow fields to desert oases and although local dislocations will occur, these activities seem adaptable to climate change at little net cost.
Where adaptation is the replacement of one region or activity by another, a small net cost for the nation may be comprised of counteracting winnings and losses. Some regions may win a new activity while it becomes untenable and is lost to another. Also, the same person may have winnings and losses, as by losing skiing and winning swimming or losing barley and gaining corn. Small net differences may result from substantial pluses and minuses.
Some Activities are Sensitive and
or Adjustment is Questionable
In the unmanaged systems of plants, animals, and microbes that are much of our landscape and oceans, however, the pace of change of some key processes may be as slow as or slower than climate change, making their future problematic. They have a slower response and hence greater sensitivity to climate change than the managed systems of crops on a farm or timber in a plantation.
Their slow response comes from the long lives of some of their components, like trees in the natural landscape that last longer than the ones planted for timber. It comes from the slow and chancy arrival of seed and birds traveling on the wind, in currents, or along corridors rather than in the trucks of farmers. It comes from plant succession on an acre of wild
land or in an estuary taking decades or centuries, and it comes from evolution taking aeons. Climate change will not likely make land barren except at the arid extremes of existing climates. What is likely are changes in the composition of ecological communities in favor of those species able to move rapidly and far and the disappearance of some species that move slowly. The impacts of such changes on the functioning of ecological systems, and the consequent impacts on human society, cannot be predicted with confidence.
The Impacts of Some Conceivable Climate Changes are Large but cannot be Assessed
Although we know of no way to compute the probability of cataclysmic changes on the planet, like the reversal of the ocean current that warms Europe, large changes of climate have happened. New diseases and prolonged wars have caused calamitous centuries. Desperate masses have fled drought in places with marginal farming and growing populations. These disasters were not necessarily related to greenhouse gases, but they could be exacerbated by rapid future climate changes. Clearly, trends of economic and social development have lessened the vulnerability of many societies to climate. At the same time, trends such as increasing populations in river flood plains and low coastal areas have increased the vulnerability of some regions and nations. So, even if the United States could, by and large, adapt to climate change, the misfortunes of others unable to do so could substantially affect the United States and other industrial countries.
Over the next 50 years some nations will probably reduce their vulnerability to climate change, but others may become more vulnerable. Although migration is possible and domestic tranquility can sometimes be maintained, major climate changes could overtax societal capabilities, especially of poor countries. The probability and nature of such unexpected changes are unknown. Therefore, we cannot predict their impacts or devise adaptations to them.
Intergovernmental Panel on Climate Change. 1990. Climate Change: The IPCC Impacts Assessment, W. J. McG. Tegart, G. W. Sheldon, and D. C. Griffiths, eds. Canberra: Australian Government Publishing Service. Available, in the United States, from International Specialized Book Service, Portland, Oregon.
Smith, J. B., and D. A. Tirpak, eds. 1989. The Potential Effects of Global Climate Change on the United States. Washington, D.C.: U.S. Environmental Protection Agency.
United Nations Environment Programme and The Beijer Institute. 1989. The Full Range of Responses to Anticipated Climatic Change. Nairobi: United Nations Environmental Programme.