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30
Findings
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
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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
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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.
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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."
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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)
Subject
Class
Farming
Sensitive but can be adapted at a cost
Managed forests and grasslands
Sensitive but can be adapted at a cost
The natural landscape
Sensitive and adaptation is questionable
Marine ecosystems
Sensitive and adaptation is questionable
Water resources
Sensitive but can be adapted at a cost
Industry and energy
Low sensitivity
Tourism and recreation
Sensitive but can be adapted at a cost
Settlements and coastal structures
Sensitive but can be adapted at a cost
Health
Low sensitivity
Human migration
Sensitive but can be adapted at a cost
Domestic tranquility
Sensitive but can be adapted at a cost
NOTE: In the order of the outline of Chapter 34,
the subjects are classified as: Low Sensitivity, Sensitive But Can
Be Adapted at a Cost, and Sensitive and Adaptation is Questionable.
Since sensitivity is the change in an activity per change in
climate, the impact of sensitivity times climate change will be
positive or negative according to the climate change. Adaptation
modifies sensitivities as, for example, a lessening during the 20th
century of the annual cycle of human mortality demonstrates. Given
great wealth, a society might move some things from the third class
of questionable adaptation to the middle class of sensitive but
adaptable at a cost. Or, without the wealth for adaptation, a
society would be unable to adapt to things in the second class.
Natural and social surprises not analyzed would, of course, alter
the classifications. Surprises, for example, could either remove
migration and domestic tranquility from the list or overwhelm even
costly attempts to adapt. For the climate changes assumed here and
for the United States and similar nations, however, the
classification is justified.
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
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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
Their Adaptation
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
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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.
References
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.
Representative terms from entire chapter:
low sensitivity
