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32
Issues, Assumptions, and Values
Three questions frame the study of climate change: Is it
happening? Can we stop it? How can we cope with it? Asking the
third question may seem pessimistic. Nevertheless, if during the
past two centuries mankind has committed the planet to a new
climate, it must be answered. On the other hand, if the planet is
not yet committed, balancing the cost of stopping climate change
against its result still calls for an answer. And, if humanity is
not changing the climate, we need to know how to cope with natural
variations in weather and climate. So, against a background of
present climatic differences from place to place and changing
weather from day to day, the Adaptation Panel here tries to answer
for Congress the final "How can humanity cope with climate
change?"
Definitions
Simply put, climate is the average state of the weather. At a
deeper level, the climate of a locality is the synthesis of the
day-to-day values of the meteorological elements that affect the
locality. Synthesis implies more than simple averaging. Various
methods represent climate, for example, both average and extreme
values, frequencies of values within ranges, and frequencies of
weather types. The main climatic elements are precipitation,
temperature, humidity, sunshine, wind, and such phenomena as fog
and frost. Climatic data are usually stated in terms of an
individual month or season (McIntosh, 1972).
The critical matter is that climate is the accustomed seasons,
daily cycles, variations, and ties among the factors of weather at
a given place. The question is whether the nature and civilization
that have evolved in the climate of a place will be greatly
affected by or can easily adapt to the
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future climate. Nature, here, means the natural or unmanaged
living things outdoors. Humanity, of course, is part of nature, but
we use the word nature to mean the unmanaged environment. In the
past the study of the outcome of climate change for nature and
humanity dealt largely with the impacts, or blows, themselves.
Studies have dealt, for example, with the changes a new climate
would cause in the plants of an ecosystem, the yield of a crop, or
the safety of a seawall, assuming little or no adaptation. Here the
panel integrates projections of impacts into its discussion of how
to cope (see Chapter 34).
The most severe challenge in weighing impacts, however, is to
compound the outcome of a changing climate with other changes that
will occur during the coming decades. These changes range from
technological innovations to social changes and from increased
numbers of humans to ecological impacts. We can grasp the possible
magnitude of some of the kinds of changes that might happen at the
same time as a climate change by looking back eight decades. In
1910 the Ottoman, Austro-Hungarian, British, and Russian empires
ruled much of the world. In America there were no income taxes,
women could not vote, each person commanded 1.5 horsepower, and the
major polluters were the 21 million horses (Nordhaus, 1990).
Although the crystal ball for seeing future life and technology
is cloudy, the magnitude of the changes of the past 80 years
teaches us that we must go beyond computation of the effect of
warming of 1° to 5°C on, say, today's corn or coast. We
must try to foresee the adjustments in nature and human behavior
that will occur in response to changing environmental conditions
amidst an army of technological, social, and economic changes. If
we ignore these adjustments, which are here termed adaptations, we
will write a "dumb people scenario." Imposing the climate near the
middle of the next century on the activities of 1990 implicitly
assumes that people will dumbly ignore any new environment and
circumstances for 80 years and behave as they do today.
Three classes of adaptation by humans can be distinguished
(Coppock, 1990). The first might be called adjustments. These are
prompt, individual, uncoordinated, and largely spontaneous, such as
the changes a farmer makes in crop varieties after a couple of cold
years. A second class, which might be called premeditated
adaptation, begins with anticipation and information and requires
planning, coordinated action, and time. This class is typified by
the building of a dam for irrigation. A third class might be called
interventions. These actions, typically by governments, manipulate
the circumstances of choices and are exemplified by the zoning of
wetlands. Here, the word adaptation encompasses all these.
An illustration of a dumb scenario is a vision of the corn
varieties and husbandry of 1990 in a changed climate in 2030 and
then calculation of the impact of climate change as a change from
the 1990 yields. A smarter
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scenario is a vision of a crop changing for four decades in the
future by methods and along a trend somewhat as in the past.
Yields, too, would follow a trend, which would be a baseline or
reference. With no adaptation to climate, future yields would
deviate from that baseline, up if the climate change were favorable
and down if it were harmful. Adaptation would change the yields,
and, if the climate change were harmful, the adapted yields would
lie between the rising baseline of no climate change and the trend
of yields not adapted to the changing climate. In the smarter
scenario, the impact of climate change would be the net sum in 2030
of the costs of adaptation and the difference between the baseline
of yield in an unchanged climate and the yield of the adapted crop
in the changed climate.
Ask a farmer who is 70 or 80 years old what is different now
compared to when he was a child. He would likely find changing from
horses to tractors, from dirt to paved roads and from open
pollinated corn to hybrid corn plus the arrival of soybeans and
pesticides swamped the assumed climatic warming of a half to whole
degree during the 20th century.
Similar illustrations could be drawn from other activities.
Figure 4.1 of Part One shows the general case.
Estimating cannot be precise, but the panel realizes or foresees
the following:
• The impacts of climate change must be sorted out from
other effects caused by simultaneous changes in other factors.
• The baseline or reference of what would happen without
climate change will trend up or down.
• The impact of climate change is the net of the cost of
adaptation plus or minus the residual change from the baseline that
occurs despite adaptation.
• The net impact of climate change can be negative, or, if
the residual change is a help greater than the cost of adaptation,
the net can be positive.
Assumptions
Studies of the impacts of climate change commonly begin with a
climate scenario. Will it be 1°C or 5°C warmer? Will 10
percent more or less rain fall? And so forth. But these
specifications are shaky at best and only compound the uncertainty
already inherent in the complex response to climate.
To some extent, however, the studies of outcome can be
independent of the climate scenarios. An activity like farming or
forestry will be different in the future than it is today. If
climate changes, part of that difference will be the impact of
climate change. If the sensitivity to climate of the activity is
constant, the impact is simply the climate change times the
sensitivity. In that case a student of outcomes can estimate the
sensitivity and then leave it
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Representative terms from entire chapter:
intergovernmental panel
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to others to calculate the impact of climate change by
multiplying the constant sensitivity by any scenario proposed.
More formally, let the rate of change of activity A be
dA/dt. Then let the rate of change dA/dt of A
equal the sum of products of sensitivities to factors times the
rates of change of the factors. Since our subject is climate, the
first product is the sensitivity
dA/d(climate) of A
to climate times the rate of change d(climate)/dt.
Bringing together all the other factors that affect A, we
let the second and remaining product be the sensitivity dA/ d(other
factors) of A to other things times the rate of change
d(other factors)/dt. The relative importance of climate
change to A depends on its sensitivity to both climate and
other factors and on the rates of change of both climate and other
factors. Finally, if the sensitivity to climate is unchanged by,
say, adaptation or climate, the impact of climate change is simply
the constant sensitivity dA/d(climate) times the change in climate, which
is the integral of d(climate)/dt. In this last case,
studies of sensitivity can be separated from scenarios.
Still, there is a limit to the separation of studies of
sensitivity from assumptions of climate change. The sensitivity,
dA/d(climate), depends on the value of climate.
For example, the sensitivity of a tomato per degree is different
from 5° to 15°C than at the threshold of 0°C, where it
freezes. The sensitivity of a marsh to a sea rising 1 m is not
likely to be just 10 times its sensitivity to a rise of 10 cm. The
sensitivity of a 1-m wall to 50-and 150-cm rises in sea level is
utterly different.
So the panel did not have to assume a precise climate scenario,
but it did have to assume the sort and order of climate change. The
scenarios that are supportable, the forecasts of climate change,
and the warnings about the uncertainties of the forecasts were
provided by the Effects Panel. Briefly, they are, in the absence of
human efforts to mitigate emissions:
• Greenhouse gases will reach the equivalent of 600 ppm
CO2 near the middle of the 21st
century.
• Mathematical models project that this increase of
greenhouse gases will warm the planet 1° to 5°C, on
average, over the temperature of about 1990. This warming would be
achieved if the planet comes to equilibrium with the 600 ppm.
• The warming actually realized during the past century
appears to be 0.3° to 0.6°C. Simple logic suggests that lag
will make the realized warming by the middle of the 21st century
less than the warming at equilibrium with the 600 ppm.
• The projections are plagued by uncertainties about the
accumulation of the gases and their absorption and the roles of
oceans, clouds, and other environmental elements.
• Projections about the climate of a locality are doubly
uncertain. Precipitation may be tens of percent more or less than
now.
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• A rise in sea level may accompany global warming,
possibly in the range of 0 to 60 cm for the timing and temperature
range listed above. These assumptions about the physical
environment are consistent with those made by others (National
Research Council, 1983; Smith and Tirpak, 1989; Schneider et al.,
1990).
The assumed increase of greenhouse gases to 600 ppm near the
middle of the 21st century implicitly assumes that population and
economic activity will increase. The growth of material well-being
is relevant, as it partly determines what adaptations are
affordable. In its studies of policy responses, the Environmental
Protection Agency (EPA) assumed a world growth rate of less than 1
percent per year for their slowly changing (low-emission) world
scenario and over 2 percent per year for their rapidly changing
(high-emission) world scenario (Lashof and Tirpak, 1991). The
Intergovernmental Panel on Climate Change (IPCC) assumed that
annual economic growth would be 2 to 3 percent in Organization for
Economic Cooperation and Development (OECD) countries and 3 to 5
percent in Eastern Europe and developing countries during the
coming decade and slower thereafter (Intergovernmental Panel on
Climate Change, 1990). The Adaptation Panel assumed a positive
growth of material well-being without specifying it precisely. To
assess costs of impacts and adaptations, a further financial
assumption on discount rates is required. The Adaptation Panel used
discount rates of 3, 6, and 10 percent in its analysis.1
To gauge impacts and foresee adaptations, however, the panel
also needed to go beyond a generality like "1° to 5°C
warmer on average" to consider how the climate affecting a
community might be transformed year by year. Alternatives are
depicted in Figure 32.1. The top panel shows a frequency
distribution and no trend for a climate steady in its average and
variability. The second panel shows one sort of change: The
frequency distribution is unchanged in its shape and spread but
shifted left because the average falls. The fall could be either
steady or sudden. The third panel shows another sort of change: The
average is unchanged, but the variability is increasing. It could,
of course, have been drawn with decreasing variability. The final
panel shows both the average falling and the variability
increasing.
The effects associated with a global cooling of roughly 5°C
during the last ice age 18,000 years ago are known, and a
repetition would crush the upper midwestern United States under
ice. No similarly dire outcome has been found associated with a
5°C warming. None of the projected effects of the warming would
make large areas uninhabitable. So while we complain about the
uncertainty of warming by greenhouse gases, we should not forget
that it would make any effects from cooling, which was a subject of
some scientific, public, and congressional concern in the early
1970s, less likely.
Because computing the average temperature is hard enough,
scenarios
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FIGURE 32.1 Several ways climate could change,
as illustrated by courses of temperature.
SOURCE: Adapted
from Riebsame (1988).
usually give only the average that would be reached at
equilibrium for an equivalent CO2
doubling. Nevertheless, some recent efforts to compute the
variability in the new climate foresee a shift in the average
temperature without a change in variability (Mearns et al., 1989,
1990; Rind et al., 1989;Smith and Tirpak, 1989). A projection of no
great change in variability is not inconsistent with the statement
by IPCC Working Group I that neither more nor fewer storms could be
predicted for the future climate (Intergovernmental Panel on
Climate Change, 1990).
Turning from temperature to precipitation, one encounters fully
the need for regional and seasonal predictions of the frequencies
of drought and flood. Yet predicting even the change in averages is
beyond present skill.
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A comparison among the frequency distributions of precipitation
today, however, hints at how their interannual variability would
usually change if the average changed. If the average falls, the
absolute interannual variability, measured by the variance, would
fall. The relative variability, measured by the ratio of the
standard deviation to the average, however, would increase.
Skewness would also increase.2 Since
precipitation cannot be less than zero, future changes in its
frequency distributions will generally resemble these differences
among its present ones.
A final question concerns the path from the present to future
climate. The panel concentrated on a gradual change like the upper
trend in the second panel of Figure 32.1. As drawn, the trend might
represent a change to less precipitation. If the trend were drawn
up, it might represent a change to warmer temperatures. Annual
variations around the trend will, of course, continue, and
sometimes several years that are above or below the trend will
mislead people. A gradual change is not a surprising effect of the
gradual increase in greenhouse gases that forces the change, and a
gradual change is generally consistent with the computations of
models. The panel recognizes that the passage of some threshold or
shifting ocean current might cause an abrupt, harmful change. We
were unable to evaluate the likelihood of these events, and, while
recognizing their potential for significant impacts, we have not
analyzed their impacts or adaptations to them. The ability to adapt
to every extreme outcome of climate change is, of course, in doubt.
This report concentrates on the range of the changes that might
occur within the next half century or so and that are stated in the
assumptions above. Within that range, moderate changes seem more
likely than radical ones. The IPCC stated that business as usual
would likely raise the global mean temperature above the present
one by about 1°C by 2025 and 3°C before the end of the next
century (Intergovernmental Panel on Climate Change, 1990).
Furthermore, examining the consequences of, say, a warming of
1°C makes sense even if the eventual warming is greater because
the planet would first warm 1°C before warming more. The
effects of abrupt and radical changes might well be examined in the
future if the physical logic for them becomes convincing. For now,
however, the panel concentrated on moderate changes.
In the end panel considered the sensitivities and adaptations to
a gradual change in averages without a great change in variability
to climates warmer by a few degrees, where precipitation is tens of
percent more or less than at present and the sea is 20 to 30 cm
higher by the middle of the next century.
Economic and Ethical Values
In much of the world, certainly in the United States, suppliers
signal their willingness by prices and then buyers vote their
wishes in markets.
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Fundamentally, the economic view is centered on humanity. The
activities that are worthwhile in this view are valued by people
and expressed in market and political decisions. The economic view
is not that nature is without value but that nature's value derives
from human values about nature. If people do not care about the
landscape, whales, and snails, as shown by their dollars and votes,
these things will have no economic worth. On the other hand, in a
society that loves the environment, high values and high prices
would be placed on parks, wetlands, and open spaces, and these
values would carry over to private transactions and legislative
mandates.
In a preliminary economic analysis of the impact of climate
change, the 1981 national income of $2.4 trillion was divided into
16 sectors. Their sensitivity ranged from the potentially severe
impact on farms and forests to the negligible impact on mining and
manufacturing. The calculated direct impact of climate change on
the national income would be about 1 percent (Nordhaus, 1991). The
estimate is only 1 percent because, among other things, the impact
on sensitive agriculture may be positive or negative and the impact
on the valuable manufacturing and service sectors is negligible.
Although the absolute number of dollars may be large, the relative
amount of 1 percent is a discouragement for large investments in
climate change.
Although the national income accounts capture only the value of
marketed goods and services, it is possible to incorporate goods
like environmental quality that are not marketed or priced
accurately, if at all (Coomber and Biswas, 1973). These
environmental intangibles are generally outdoors and so exposed to
climate. The incorporation of these nonmarket goods and services
might increase the sensitivity of the economy to climate
change.
Beyond intangibles that can be assigned a price are ethical
values. An appraiser might devise a formula, for example, to give a
price for a shade tree, adding it to the value of a home. Beyond
that appraisal, however, lies the ethical question of whether it
should be cut down, especially if birds are nesting in it.
If our present evolutionary impetus is an upward
one, it is ecologically probable that ethics will eventually be
extended to land. The present conservation movement may constitute
the beginnings of such an extension. If and when it takes place, it
may radically modify what now appear as insuperable economic
obstacles to better land use (Leopold, 1933).
All these ways (i.e., economics of marketed goods and services,
economics of nonmarket goods and services, and ethical arguments)
of measuring human well-being and the quality of our stewardship of
the planet need to be taken into account in assessing the
seriousness of the impacts of climate change and the potential and
appropriateness of adaptations. Taking them into account, of
course, requires judgment as well as evidence and computation, and
the panel has tried to take these into account fairly in judging
findings and eventually recommendations.
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Notes
1. As the exercise in Chapter 33, the section "Making Decisions
in an Uncertain World," demonstrates, the assumption of a discount
rate is important for adaptation. Rates are crucial for weighing
mitigations, which are anticipatory, and rates are discussed at
length in Part Three: Mitigation. The rates of 3, 6, and 10 percent
are also found in Part One: Synthesis. For growth of incomes see
Table 34.1.
2. Among 660 cases of 12 monthly distributions of precipitation
at 55 stations, the variance increased as the 1.3 power of the
mean. This specifies that both the coefficient of variation and the
skewness of the frequency distribution vary as the -0.35 power of
the mean (Waggoner, 1989).
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