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Page 7
1
Climate Variability, Climate Forecasting, and Society
The 1997-1998 El Niño provides a dramatic example of the
effects relatively short-term climatic variations have on society
and the potential value of forecasting them. The key indicators of
a strong El Niño, including a sharp rise in sea surface
temperature in the tropical Pacific Ocean, were detected by March
1997. Sea surface temperatures in the Eastern Pacific reached
record values of 5 degrees Celsius above normal by June, and
researchers were comparing the strength of the event to the
1982-1983 El Niño and recalling the worldwide impacts of
that event. What made the 1997-1998 El Niño different was
that scientists were monitoring the event as it developed and
making predictions of its evolution 3 to 6 months ahead. Although
the forecasts disagreed somewhat on the intensity, timing, and
geographic extent of the emerging event, there was sufficient
agreement for several national meteorological services, including
the National Oceanic and Atmospheric Administration (NOAA), to
issue advance advisories. The media interest in these predictions
was unprecedented, and a number of groups took steps to prepare for
the impacts.
In the U.S. state of California, preparations for the predicted
higher-than-average winter precipitation and unusually severe
storms included government planning for emergency response, the
reinforcing of hill slopes and coastal defenses, and insurance
purchases and roof maintenance by homeowners. More than $100
million was spent on levee repairs and, in the last quarter of
1997, California flood insurance policies increased by 40 percent.
Between January and May 1998, California re-
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Page 7
1
Climate Variability, Climate Forecasting, and Society
The 1997-1998 El Niño provides a dramatic example of the
effects relatively short-term climatic variations have on society
and the potential value of forecasting them. The key indicators of
a strong El Niño, including a sharp rise in sea surface
temperature in the tropical Pacific Ocean, were detected by March
1997. Sea surface temperatures in the Eastern Pacific reached
record values of 5 degrees Celsius above normal by June, and
researchers were comparing the strength of the event to the
1982-1983 El Niño and recalling the worldwide impacts of
that event. What made the 1997-1998 El Niño different was
that scientists were monitoring the event as it developed and
making predictions of its evolution 3 to 6 months ahead. Although
the forecasts disagreed somewhat on the intensity, timing, and
geographic extent of the emerging event, there was sufficient
agreement for several national meteorological services, including
the National Oceanic and Atmospheric Administration (NOAA), to
issue advance advisories. The media interest in these predictions
was unprecedented, and a number of groups took steps to prepare for
the impacts.
In the U.S. state of California, preparations for the predicted
higher-than-average winter precipitation and unusually severe
storms included government planning for emergency response, the
reinforcing of hill slopes and coastal defenses, and insurance
purchases and roof maintenance by homeowners. More than $100
million was spent on levee repairs and, in the last quarter of
1997, California flood insurance policies increased by 40 percent.
Between January and May 1998, California re-
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Page 8
ceived 228 percent of normal precipitation (NOAA press release,
June 8 1998, El Niño and Climate Change record temperature
and precipitation), and by June 1998 the state was estimating $500
million in property damage (USA Today, June 12, 1998). In
other regions of the United States, El Niño was blamed by
some for an unusually high number of tornadoes, resulting in more
than 120 deaths.
On the positive side, El Niño was credited for unusually
warm winter weather in the Midwest and the Northeast that brought
lower heating costs for consumers, downward pressure on oil prices,
a longer construction season, decreased snow removal costs, and
other benefits. On the East Coast, no hurricanes hit land in the
1997 hurricane season, which reduced disaster losses but increased
fire risk in Florida. In the Southwest, where El Niño
brought more winter rains, the increase in vegetation and
wildflowers boosted tourism but increased allergies and concerns
about diseases such as hantavirus.
In Latin America, as reported in The Economist (May 9,
1998), the costs attributed to El Niño were large. Drought
caused water shortages, crop failures, and wildfires in Mexico,
Central America, the Caribbean, Colombia, Venezuela, and northeast
Brazil. Floods drenched Ecuador, Peru, Chile, Argentina, Paraguay,
and Uruguay, and fall hurricanes struck Mexico's Pacific coast. El
Salvador's coffee production dropped by 30 percent, and the
Colombian government reported a 7 percent drop in agricultural
output because of drought. In northeast Brazil damages were
estimated at $4 billion. Nine million Brazilians suffered from food
shortages, and more than 48,000 square kilometers of forest burned
in the state of Roraima. In drought-stricken Central America and
Colombia, urban areas relying on hydropower had long power cuts. In
Mexico, 400 people died when Hurricane Pauline hit Mexico's Pacific
coast in October 1997 (Gobierno de Oaxaca, 1997); the hurricane's
intensity was widely attributed to El Niño. Forest fires
caused by drought due to El Niño burned about 400,000
hectares in Mexico in spring 1998 (Comision Nacional Forestal,
1998).
Although the Peruvian government, heeding the forecasts, had
prepared for rains by rebuilding dikes and reinforcing bridges at a
cost of $300 million, the floods destroyed more than 300 miles of
roads and 30 bridges and displaced 300,000 people. In Ecuador,
infrastructure damage from floods exceeded $800 million. In
southern South America, the Paraná and other rivers
overflowed, displacing thousands of people, killing cattle and
destroying crops. The losses in Argentina were estimated at $3
billion. Fish catches declined, particularly in the Chilean and
Peruvian anchovy and mackerel fisheries.
In Asia, El Niño was associated with drought and vast
forest fires in Indonesia and with heat waves in India. In
Australia, it was associated
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with unusually dry conditions. However, in southern Africa,
where governments prepared by building food reserves, the
devastating droughts that had occurred during the 1982-1983 El
Niño were not repeated in 1997-1998, and the rainy season
(until June 1998) was relatively normal.
From a health perspective, the extreme weather events were
associated with many disease outbreaks. In Latin America, flooding
was associated with significant upsurges in malaria and cholera in
Ecuador, Peru, and southern Brazil. Heavy rains in the Horn of
Africa precipitated outbreaks of cholera, malaria, and Rift Valley
fever. In Asia, drought was associated with poor water quality and
cholera. The massive forest fires in Indonesia, as well as in
Brazil, Mexico, Central America, and Florida, inflicted widespread
respiratory illness. Poor air quality also affected trade and
tourism, and fires in tropical forests have adversely affected
wildlife and ecosystem functioning, as well as releasing additional
carbon into the atmosphere (Epstein, 1998; Stevens, 1998).
In addition, high sea surface temperatures have taken an
enormous toll on sea life, especially marine mammals. During
1997-1998, significant marine mammal mortalities were linked to El
Niño on the Pacific coasts of the United States, Peru,
Venezuela, and the Galapagos Islands and in the southeast Pacific,
New Zealand in particular (Epstein, 1998; Stevens, 1998). These
effects may have been caused by the migration of food sources,
enhanced blooms of toxic phytoplankton, and/ or changes in the
immune systems of marine mammals.
In sum, the 1997-1998 El Niño had major negative impacts
on many people and regions and also brought significant benefits to
other people and regions. The availability of accurate forecasts of
extreme weather led some people and organizations to act in ways
that spared them even worse damage. However, many others in these
areas did not hear or respond appropriately to the forecasts, and,
in other areas, forecasts were wrong and some prepared for forecast
disasters that did not arise.
The experience of 1997-1998 strongly suggests that there is
great potential social value in the developing ability to forecast
climate—averages of temperature, precipitation, and the
like—months to a year or more in advance. Improved forecast
skill, that is, accuracy beyond annual and seasonal averages,1 may open up a vast array of
possibilities for the use of climate information to reduce the risk
of damage from unfavorable cli-
1 The term
''forecast skill'' has precise meanings in meteorology. Commonly,
skill is measured by the correlation between the forecast and
actual values of an index of some weather or climatic event or by
the average of the root-mean-square error over the length of a
forecast (National Research Council, 1996a). The concept of
forecast skill is described further in Chapter 2.
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Page 10
matic events and to seize the benefits of favorable ones. A
premise of this study is that improved climate prediction can
reduce the negative effects and enhance the positive effects of
seasonal-to-interannual climate variability.
However, it seems clear that only a portion of this potential
has so far been realized. We do not fully know how people responded
to the predictions of the most recent El Niño, how much
benefit the forecasts brought to those who did respond, or how much
additional benefit there might have been if responses had been more
appropriate and widespread. We also know little about how seasonal
climate forecasts should be organized and forecast information
disseminated in order to have the best possible effects. This book
examines what is known and what needs to be known to enable climate
forecasting to achieve its potential value for society.
To address this issue, we raise and discuss a broad array of
questions. How well adjusted are human systems to the various forms
of seasonal and interannual climatic variation, from the
commonplace fluctuations that people ordinarily expect and prepare
for to infrequent, extreme events that cause major disruption?
Which economic sectors, segments of populations, or regions seem
most sensitive to seasonal-to-interannual climatic variability?
What is the net impact of a major climatic event such as the recent
El Niño, and how is it distributed among those who suffer or
benefit? How can one separate the impact of such a climatic event
from other simultaneous influences on economies, ecosystems, and
societies? Are those who are sensitive to seasonal-to-interannual
climate variability able to use improved climate forecasts to
improve efficiency or reduce risk? If they are able, under what
conditions do they use climate forecasts to improve their
well-being? How did people and organizations respond to the most
recent forecasts and interpret the uncertainties in them? Why did
some countries, organizations, and individuals respond when others
did not? What role did mass media coverage play in public
perceptions and institutional responses to the event? How will the
perceived success of the most recent predictions affect responses
to future forecasts? What will be the effect of the forecasts'
failure in some regions? How can future forecasts be made more
useful than those of the past? This book considers how to develop a
research program aimed at answering such questions. Such a research
program would have two main goals:
•
to understand the consequences of seasonal-to-interannual
climate forecasts for human groups and for societies as a whole,
and
•
to make these forecasts more useful.
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Climate Variation And Society
The climate system is a fundamental natural resource of the
earth. It is driven by the sun and contains the gases necessary for
photosynthesis, and is thereby the foundation of all food chains
necessary for human life. It keeps the temperatures on the earth's
surface within the narrow range tolerated by life. It drives the
biogeochemical cycles that distribute nutrients and water about the
biosphere. It delivers the water for shipping, irrigation,
municipal consumption, and hydroelectric generation. It generates
wind to turn windmills and makes snow for skiers. It also provides
warm, sunny days that please the senses. In short, climate is
thoroughly involved in virtually every aspect of the environment
and human activity.
Human beings and societies have always had to cope with
variations in weather—shifts of wind, temperature and
precipitation that can be extreme and that are experienced on the
time scales of minutes, hours, and days. Humanity has also always
coped with variations in climate—averages of weather on longer
time scales. Seasonal variations affect the need for clothering and
the availability of food and water, and people have responded by
varying their diets and clothing and developing systems of building
construction and food and water storage. And, at least since
biblical times, the potential to experience years of plenty
followed by years of famine—interannual climate
variability—has been a major issue for societies. Climatic
variations have contributed to the rise and fall of societies
throughout human history.
People can respond to climate in several ways. At the most
general level, people adapt to the average or mean climate of the
region in which they live, on the assumption that the average of
past experience is the best guide to the future. Thus, people in
desert regions develop irrigation, design housing, and adapt their
lifestyles to cope with the hot, dry conditions they routinely
expect. Farmers choose crops appropriate to the average local
climate and its usual variability and develop agricultural
calendars that give a recommended day for planting. People also
respond to observed conditions of climate and weather after the
fact. Farmers wait to plant until the rains actually begin or apply
more irrigation on hot days. Households adjust home heating and air
conditioning in response to observed temperature and humidity. And
people respond to forecasts, both of weather and of climate, with a
range of anticipatory actions that depend on the lead time and
reliability of the forecast. A farmer may decide not to plant at
all if a drought is forecast; a water manager may adjust plans for
reservoir control.
In responding to climate, people may act both to minimize the
risk of hazardous climate and to capitalize on climatic
opportunities. Flood-
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control dams, for example, minimize the risk of floods and also
enable farming to take advantage of abundant sunshine and warmth in
a dry growing season by adding stored water from previous, wetter
seasons.
People have always sought the ability to predict the weather and
climate in the belief that this ability would bring great benefits.
Developments in weather forecasting over the past few decades have
confirmed this belief. It is now possible, for example, to warn
human populations about approaching hurricanes and tornadoes and
thereby greatly reduce loss of life from these extreme weather
events. Weather information can now be arrayed in forms that enable
decision makers to fine-tune activities so as to get the best
possible outcomes from the weather conditions they experience. The
focus of this book is on how to achieve similar benefits from the
recent impressive advances in understanding the mechanisms that
regulate climatic variability on seasonal-to-interannual time
scales in many tropical and some temperate regions and in
skillfully forecasting climate on these time scales.
Use of Climate Knowledge to Improve
Well-Being
Climatic resources are exploited best by human beings when human
activities are attuned to the types of climatic variations (mean
conditions, seasonal-to-interannual variability, and the frequency
and magnitude of extreme events) that affect their outcomes.
Although human societies are not perfectly attuned to the seasonal
and interannual rhythms and anomalies of climate, societies have
co-evolved with local climatic resources to the point that our
species generally copes well with a range of expected climatic
conditions. Humanity has developed a variety of coping systems that
function within individuals, small groups, firms, industries,
societies, and governments. At the individual level, people keep
coats and umbrellas handy if they live in climates that get cold
and rainy. Farmers grow a mix of crops that has proven profitable
over the long run under expected climate conditions that include
some outstanding years, some bad ones, and a lot in between.
Engineers design a certain amount of excess capacity into reservoir
operations to take account of natural variability in precipitation
and thus are able to meet demands for water under most climate
conditions. At the group level, many communities develop norms that
require the sharing of resources to help those harmed by extreme
climatic events.
Human beings also adjust their societies to the risks of a
variable climate and codify these responses in human institutions.
Nomadic pastoralism provides a basis of subsistence and a structure
for society for some human groups living in climates with scarce
and highly variable precipitation. When moisture is too scarce in
one location, people move
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to locations where it is adequate to produce required supplies
of food and fiber. Early agricultural societies like those of the
Nile delta were built around seasonal variations in water flow,
which affected their technology, their social organization, and
even their religious beliefs. In many modern societies, a hazard
insurance industry and programs of disaster transfer payments from
government have arisen to help offset social and economic loss from
the extreme weather conditions that are part of a variable
climate.
Knowledge about climate is used not only to respond to extreme
events—by reducing risk and exploiting climatic
"windfalls"—but also to make minor adjustments to improve
efficiency when variations are less extreme. In the United States,
for example, an entire industry of consulting climatologists has
developed to provide tailored climatic information routinely to
clients in sectors such as the hydroelectric power industry, which
can use this information to make incremental adjustments to
planning and operations.
When Climate Becomes Hazardous
Climate does not always stay within the limits that social
institutions plan for, and human adjustment is not perfect.
One-hundred-year floods occasionally occur in consecutive years in
the same watershed. Killing frosts occurring days, even weeks,
after the "95 percent probability of last frost date" may happen
two years in three. In such situations, when conditions fall
outside the range of the expected, climate can become a hazard. An
additional recent concern is the possibility that global climate
change may increase the frequency or magnitude of extreme climatic
events such as heat waves and major storms, making the systems that
societies have put in place to cope with such events no longer
adequate.
Climatic hazards come in many forms, from rapid-onset,
short-lived events such as hurricanes, hail storms, and blizzards
to slow-onset, long-lived fluctuations such as droughts. When
climatic knowledge is poor, preparedness is low, and coping systems
inadequate, climatic hazards exact severe social, economic, and
environmental costs. By the same token, departure from normal
climatic conditions can create new opportunities to be
exploited.
Climate Sensitivity and
Vulnerability
The sensitivity of human well-being to climatic variation is the
extent to which important outcomes change as a function of that
variation. Sensitivity is mainly indirect, in that climatic effects
on human health and socioeconomic systems are in large part
mediated by climate-sensitive
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biophysical systems. For example, human nutrition is sensitive
to climate mainly because crop production is sensitive to climate,
and crop production is sensitive because of climatic effects on
such factors as local rainfall and the spread of crop pests and
diseases. So both biophysical and socioeconomic systems may be
sensitive to climate, and many of the socioeconomic effects are due
in part to the biophysical ones.
The human consequences of climatic variation depend on the
behavior of social systems as well as on biophysical events. To the
extent that a society or social group understands or accurately
anticipates climatic events and their biophysical effects, it may
be able to buffer the negative effects of these events and take
advantage of climatic opportunities, thus decreasing sensitivity on
the downside while exploiting it on the upside. Modern production
agriculture and those whose livelihoods depend on it remain
sensitive to variability in temperature and precipitation despite
decades of technical and social innovation aimed at reducing
sensitivity by controlling access to water; limiting infestations
of pests, weeds, and diseases; insuring against catastrophic loss;
developing drought-tolerant and disease-resistant seed varieties;
and the like.
Often sensitivity is greatest at ecological, economic, and
social margins. Faunal and floral communities in areas straddling
the margins (boundaries) of ecosystems—natural and
managed—are less stable with respect to climate variability
than communities safely in the interiors (Blaikie and Brookfield,
1987). Similarly, the poor, the elderly, the infirm, and other
marginal segments of society often bear a disproportionate share of
the total social costs of climatic variability (Blaikie and
Brookfield, 1987). In such cases, a relatively minor climatic
fluctuation may cause disproportionately large consequences. With
appropriate policies in place, the most affected groups may
therefore gain great benefits from the use of climate
forecasts.
Our definition of sensitivity includes human efforts to adapt to
climate in that it refers to outcomes after taking into account
things people do to cope with expected climatic variations. This
definition contrasts with that employed by some other writers,
whose concept of sensitivity presumes that the human consequences
of climatic events can be meaningfully analyzed independently of
adaptive behavior. We do not find this approach useful because, as
we elaborate in Chapter 3, human societies, and particularly the
conduct of weather-sensitive activities, has coevolved with climate
and has always included a range of adaptive strategies. Thus,
sensitivity—a measure of the functional relationship between
climatic events and human outcomes—is a property of human
groups or activities that have particular adaptations in place.
Changing the adaptations can change sensitivity.
We use the term "vulnerable" to refer to human groups or
activities
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that face the risk of extreme negative outcomes as a result of
climatic events that overwhelm the adaptations they have in place.
Vulnerability, like sensitivity, is a function of both climatic
events and human adaptation. We use separate terms to reflect the
special importance most societies give to the risk of catastrophic
(i.e., extreme negative) outcomes. It is important to recognize
that, as with sensitivity, human activities can increase or
decrease vulnerability. For instance, urban development in
hurricane-prone coastal areas increases the risk from hurricanes
even when the frequency of hurricane events remains unchanged.
Increasing population and affluence in the arid western United
States have stimulated rising demand for essentially fixed water
supplies; this has increased the risk from drought apart from
fluctuations in precipitation. Systems of flood-control dams
decrease vulnerability to flood damage from most major storms, but
they may increase the damage caused by the most extreme ones.
Actions that affect the distribution of income also affect the
vulnerability of human populations to extreme negative climatic
events by altering the resources people have to prepare and
respond.
Sensitivity and vulnerability to climate variability constantly
change over time. Some reduction or increase in sensitivity, and
particularly in vulnerability to extreme events, may be the
unintended result of fundamental structural social changes
accompanying social development. For example, as the general level
of affluence and technological sophistication rises in a developing
country, changes in food preferences (for example, wheat over
millet, meat over grain) may lessen (or strengthen) dependence on
resources that are directly affected by seasonal-to-interannual
climate variability. As people depend increasingly on world markets
for food, their well-being becomes less sensitive to local climate
variations, but perhaps more sensitive to distant climatic events
that may threaten their supply lines.
The Potential Usefulness of Climate
Forecasts
Climate forecasting can benefit people by allowing them to
change the things they do to anticipate climatic events, thus
reducing their sensitivity to negative events and perhaps
increasing their sensitivity to positive events. The potential
value of skillful climate forecasts may or may not be greatest in
those regions where the predictive skill is the greatest. The
greatest value may be found in the regions where climate
variability has the largest economic impacts (positive or
negative), or where vulnerability is greatest and adequate coping
mechanisms can be provided. In regions where impact or
vulnerability is very large, even a small increase in forecast
skill may be of great value, even if the predictions are not as
certain as in other regions. Therefore, a focus on improving
forecast skill
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for those regions where the physical links are strongest may
provide the highest scientific payoff, but it may not provide the
most significant economic or humanitarian payoffs. Such
considerations may imply that there is much to be gained by
shifting some predictive effort from regions such as Latin America
and Southern Africa that are highly sensitive to the El
Niño/Southern Oscillation (ENSO) phenomenon to regions such
as Europe and West Africa, where outcomes may be highly sensitive
to Atlantic climate variability or to monsoon predictions for Asia,
even though predictive skill is currently very limited.
Improvements in the skill of forecasts, combined with the
expectation that the new knowledge will not be used with perfect
efficiency, means that it may be possible to deliver forecast
information in ways that lead human groups to cope more effectively
with seasonal-to-interannual climatic variability, reduce
sensitivity to the downside of climatic variation, and take better
advantage of climatic opportunities.
Therein lies the crux of our concerns here. The eventual value
of improved forecasting skill will depend on how people and
organizations deal with the new kind of information. Are they
likely to pay attention to it? Will they understand what the
climate models mean for them? Will they trust the messengers? How
will mass media organizations and other messengers transmit
forecast information, and how will their messages be interpreted?
Are recipients likely to systematically misinterpret the
information given to make it conform to their preexisting ideas?
How will they respond to the false alarms and false reassurances
that any imperfect forecasting system sometimes produces and to the
inevitable simplifications offered by mass media and other
messengers? And what can be done to transform potentially useful
forecasts into information that is actually used to benefit
society?
Structure Of This Book
This book examines the state of knowledge and the needs for
further knowledge relevant to understanding the effects of
seasonal-to-interannual climate forecasts and making them more
useful. Chapter 2 examines the current state of scientific
capability to make skillful climate forecasts on a
seasonal-to-interannual time scale and begins to address the
question of what it would take to make such forecasts more useful.
The information on climate forecasting is meant primarily as
background for those outside the forecasting community; the section
on usable knowledge is addressed both to forecasters and other
readers. Chapter 3 considers what is known about the strategies
people and societies have developed to cope with two qualities of
their environments: that climate is variable, and that (until
recently) climate variations have been essentially
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unpredictable. It summarizes the state of knowledge about the coping strategies used in specific climate-sensitive human activities and about human institutions, such as disaster insurance and emergency preparedness, that have developed to help cope with climatic variations.
Chapter 4 takes up the question, critical for making climate forecasts more useful, of how individuals and organizations are likely to respond, and how they might be led to respond more effectively, to the information in climate forecasts. It considers the ways in which climate forecast information might be useful and then considers available sources of information on how the coping systems people have developed for climate variability might respond to new information. These include actual responses to recent climate forecasts; research on how people assimilate information generally; and past experience with efforts to provide other kinds of scientific and technical information that people might use to improve their well-being, including information on practices to promote personal health and information from hazard warning systems. The chapter concludes by summarizing the state of knowledge and some promising hypotheses about how individuals and institutions are likely to respond to climate forecast information and how to make these responses more effective.
Chapter 5 examines the state of concept, methods, data, and knowledge that could be used to measure the human effects of climatic variability and the potential and actual benefits of skillful climate forecasts. It presents a conceptual framework and raises several issues that must be addressed to make such measurements, summarizes the state of scientific efforts to estimate the effects of climatic variations and the benefits of forecasts, and presents the panel's findings on these issues.
Finally, Chapter 6 summarizes the findings of the study and identifies a dozen scientific priorities—sets of research questions that, if pursued, will yield progress toward the ultimate goals of understanding and increasing the social value of seasonal-to-interannual climate forecasts. The questions fall into three broad categories: research on the potential benefits of climate forecast information, on improved dissemination of forecast information, and on estimating the consequences of climatic variations and of climate forecasts.
Representative terms from entire chapter:
climatic events
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