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Scientific-Technical Analyses of Impacts, Adaptations, and Mitigation of Climate Change

3.3. Food and Fiber

Agriculture. Crop yields and changes in productivity due to climate change will vary considerably across regions and among localities, thus changing the patterns of production. Productivity is projected to increase in some areas and decrease in others, especially the tropics and subtropics (Table 2). However, existing studies show that on the whole global agricultural production could be maintained relative to baseline production in the face of climate change modeled by general circulation models (GCMs) at doubled equivalent-CO2 equilibrium conditions, but that regional effects would vary widely. This conclusion takes into account the beneficial effects of CO2 fertilization, but does not allow for changes in agricultural pests and the possible effects of changing climatic variability.

term. The exact timing and extent of this pattern is uncertain. Climate and land-use impacts on the production of temperate forest products are expected to be relatively small. In tropical regions, the availability of fores: products is projected to decline by about half for non-climatic reasons related to human activities.

Fisheries. Climate-change effects interact with those of pervasive overfishing, diminishing nursery areas, and extensive inshore and coastal pollution. Globally, marine fisheries production is expected to remain about the same; high-latitude freshwater and aquaculture production are likely to increase, assuming that natural climate variability and the structure and strength of ocean currents remain about the same. The principal impacts will be felt at the national and local levels as species mix and centers of production shift. The positive effects of climate change-such as longer growing seasons, lower natural winter mortality, and faster growth rates in higher latitudes-may be offset by negative factors such as changes in established reproductive patterns, migration routes, and ecosystem relationships.

Focusing on global agricultural production does not address the
potentially serious consequences of large differences at local and
regional scales, even at mid-latitudes. There may be increased
risk of hunger and famine in some locations; many of the world's
poorest people-particularly those living in subtropical and
tropical areas, and dependent on isolated agricultural systems in
semi-arid and arid regions are most at risk of increased hunger. 3.4.
Many of these at-risk populations are found in sub-Saharan
Africa; south, east, and southeast Asia; and tropical areas of
Latin America, as well as some Pacific island nations.

Adaptation-such as changes in crops and crop varieties, improved water-management and irrigation systems, and changes in planting schedules and tillage practices-will be important in limiting negative effects and taking advantage of beneficial changes in climate. The extent of adaptation depends on the affordability of such measures, particularly in developing countries; access to know-how and technology; the rate of climate change; and biophysical constraints such as water availability, soil characteristics, and crop genetics. The incremental costs of adaptation strategies could create a serious burden for developing countries; some adaptation strategies may result in cost savings for some countries. There are significant uncertainties about the capacity of different regions to adapt successfully to projected climate change.

Livestock production may be affected by changes in grain prices and rangeland and pasture productivity. In general, analyses indicate that intensively managed livestock systems have more potential for adaptation than crop systems. This may not be the case in pastoral systems, where the rate of technology adoption is slow and changes in technology are viewed as risky. Forest Products. Global wood supplies during the next century may become increasingly inadequate to meet projected consumption due to both climatic and non-climatic factors. Boreal forests are likely to undergo irregular and large-scale losses of living trees because of the impacts of projected climate change. Such losses could initially generate additional wood supply from salvage harvests, but could severely reduce standing stocks and wood-product availability over the long

Human Infrastructure

Climate change and resulting sea-level rise can have a number of negative impacts on energy, industry, and transportation infrastructure; human settlements; the property insurance industry; tourism; and cultural systems and values.

In general, the sensitivity of the energy, industry, and transportation sectors is relatively low compared to that of agricultural or natural ecosystems, and the capacity for adaptation through management and normal replacement of capital is expected to be high. However, infrastructure and activities in these sectors would be susceptible to sudden changes, surprises, and increased frequency or intensity of extreme events. The subsectors and activities most sensitive to climate change include agroindustry, energy demand, production of renewable energy such as hydroelectricity and biomass, construction, some transportation activities, existing flood mitigation structures, and transportation infrastructure located in many areas, including vulnerable coastal zones and permafrost regions.

Climate change clearly will increase the vulnerability of some coastal populations to flooding and erosional land loss. Estimates put about 46 million people per year currently at risk of flooding due to storm surges. This estimate results from multiplying the total number of people currently living in areas potentially affected by ocean flooding by the probability of flooding at these locations in any year, given the present protection levels and population density. In the absence of adaptation measures, a 50-cm sea-level rise would increase this number to about 92 million; a 1-m sealevel rise would raise it to 118 million. If one incorporates anticipated population growth, the estimates increase substantially. Some small island nations and other countries will confront greater vulnerability because their existing sea and

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Scientific-Technical Analyses of Impacts, Adaptations, and Mitigation of Climate Change

Table 2: Selected crop study results for 2 x CO2-equivalent equilibrium GCM scenarios.

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Note: For most regions, studies have focused on one or two principal grains. These studies strongly demonstrate the variability in estimated yield impacts among countries, scenarios, methods of analysis, and crops, making it difficult to generalize

Scientific-Technical Analyses of Impacts, Adaptations, and Mitigation of Climate Change

coastal defense systems are less well-established. Countries with higher population densities would be more vulnerable. For these countries, sea-level rise could force internal or international migration of populations.

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could economically weaken other sectors, such as banking. The insurance industry currently is under stress from a series of "billion dollar" storms since 1987, resulting in dramatic increases in losses, reduced availability of insurance, and higher costs. Some in the insurance industry perceive a current trend toward increased frequency and severity of extreme climate events. Examination of the meteorological data fails to support this perception in the context of a long-term change, although a shift within the limits of natural variability may have occurred. Higher losses strongly reflect increases in infrastructure and economic worth in vulnerable areas as well as a possible shift in the intensity and frequency of extreme weather events.

A number of studies have evaluated sensitivity to a 1-m sea-
level rise. This increase is at the top of the range of IPCC
Working Group I estimates for 2100; it should be noted, how-
ever, that sea level is actually projected to continue to rise
beyond 2100. Studies using this 1-m projection show a partic-
ular risk for small islands and deltas. Estimated land losses
range from 0.05% for Uruguay, 1% for Egypt, 6% for the
Netherlands, and 17.5% for Bangladesh to about 80% for the
Majuro Atoll in the Marshall Islands, given the present state of
protection systems. Large numbers of people also are affect- 3.5.
ed-for example, about 70 million each in China and
Bangladesh. Many nations face lost capital value in excess of
10% of their gross domestic product (GDP). Although annual
protection costs for many nations are relatively modest (about
0.1% of GDP), the average annual costs to many small island
states total several percent of GDP. For some island nations,
the high cost of providing storm-surge protection would make
it essentially infeasible, especially given the limited availabili-
ty of capital for investment.

The most vulnerable human settlements are located in damage-prone areas of the developing world that do not have the resources to cope with impacts. Effective coastal-zone management and land-use regulation can help direct population shifts away from vulnerable locations such as flood plains, steep hillsides, and lowlying coastlines. One of the potentially unique and destructive effects on human settlements is forced internal or international migration of populations. Programs of disaster assistance can offset some of the more serious negative consequences of climate change and reduce the number of ecological refugees.

Property insurance is vulnerable to extreme climate events. A higher risk of extreme events due to climate change could lead to higher insurance premiums or the withdrawal of coverage for property in some vulnerable areas. Changes in climate variability and the risk for extreme events may be difficult to detect or predict, thus making it difficult for insurance companies to adjust premiums appropriately. If such difficulty leads to insolvency, companies may not be able to

CLIMATE
CHANGE:
TEMPERATURE,
PRECIPITATION,
AND WEATHER

Human Health

Climate change is likely to have wide-ranging and mostly adverse impacts on human health, with significant loss of life. These impacts would arise by both direct and indirect pathways (Figure 3), and it is likely that the indirect impacts would, in the longer term, predominate.

Direct health effects include increases in (predominantly cardiorespiratory) mortality and illness due to an anticipated increase

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honor insurance contracts, which Figure 3: Ways in which climate change can affect human health.

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Scientific-Technical Analyses of Impacts, Adaptations, and Mitigation of Climate Change

in the intensity and duration of heat waves. Temperature increases in colder regions should result in fewer cold-related deaths. An increase in extreme weather would cause a higher incidence of death, injury, psychological disorders, and exposure to contaminated water supplies.

Indirect effects of climate change include increases in the potential transmission of vector-borne infectious diseases (e.g., malaria, dengue, yellow fever, and some viral encephalitis) resulting from extensions of the geographical range and season for vector organisms. Projections by models (that entail necessary simplifying assumptions) indicate that the geographical zone of potential malaria transmission in response to world temperature increases at the upper part of the IPCC-projected range (3-5°C by 2100) would increase from approximately 45% of the world population to approximately 60% by the latter half of the next century. This could lead to potential increases in malaria incidence (on the order of 50-80 million additional annual cases, relative to an assumed global background total of 500 million cases), primarily in tropical, subtropical, and less well-protected temperate-zone populations. Some increases in non-vector-borne infectious diseases

such

as salmonellosis, cholera, and giardiasis—also could occur as a result of elevated temperatures and increased flooding.

that accelerate technology development, diffusion, and transfer in all sectors including the energy, industry, transportation, residential/commercial, and agricultural/forestry sectors. By the year 2100, the world's commercial energy system in effect will be replaced at least twice, offering opportunities to change the energy system without premature retirement of capital stock; significant amounts of capital stock in the industrial, commercial, residential, and agricultural/forestry sectors will also be replaced. These cycles of capital replacement provide opportunities to use new, better performing technologies. It should be noted that the analyses of Working Group II do not attempt to quantify potential macroeconomic consequences that may be associated with mitigation measures. Discussion of macroeconomic analyses is found in the IPCC Working Group III contribution to the Second Assessment Report. The degree to which technical potential and cost-effectiveness are realized is dependent on initiatives to counter lack of information and overcome cultural, institutional, legal, financial and economic barriers that can hinder diffusion of technology or behavioral changes. The pursuit of mitigation options can be carried out within the limits of sustainable development criteria. Social and environmental criteria not related to greenhouse gas emissions abatement could, however, restrict the ultimate potential of each of the options.

Additional indirect effects include respiratory and allergic dis-
orders due to climate-enhanced increases in some air pollu- 4.1.
tants, pollens, and mold spores. Exposure to air pollution and
stressful weather events combine to increase the likelihood of
morbidity and mortality. Some regions could experience a
decline in nutritional status as a result of adverse impacts on
food and fisheries productivity. Limitations on freshwater sup-
plies also will have human health consequences.

Quantifying the projected impacts is difficult because the
extent of climate-induced health disorders depends on numer-
ous coexistent and interacting factors that characterize the vul-
nerability of the particular population, including environmen-
tal and socioeconomic circumstances, nutritional and immune
status, population density, and access to quality health care ser-
vices. Adaptive options to reduce health impacts include pro-
tective technology (e.g., housing, air conditioning, water
purification, and vaccination), disaster preparedness, and
appropriate health care.

Options to Reduce Emissions and Enhance
Sinks of Greenhouse Gases

Human activities are directly increasing the atmospheric concentrations of several greenhouse gases, especially CO2, CH4, halocarbons, sulfur hexafluoride (SF), and nitrous oxide (N2O). CO2 is the most important of these gases, followed by CH. Human activities also indirectly affect concentrations of water vapor and ozone. Significant reductions in net greenhouse gas emissions are technically possible and can be economically feasible. These reductions can be achieved by utilizing an extensive array of technologies, and policy measures

Energy, Industrial Process, and
Human Settlement Emissions

Global energy demand has grown at an average annual rate of approximately 2% for almost 2 centuries, although energy demand growth varies considerably over time and between different regions. In the published literature, different methods and conventions are used to characterize energy consumption. These conventions differ, for example, according to their definition of sectors and their treatment of energy forms. Based on aggregated national energy balances, 385 EJ of primary energy was consumed in the world in 1990, resulting in the release of 6 Gt C as CO2. Of this, 279 EJ was delivered to end users, accounting for 3.7 Gt C emissions as CO2 at the point of consumption. The remaining 106 EJ was used in energy conversion and distribution, accounting for 2.3 Gt C emissions as CO2. In 1990, the three largest sectors of energy consumption were industry (43% of total CO, releases), residential/commercial buildings (28%), and transport (22%). Of these, transport sector energy use and related CO2 emissions have been the most rapidly growing over the past 2 decades. For the detailed sectoral mitigation option assessment in this report, 1990 energy consumption estimates are based on a range of literature sources; a variety of conventions are used to define these sectors and their energy use, which is estimated to amount to a total of 259-282 EJ.

Figure 4 depicts total energy-related emissions by major world region. Organisation for Economic Cooperation and Development (OECD) nations have been and remain major energy users and fossil fuel CO2 emitters, although their share of global fossil fuel carbon emissions has been declining.

Scientific-Technical Analyses of Impacts, Adaptations, and Mitigation of Climate Change

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Figure 4: Global energy-related CO2 emissions by major world region in Gt C/yr (Marland et al., 1994; Grübler and Nakicenovic, 1992; Etemand and Luciani, 1991; Fujii, 1990; UN, 1952). Note that CPA = Centrally Planned Asia and PAO = Pacific and Oceania.

Developing nations, taken as a group, still account for a smaller portion of total global CO2 emissions than industrialized nations OECD and former Soviet Union/Eastern Europe (FSU/EE) but most projections indicate that with forecast rates of economic and population growth, the future share of developing countries will increase. Future energy demand is anticipated to continue to grow, at least through the first half of the next century. The IPCC (1992, 1994) projects that without policy intervention, there could be significant growth in emissions from the industrial, transportation, and commercial/residential buildings sectors.

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transfer, as well as measures to overcome a variety of non-technical barriers. The potential for greenhouse gas emission reductions exceeds the potential for energy use efficiency because of the possibility of switching fuels and energy sources. Because energy use is growing world-wide, even replacing current technology with more efficient technology could still lead to an absolute increase in CO2 emissions in the future.

In 1992, the IPCC produced six scenarios (IS92a-f) of future energy use and associated greenhouse gas emissions (IPCC, 1992, 1995). These scenarios provide a wide range of possible future greenhouse gas emission levels, without mitigation measures.

In the Second Assessment Report, future energy use has been reexamined on a more detailed sectoral basis, both with and without new mitigation measures, based on existing studies. Despite different assessment approaches, the resulting ranges of energy consumption increases to 2025 without new measures are broadly consistent with those of IS92. If past trends continue, greenhouse gas emissions will grow more slowly than energy use, except in the transport sector.

The following paragraphs summarize energy-efficiency improvement potentials estimated in the IPCC Second

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