• GG 312: Global Climate Change and Environmental Impacts (Fall 2002)


    Chapter 8: Impacts, Adaptations and Mitigation of Climate Change

    8.1. Impacts: Water Resources
    8.2. Impacts: Agriculture and Food Security
    8.3. Impacts: Terrestrial and Freshwater Ecosystems
    8.4. Impacts: Coastal Zones and Marine Ecosystems
    8.5. Impacts: Human Settlements, Energy and Industry
    8.6. Impacts: Insurance and Financial Services
    8.7. Impacts: Human Health
    8.8. Impacts: Sea Level Rise
    8.9. Options to Reduce Emissions and Enhance Sinks of GHG
    8.9.A. Energy, Industrial and Residential Emissions
    8.9.B. Agriculture, Rangelands and Forestry
    8.9.C Policy Instruments

    Human activities are increasing the atmospheric concentrations of greenhouse gases - which tend to warm the atmosphere - and, in some regions, aerosols - which tend to cool the atmosphere. Climate models, taking into account greenhouse gases and aerosols, project an increase in global mean surface temperature of about 2.5 tdeg C by 2100, and an associated increase in sea level of about 14 to 70 cm. The reliability of regional-scale predictions is still low, and the degree to which climate variability may change is uncertain. However, potentially serious changes have been identified, including an increase in some regions in the incidence of extreme high-temperature events, floods, and droughts, with resultant consequences for fires, pest outbreaks, and ecosystem composition, structure, and functioning, including primary productivity.

    Policy makers are faced with responding to the risks posed by anthropogenic emissions of greenhouse gases in the face of significant scientific uncertainties. Policymakers will have to decide to what degree they want to take precautionary measures by mitigating greenhouse gas emissions and enhancing the resilience of vulnerable systems by means of adaptation.

    Options for adapting to change or mitigating change that can be justified for other reasons today (e.g., abatement of air and water pollution) and make society more flexible or resilient to anticipated adverse effects of climate change appear particularly desirable.

    8.1. Impacts: Water Resources

    • There are apparent trends in streamflow volumes - increases and decreases - in many regions. Peak streamflow will move from spring to winter in many areas because with warming a greater proportion of winter precip falls as rain.
    • Flood magnitude and frequency are likely to increase in most regions as a consequence of increase in the frequency of heavy precip events.
    • Climate change challenges existing water resources management by adding uncertainty. One-third of the world's population (1.7 billion people) presently live in countries that are water-stressed. This number is projected to increase to about 5 billion by 2025.

    8.2. Impacts: Agriculture and Food Security

    • The response of crop yields to climate change varies widely, depending on the species, cultivar, soil conditions, treatment of CO2 direct effects, etc.
    • Degradation of soil and water resources is one of the major future challenges for global agriculture.
    • Most studies indicate that mean annual temperature increases of 2.5 degrees C or greater would prompt food prices to increase as a result of slowing in the expansion of global food capacity relative to demand.
    • The impacts of climate change on agriculture are estimated to result in small percentage changes in global income, with positive changes in more developed regions and smaller or negative changes in developing regions.

    8.3. Impacts: Terrestrial and Freshwater Ecosystems

    • Increasing CO2 concentration would increase net primary productivity whereas increasing temperatures may have positive or negative effects.
    • In arid or semi-arid regions (namely, rangelands, woodlands and dry forests), where climate change is likely to decrease available soil moisture, productivity is expected to decrease.
    • Climate change will lead to poleward movement of the southern and norther boundaries of fish distributions, loss of habitat for cold and coolwater fish and and gain in habitat for warmwater fish.

    8.4. Impacts: Coastal Zones and Marine Ecosystems

    • Climate change will result in increased sea surface temperature and sea level; decreases in sea-ice cover and changes in salinity and ocean circulation.
    • If warm events (El Ninos) increase in frequency, plankton biomass and fish larvae abundance would decline and advsersly impact fish, marine mammals, seabirds, etc.
    • Low-latitude tropical and subtropical coastlines, where there is pressure from human population, are particularly susceptible to climate change impacts.
    • Coastal ecosystems such as coral reefs, salt marshes, mangrove forests, etc. will be impacted by sea-level rise, warming SSTs and any changes in storm frquency and intensity.

    8.5. Impacts: Human Settlements, Energy and Industry

    • Economic sectors that support the settlement are affected because of changes in productive capacity (eg., agriculture or fisheries) or changes in market demand for goods and services produced there.
    • Some aspects of physical infrastructure (including energy transmission and distribution systems), buildings, urban services (including transportation) and specific industries (tourism, construction, etc.) may be affected.
    • Population may be affected through extreme weather, changes in health status, or migration. The most widespread serious potential impacts are flooding, landslides, mudslides and avalanches, driven by projected increases in rainfall intensity and sea level rise.

    8.6. Impacts: Insurance and Financial Services

    • The costs of extreme weather events have exhibited a rapid upward trend in recent decades.
    • Part of the observed upward trend in disaster losses is linked to socio-economic factors - population growth, increased wealth, urbanization in vulnerable areas - and part is linked to climatic factors such as changes in precip, flooding and drought events.
    • Weather and climate related losses can stress insurance companies to the point of impaired profitability, consumer price increases, withdrawl of coverage etc.

    8.7. Impacts: Human Health

    • There is evidence of human health sensitivity to climate, particularly for mosquito-borne diseases.
    • If heat waves increase in frequency and intensity, the risk of death and serious illness would increase, principally in older age groups and the urban poor.
    • Climate change will decrease air quality in urban areas with air pollution problems.
    • Changes in food supply resulting from climate change could affect the nutrition and health of the poor in some regions of the world.

    8.8. Impacts: Sea Level Rise

    • The rate of global average sea level rise during the 20th century is in the range 1.0 to 2.0 mm/yr, with a central value of 1.5 mm/yr.
    • The average rate of sea level rise has been larger during the 20th century than the 19th century· No significant acceleration in the rate of sea level rise during the 20th century has been detected.
    • Ocean thermal expansion leads to an increase in ocean volume at constant mass. Observational estimates of about 1 mm/yr over recent decades are similar to values of 0.7 to 1.1 mm/yr obtained from AOGCMs over a comparable period.
    • The mass of the ocean, and thus sea level, changes as water is exchanged with glaciers and ice caps. Observational and modelling studies of glaciers and ice caps indicate a contribution to sea level rise of 0.2 to 0.4 mm/yr averaged over the 20th century.
    • Projections of components contributing to sea-level change from 1990 to 2100 using a range of AOGCMs following the IS92a scenario, we obtain a range of global-average sea-level rise from 0.14 to 0.70 m. This range reflects systematic uncertainties in modelling.

    8.9 Options to Reduce Emissions and Enhance Sinks of GHG

    Human activities are directly increasing the atmospheric concentrations of several greenhouse gases, especially CO2, CH4, halocarbons, sulfur hexafluoride (SF6), and nitrous oxide (N2O). CO2 is the most important of these gases, followed by CH4. 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.

    8.9.A. Energy, Industrial and Residental Emissions

    Global energy demand has frown at an average annual rate of approximately 2% for almost 2 centuries, although energy demand growth varies considerably over time and between different regions. 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 as CO2. In 1990, the three largest sectors of energy consumption were industry (45% of total CO2 releases), residential/commercial sector (29%), and transport (21%). Future energy demand is anticipated to continue to grow, at least through the first half of the next century.

    1 EJ (Exa Joule) = 1018 J

    Energy Demand: Numerous studies have indicated that 10 to 30 % energy-efficiency gains above present levels are feasible at little or no net cost in many parts of the world through technological conservation measures and improved management practices over the next 2 to 3 decades.

    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.

    Industry: Energy use in 1990 was estimated to be 98 to 117 EJ, and is projected to grow to 140 to 242 EJ in 2025 without new measures. Industrial sector energy-related greenhouse gas emissions in most industrialized countries are expected to be stable or decreasing as a result of industrial restructuring and technological innovation, whereas industrial emissions in developing countries are projected to increase mainly as a result of industrial growth.

    Technologies and measures for reducing energy-related emissions from this sector include improving efficiency (e.g., energy and materials savings, cogeneration, energy cascading, steam recovery, and use of more efficient motors and other electrical devices); recycling materials and switching to those with lower greenhouse gas emissions; and developing processes that use less energy and materials.

    Transportation: Energy use in 1990 was estimated to be 61-65 EJ, and is projected to grow to 90-140 EJ in 2025 without new measures. Projected energy use in 2025 could be reduced by about a third to 60-100 EJ through vehicles using very efficient drive-trains, lightweight construction, and low air-resistance design, without compromising comfort and performance. Further energy-use reductions are possible through the use of smaller vehicles; altered land-use patterns, transport systems, mobility patterns, and lifestyles; and shifting to less energy-intensive transport modes.

    Commercial/Residential Sector: Energy use in 1990 was estimated to be about 100 EJ, and is projected to grow to 165-205 EJ in 2025 without new measures. Projects energy use could be reduced by about a quarter to 126-170 EJ by 2025 without diminishing services through the use of energy efficient technology.

    Technical changes might include reduced heat transfers through building structures and more efficient space-conditioning and water supply systems, lighting, and appliances. Ambient temperatures in urban areas can be reduced through increased vegetation and greater reflectivity of building surfaces, reducing the energy required for space conditioning.

    Mitigating Industrial Process and Human Settlement Emissions: Large reductions are possible in some cases. Measures include modifying production processes, eliminating solvents, replacing feed stocks, materials substitution, increased recycling, and reduced consumption of greenhouse gas-intensive materials.

    Energy Supply: This assessment focuses on new technologies for capital investment and not on potential retrofitting of existing capital stock to use less carbon-intensive forms of primary energy.

    Greenhouse gas reductions in the use of fossil fuels:

    • More Efficient Conversion of Fossil Fuels: The efficiency of power production can be increased from the present world average of about 30% to more than 60% in the longer term.
    • Switching to Low-Carbon Fossil Fuels and Suppressing Emissions: Switching from coal to oil or natural gas, and from oil to natural gas, can reduce emissions. The lower carbon-containing fuels can, in general, be converted with higher efficiency than coal. Large resources of natural gas exist in many areas.
    • Decarbonization of Flue Gases and Fuels, and CO2 Storage: The removal and storage of CO2 from fossil fuel power-station stack gases is feasible, but reduces the conversion efficiency and significantly increases the production cost of electricity. For some longer term CO2 storage options, the costs, environmental effects, and efficacy of such options remain largely unknown.

    Switching to non-fossil fuel sources of energy:

    • Switching to Nuclear Energy: Nuclear energy could replace baseload fuel electricity generation in many parts of the world if generally acceptable responses can be found to concerns such as reactor safety, radioactive-waste transport and disposal, and nuclear proliferation.
    • Switching to Renewable Sources of Energy: Solar, biomass, wind, hydro, and geothermal technologies already are widely used. In 1990, renewable sources of energy contributed about 20% of the world's primary energy consumption, most of it fuelwood and hydropower.

    8.9.B. Agriculture, Rangelands, and Forestry

    Beyond the use of biomass fuels to displace fossil fuels, the management of forests, agricultural lands, and rangelands can play an important role in reducing current emissions of CO2, CH4, and N2O and in enhancing carbon sinks. A number of measures could conserve and sequester substantial amounts of carbon (approximately 60-90 Gt in the forestry sector alone) over the next 50 years.

    Factors affecting costs include opportunity costs of land; initial costs of planting and establishment; cost of nurseries; the cost of annual maintenance and monitoring; and transaction costs.

    Land use and management measures include -

    • Sustaining existing forest cover
    • Slowing deforestation
    • Regenerating natural forests
    • Establishing tree populations
    • Promoting agroforestry
    • Altering management of agricultural soils and rangelands
    • Improving efficiency of fertilizer use
    • Restoring degraded agricultural lands and rangelands
    • Recovering CH4 from stored manure
    • Improving the diet quality of ruminants

    8.9.C. Policy Instruments

    Mitigation depends on reducing barriers to the diffusion and transfer of technology, mobilizing financial resources, supporting capacity building in developing countries, and other approaches to assist in the implementation of behavioral changes and technological opportunities in all regions of the globe.

    Governments can choose policies that facilitate the penetration of less greenhouse gas-intensive technologies and modified consumption patterns. Indeed, many countries have extensive experience with a variety of policies that can accelerate the adoption of such technologies.

    Policies to reduce net greenhouse gas emissions appear more easily implemented when they are designed to address other concerns that impede sustainable development (e.g., air pollution and soil erosion). A number of policies, some of which may need regional or international agreement, including -

    • Putting in place appropriate institutional and structural frameworks
    • Energy pricing strategies (e.g., carbon or energy taxes, and reduced energy subsidies)
    • Reducing or removing other subsidies (e.g., agricultural and transport subsidies) that increase greenhouse gas emissions
    • Tradable emission permits
    • Voluntary programs and negotiated agreements with industry
    • Utility demand-size management programs
    • Regulatory programs, including minimum energy efficiency standards (e.g., forappliances and fuel economy)
    • Stimulating RD&D to make new technologies available
    • Market pull and demonstration programs that stimulate the development and application of advanced technologies
    • Renewable energy incentives during market build-up
    • Incentives such as provisions for accelerated depreciation and reduced costs for consumers
    • Education and training; information and advisory measures
    • Options that also support other economic and environmental goals.

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