IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Synthesis Report

4. Adaptation and mitigation options[14]

A wide array of adaptation options is available, but more extensive adaptation than is currently occurring is required to reduce vulnerability to climate change. There are barriers, limits and costs, which are not fully understood. {4.2}

Societies have a long record of managing the impacts of weather- and climate-related events. Nevertheless, additional adaptation measures will be required to reduce the adverse impacts of projected climate change and variability, regardless of the scale of mitigation undertaken over the next two to three decades. Moreover, vulnerability to climate change can be exacerbated by other stresses. These arise from, for example, current climate hazards, poverty and unequal access to resources, food insecurity, trends in economic globalisation, conflict and incidence of diseases such as HIV/AIDS. {4.2}

Some planned adaptation to climate change is already occurring on a limited basis. Adaptation can reduce vulnerability, especially when it is embedded within broader sectoral initiatives (Table SPM.4). There is high confidence that there are viable adaptation options that can be implemented in some sectors at low cost, and/or with high benefit-cost ratios. However, comprehensive estimates of global costs and benefits of adaptation are limited. {4.2, Table 4.1}

Table SPM.4. Selected examples of planned adaptation by sector. {Table 4.1}

Sector Adaptation option/strategy Underlying policy framework Key constraints and opportunities to implementation (Normal font = constraints; italics = opportunities
Water Expanded rainwater harvesting; water storage and conservation techniques; water re-use; desalination; water-use and irrigation efficiency National water policies and integrated water resources management; water-related hazards management Financial, human resources and physical barriers; integrated water resources management; synergies with other sectors  
Agriculture Adjustment of planting dates and crop variety; crop relocation; improved land management, e.g. erosion control and soil protection through tree planting R&D policies; institutional reform; land tenure and land reform; training; capacity building; crop insurance; financial incentives, e.g. subsidies and tax credits  Technological and financial constraints; access to new varieties; markets; longer growing season in higher latitudes; revenues from ‘new’ products  
Infrastructure/settlement (including coastal zones)  Relocation; seawalls and storm surge barriers; dune reinforcement; land acquisition and creation of marshlands/wetlands as buffer against sea level rise and flooding; protection of existing natural barriers Standards and regulations that integrate climate change considerations into design; land-use policies; building codes; insurance Financial and technological barriers; availability of relocation space; integrated policies and management; synergies with sustainable development goals  
Human health Heat-health action plans; emergency medical services; improved climate-sensitive disease surveillance and control; safe water and improved sanitation  Public health policies that recognise climate risk; strengthened health services; regional and international cooperation Limits to human tolerance (vulnerable groups); knowledge limitations; financial capacity; upgraded health services; improved quality of life 
Tourism Diversification of tourism attractions and revenues; shifting ski slopes to higher altitudes and glaciers; artificial snow-making  Integrated planning (e.g. carrying capacity; linkages with other sectors); financial incentives, e.g. subsidies and tax credits Appeal/marketing of new attractions; financial and logistical challenges; potential adverse impact on other sectors (e.g. artificial snow-making may increase energy use); revenues from ‘new’ attractions; involvement of wider group of stakeholders  
Transport Ralignment/relocation; design standards and planning for roads, rail and other infrastructure to cope with warming and drainage Integrating climate change considerations into national transport policy; investment in R&D for special situations, e.g. permafrost areas Financial and technological barriers; availability of less vulnerable routes; improved technologies and integration with key sectors (e.g. energy) 
Energy Strengthening of overhead transmission and distribution infrastructure; underground cabling for utilities; energy efficiency; use of renewable sources; reduced dependence on single sources of energy National energy policies, regulations, and fiscal and financial incentives to encourage use of alternative sources; incorporating climate change in design standards  Access to viable alternatives; financial and technological barriers; acceptance of new technologies; stimulation of new technologies; use of local resources  

Note: Other examples from many sectors would include early warning systems.

Adaptive capacity is intimately connected to social and economic development but is unevenly distributed across and within societies. {4.2}

A range of barriers limits both the implementation and effectiveness of adaptation measures. The capacity to adapt is dynamic and is influenced by a society’s productive base, including natural and man-made capital assets, social networks and entitlements, human capital and institutions, governance, national income, health and technology. Even societies with high adaptive capacity remain vulnerable to climate change, variability and extremes. {4.2}

Both bottom-up and top-down studies indicate that there is high agreement and much evidence of substantial economic potential for the mitigation of global GHG emissions over the coming decades that could offset the projected growth of global emissions or reduce emissions below current levels (Figures SPM.9, SPM.10).[15] While top-down and bottom-up studies are in line at the global level (Figure SPM.9) there are considerable differences at the sectoral level. {4.3}

Comparison between global economic mitigation potential and projected emissions increase in 2030


Figure SPM.9. Global economic mitigation potential in 2030 estimated from bottom-up (Panel a) and top-down (Panel b) studies, compared with the projected emissions increases from SRES scenarios relative to year 2000 GHG emissions of 40.8 GtCO2-eq (Panel c). Note: GHG emissions in 2000 are exclusive of emissions of decay of above ground biomass that remains after logging and deforestation and from peat fires and drained peat soils, to ensure consistency with the SRES emission results. {Figure 4.1}

Economic mitigation potentials by sector in 2030 estimated from bottom-up studies


Figure SPM.10. Estimated economic mitigation potential by sector in 2030 from bottom-up studies, compared to the respective baselines assumed in the sector assessments. The potentials do not include non-technical options such as lifestyle changes. {Figure 4.2}


a) The ranges for global economic potentials as assessed in each sector are shown by vertical lines. The ranges are based on end-use allocations of emissions, meaning that emissions of electricity use are counted towards the end-use sectors and not to the energy supply sector.

b) The estimated potentials have been constrained by the availability of studies particularly at high carbon price levels.

c) Sectors used different baselines. For industry, the SRES B2 baseline was taken, for energy supply and transport, the World Energy Outlook (WEO) 2004 baseline was used; the building sector is based on a baseline in between SRES B2 and A1B; for waste, SRES A1B driving forces were used to construct a waste-specific baseline; agriculture and forestry used baselines that mostly used B2 driving forces.

d) Only global totals for transport are shown because international aviation is included.

e) Categories excluded are: non-CO2 emissions in buildings and transport, part of material efficiency options, heat production and co-generation in energy supply, heavy duty vehicles, shipping and high-occupancy passenger transport, most high-cost options for buildings, wastewater treatment, emission reduction from coal mines and gas pipelines, and fluorinated gases from energy supply and transport. The underestimation of the total economic potential from these emissions is of the order of 10 to 15%.

No single technology can provide all of the mitigation potential in any sector. The economic mitigation potential, which is generally greater than the market mitigation potential, can only be achieved when adequate policies are in place and barriers removed (Table SPM.5). {4.3}

Table SPM.5 Selected examples of key sectoral mitigation technologies, policies and measures, constraints and opportunities. {Table 4.2}

Sector Key mitigation technologies and practices currently commercially available. Key mitigation technologies and practices projected to be commercialised before 2030 shown in italics. Policies, measures and instruments shown to be environmentally effective Key constraints or opportunities (Normal font = constraints; italics = opportunities
Energy supply Improved supply and distribution efficiency; fuel switching from coal to gas; nuclear power; renewable heat and power (hydropower, solar, wind, geothermal and bioenergy); combined heat and power; early applications of carbon dioxide capture and storage (CCS) (e.g. storage of removed CO2 from natural gas); CCS for gas, biomass and coal-fired electricity generating facilities; advanced nuclear power; advanced renewable energy, including tidal and wave energy, concentrating solar, and solar photovoltaics Reduction of fossil fuel subsidies; taxes or carbon charges on fossil fuels Resistance by vested interests may make them difficult to implement 
Feed-in tariffs for renewable energy technologies; renewable energy obligations; producer subsidies May be appropriate to create markets for low- emissions technologies 
Transport More fuel-efficient vehicles; hybrid vehicles; cleaner diesel vehicles; biofuels; modal shifts from road transport to rail and public transport systems; non-motorised transport (cycling, walking); land-use and transport planning; second generation biofuels; higher efficiency aircraft; advanced electric and hybrid vehicles with more powerful and reliable batteries Mandatory fuel economy; biofuel blending and CO2 standards for road transport Partial coverage of vehicle fleet may limit effectiveness 
Taxes on vehicle purchase, registration, use and motor fuels; road and parking pricing Effectiveness may drop with higher incomes 
Influence mobility needs through land-use regulations and infrastructure planning; investment in attractive public transport facilities and non-motorised forms of transport Particularly appropriate for countries that are building up their transportation systems 
Buildings Efficient lighting and daylighting; more efficient electrical appliances and heating and cooling devices; improved cook stoves, improved insulation; passive and active solar design for heating and cooling; alternative refrigeration fluids, recovery and recycling of fluorinated gases; integrated design of commercial buildings including technologies, such as intelligent meters that provide feedback and control; solar photovoltaics integrated in buildings Appliance standards and labelling Periodic revision of standards needed 
Building codes and certification Attractive for new buildings. Enforcement can be difficult  
Demand-side management programmes Need for regulations so that utilities may profit 
Public sector leadership programmes, including procurement Government purchasing can expand demand for energy-efficient products 
Incentives for energy service companies (ESCOs) Success factor: Access to third party financing  
Industry More efficient end-use electrical equipment; heat and power recovery; material recycling and substitution; control of non-CO2 gas emissions; and a wide array of process-specific technologies; advanced energy efficiency; CCS for cement, ammonia, and iron manufacture; inert electrodes for aluminium manufacture Provision of benchmark information; performance standards; subsidies; tax credits May be appropriate to stimulate technology uptake. Stability of national policy important in view of international competitiveness 
Tradable permits Predictable allocation mechanisms and stable price signals important for investments  
Voluntary agreements Success factors include: clear targets, a baseline scenario, third-party involvement in design and review and formal provisions of monitoring, close cooperation between government and industry 
Agriculture Improved crop and grazing land management to increase soil carbon storage; restoration of cultivated peaty soils and degraded lands; improved rice cultivation techniques and livestock and manure management to reduce CH4 emissions; improved nitrogen fertiliser application techniques to reduce N2O emissions; dedicated energy crops to replace fossil fuel use; improved energy efficiency; improvements of crop yields Financial incentives and regulations for improved land management; maintaining soil carbon content; efficient use of fertilisers and irrigation  May encourage synergy with sustainable development and with reducing vulnerability to climate change, thereby overcoming barriers to implementation 
Forestry/ forests  Afforestation; reforestation; forest management; reduced deforestation; harvested wood product management; use of forestry products for bioenergy to replace fossil fuel use; tree species improvement to increase biomass productivity and carbon sequestration; improved remote sensing technologies for analysis of vegetation/soil carbon sequestration potential and mapping land-use change Financial incentives (national and international) to increase forest area, to reduce deforestation and to maintain and manage forests; land-use regulation and enforcement Constraints include lack of investment capital and land tenure issues. Can help poverty alleviation 
Waste  Landfill CH4 recovery; waste incineration with energy recovery; composting of organic waste; controlled wastewater treatment; recycling and waste minimisation; biocovers and biofilters to optimise CH4 oxidation Financial incentives for improved waste and wastewater management May stimulate technology diffusion 
Renewable energy incentives or obligations Local availability of low-cost fuel 
Waste management regulations Most effectively applied at national level with enforcement strategies 

Bottom-up studies suggest that mitigation opportunities with net negative costs have the potential to reduce emissions by around 6 GtCO2-eq/yr in 2030, realising which requires dealing with implementation barriers. {4.3}

Future energy infrastructure investment decisions, expected to exceed US$20 trillion[16] between 2005 and 2030, will have long-term impacts on GHG emissions, because of the long lifetimes of energy plants and other infrastructure capital stock. The widespread diffusion of low-carbon technologies may take many decades, even if early investments in these technologies are made attractive. Initial estimates show that returning global energy-related CO2 emissions to 2005 levels by 2030 would require a large shift in investment patterns, although the net additional investment required ranges from negligible to 5 to 10%. {4.3}

A wide variety of policies and instruments are available to governments to create the incentives for mitigation action. Their applicability depends on national circumstances and sectoral context (Table SPM.5). {4.3}

They include integrating climate policies in wider development policies, regulations and standards, taxes and charges, tradable permits, financial incentives, voluntary agreements, information instruments, and research, development and demonstration (RD&D). {4.3}

An effective carbon-price signal could realise significant mitigation potential in all sectors. Modelling studies show that global carbon prices rising to US$20-80/tCO2-eq by 2030 are consistent with stabilisation at around 550ppm CO2-eq by 2100. For the same stabilisation level, induced technological change may lower these price ranges to US$5-65/tCO2-eq in 2030.[17] {4.3}

There is high agreement and much evidence that mitigation actions can result in near-term co-benefits (e.g. improved health due to reduced air pollution) that may offset a substantial fraction of mitigation costs. {4.3}

There is high agreement and medium evidence that Annex I countries’ actions may affect the global economy and global emissions, although the scale of carbon leakage remains uncertain.[18] {4.3}

Fossil fuel exporting nations (in both Annex I and non-Annex I countries) may expect, as indicated in the TAR, lower demand and prices and lower GDP growth due to mitigation policies. The extent of this spillover depends strongly on assumptions related to policy decisions and oil market conditions. {4.3}

There is also high agreement and medium evidence that changes in lifestyle, behaviour patterns and management practices can contribute to climate change mitigation across all sectors. {4.3}

Many options for reducing global GHG emissions through international cooperation exist. There is high agreement and much evidence that notable achievements of the UNFCCC and its Kyoto Protocol are the establishment of a global response to climate change, stimulation of an array of national policies, and the creation of an international carbon market and new institutional mechanisms that may provide the foundation for future mitigation efforts. Progress has also been made in addressing adaptation within the UNFCCC and additional international initiatives have been suggested. {4.5}

Greater cooperative efforts and expansion of market mechanisms will help to reduce global costs for achieving a given level of mitigation, or will improve environmental effectiveness. Efforts can include diverse elements such as emissions targets; sectoral, local, sub-national and regional actions; RD&D programmes; adopting common policies; implementing development-oriented actions; or expanding financing instruments. {4.5}

In several sectors, climate response options can be implemented to realise synergies and avoid conflicts with other dimensions of sustainable development. Decisions about macroeconomic and other non-climate policies can significantly affect emissions, adaptive capacity and vulnerability. {4.4, 5.8}

Making development more sustainable can enhance mitigative and adaptive capacities, reduce emissions and reduce vulnerability, but there may be barriers to implementation. On the other hand, it is very likely that climate change can slow the pace of progress towards sustainable development. Over the next half-century, climate change could impede achievement of the Millennium Development Goals. {5.8}

  1. ^  While this Section deals with adaptation and mitigation separately, these responses can be complementary. This theme is discussed in Section 5.
  2. ^  The concept of ‘mitigation potential’ has been developed to assess the scale of GHG reductions that could be made, relative to emission baselines, for a given level of carbon price (expressed in cost per unit of carbon dioxide equivalent emissions avoided or reduced). Mitigation potential is further differentiated in terms of ‘market mitigation potential’ and ‘economic mitigation potential’. Market mitigation potential is the mitigation potential based on private costs and private discount rates (reflecting the perspective of private consumers and companies), which might be expected to occur under forecast market conditions, including policies and measures currently in place, noting that barriers limit actual uptake. Economic mitigation potential is the mitigation potential that takes into account social costs and benefits and social discount rates (reflecting the perspective of society; social discount rates are lower than those used by private investors), assuming that market efficiency is improved by policies and measures and barriers are removed. Mitigation potential is estimated using different types of approaches. Bottom-up studies are based on assessment of mitigation options, emphasising specific technologies and regulations. They are typically sectoral studies taking the macro-economy as unchanged. Top-down studies assess the economy-wide potential of mitigation options. They use globally consistent frameworks and aggregated information about mitigation options and capture macro-economic and market feedbacks.
  3. ^  20 trillion = 20,000 billion = 20×1012
  4. ^  Studies on mitigation portfolios and macro-economic costs assessed in this report are based on top-down modelling. Most models use a global least-cost approach to mitigation portfolios, with universal emissions trading, assuming transparent markets, no transaction cost, and thus perfect implementation of mitigation measures throughout the 21st century. Costs are given for a specific point in time. Global modelled costs will increase if some regions, sectors (e.g. land use), options or gases are excluded. Global modelled costs will decrease with lower baselines, use of revenues from carbon taxes and auctioned permits, and if induced technological learning is included. These models do not consider climate benefits and generally also co-benefits of mitigation measures, or equity issues. Significant progress has been achieved in applying approaches based on induced technological change to stabilisation studies; however, conceptual issues remain. In the models that consider induced technological change, projected costs for a given stabilisation level are reduced; the reductions are greater at lower stabilisation level.
  5. ^  Further details may be found in Topic 4 of this Synthesis Report.