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Working Group II Definitions

Likelihood of an outcome or result
Virtually certain > 99% probability of occurrence
Extremely likely > 95%
Very likely > 90%
Likely > 66%
More likely than not > 50%
Very unlikely < 10%
Extremely unlikely < 5%.

Confidence in a statement
Very high confidence: At least a 9 out of 10 chance of being correct
High confidence: About an 8 out of 10 chance
Medium confidence: About a 5 out of 10 chance
Low confidence: About a 2 out of 10 chance
Very low confidence: Less than a 1 out of 10 chance

Confidence symbols in the text
*** Very high confidence
** High confidence
* Medium confidence

Key Assumptions

The Working Group II report discusses future impacts "for the range of unmitigated climate changes projected by the IPCC over this century judged to be relevant for people and the environment." Its different scenarios of future emissions of greenhouse gases "do not include additional climate initiatives, which means that no scenarios are included that explicitly assume implementation of the United Nations Framework Convention on Climate Change or the emissions targets of the Kyoto Protocol."

IPCC'S Working Group III report:
"Climate Change 2007: Mitigation of Climate Change"

On Friday, May 4, 2007 the Intergovernmental Panel on Climate Change (IPCC) released a Summary for Policy Makers from its Working Group III report, "Climate Change 2007: Mitigation of Climate Change," in Bangkok, Thailand.

Key passages from this new Working Group III report are posted below. The solutions-oriented report outlines the actions, policies and incentives that governments and industries can implement in coming decades to address the causes of global warming. The full text summary reports are available on the IPCC website: http://www.ipcc.ch.

A teleconference for journalists, featuring IPCC Working Group III co-chairs Dr. Bert Metz and Dr. Ogunlade Davidson and other lead authors from the U.S., was held on May 4, 2007.

To listen to a recording of the teleconference, click here.

This website also provides:

Key Passages from Working Group III:

Emission Trends, Short Term Mitigation, Long Term Mitigation, Policies

This new report on solutions to global warming provides in-depth analysis of the costs and benefits of different approaches to mitigating global warming by sector, in the short term--between now and 2030--and the long term--looking beyond 2030. The report outline how choices made now by governments and industries around the world will affect future energy security, air quality, public health, employment and the global trade balance. Key passages include:

Greenhouse gas emission trends

"Global greenhouse gas (GHG) emissions have grown since pre-industrial times, with an increase of 70% between 1970 and 2004 (high agreement, much evidence)."

"The largest growth in global GHG emissions between 1970 and 2004 has come from the energy supply sector (an increase of 145%). The growth in direct emissions in this period from transport was 120%, industry 65% and land use, land use change, and forestry (LULUCF) 40%. Between 1970 and 1990 direct emissions from agriculture grew by 27% and from buildings by 26%, and the latter remained at approximately at 1990 levels thereafter. However, the buildings sector has a high level of electricity use and hence the total of direct and indirect emissions in this sector is much higher (75%) than direct emissions."

"The effect on global emissions of the decrease in global energy intensity (-33%) during 1970 to 2004 has been smaller than the combined effect of global income growth (77 %) and global population growth (69%); both drivers of increasing energy-related CO2 emissions (Figure SPM.2). The long-term trend of a declining carbon intensity of energy supply reversed after 2000. Differences in terms of per capita income, per capita emissions, and energy intensity among countries remain significant. (Figure SPM.3). In 2004 UNFCCC Annex I countries held a 20% share in world population, produced 57% of world Gross Domestic Product based on Purchasing Power Parity (GDPppp), and accounted for 46% of global GHG emissions (Figure SPM.3a)."

"A range of policies, including those on climate change, energy security, and sustainable development, have been effective in reducing GHG emissions in different sectors and many countries. The scale of such measures, however, has not yet been large enough to counteract the global growth in emissions."

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Mitigation in the short and medium term (until 2030)

"With current climate change mitigation policies and related sustainable development practices, global GHG emissions will continue to grow over the next few decades (high agreement, much evidence)."

"Both bottom-up and top-down studies indicate that there is 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 (high agreement, much evidence)."

Sector Key mitigation technologies and practices currently commercially available. Key mitigation technologies and practices projected to be commercialized before 2030.
Energy Supply
[4.3, 4.4]
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 CCS (e.g. storage of removed CO2 from natural gas) Carbon Capture and Storage (CCS) for gas, biomass and coal-fired electricity generating facilities; advanced nuclear power; advanced renewable energy, including tidal and waves energy, concentrating solar, and solar PV.
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
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 recycle of fluorinated gases Integrated design of commercial buildings including technologies, such as intelligent meters that provide feedback and control; solar PV integrated in buildings
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
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 fertilizer application techniques to reduce N2O emissions; dedicated energy crops to replace fossil fuel use; improved energy efficiency Improvements of crops yields
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
Landfill methane recovery; waste incineration with energy recovery; composting of organic waste; controlled waste water treatment; recycling and waste minimization Biocovers and biofilters to optimize CH4 oxidation

"In 2030 macro-economic costs for multi-gas mitigation, consistent with emissions trajectories towards stabilization between 445 and 710 ppm CO2-eq, are estimated at between a 3% decrease of global GDP and a small increase, compared to the baseline (see Table SPM.4). However, regional costs may differ significantly from global averages (high agreement, medium evidence)"

"The majority of studies conclude that reduction of GDP relative to the GDP baseline increases with the stringency of the stabilization target."

Table SPM.4: Estimated global macro-economic costs in 2030 for least-cost trajectories towards different long-term stabilization levels

Stabilization levels (ppm CO2-eq) Median GDP reduction (%) Range of GDP reduction (%) Reduction of average annual GDP growth rates (percentage points)
590-710 0.2 -0.6 — 1.2 < 0.06
535-590 0.6 0.2 — 2.5 < 0.1
445-535 Not available < 3 < 0.12

"Depending on the existing tax system and spending of the revenues, modelling studies indicate that costs may be substantially lower under the assumption that revenues from carbon taxes or auctioned permits under an emission trading system are used to promote low-carbon technologies or reform of existing taxes."

"Studies that assume the possibility that climate change policy induces enhanced technological change also give lower costs. However, this may require higher upfront investment in order to achieve costs reductions thereafter."

"Although most models show GDP losses, some show GDP gains because they assume that baselines are non-optimal and mitigation policies improve market efficiencies, or they assume that more technological change may be induced by mitigation policies."

"Examples of market inefficiencies include unemployed resources, distortionary taxes and/or subsidies."

"A multi-gas approach and inclusion of carbon sinks generally reduces costs substantially compared to CO2 emission abatement only."

"Lifestyle changes can reduce GHG emissions. Changes in lifestyles and consumption patterns that emphasize resource conservation can contribute to developing a low-carbon economy that is both equitable and sustainable."

"Changes in occupant behaviour, cultural patterns and consumer choice and use of technologies can result in considerable reduction in CO2 emissions related to energy use in buildings."

"While studies use different methodologies, in all analyzed world regions near-term health co-benefits from reduced air pollution as a result of actions to reduce GHG emissions can be substantial and may offset a substantial fraction of mitigation costs (high agreement, much evidence)."

"New energy infrastructure investments in developing countries, upgrades of energy infrastructure in industrialized countries, and policies that promote energy security, can, in many cases, create opportunities to achieve GHG emission reductions compared to baseline scenarios. Additional co-benefits are country-specific but often include air pollution abatement, balance of trade improvement, provision of modern energy services to rural areas and employment (high agreement, much evidence)."

"Future energy infrastructure investment decisions, expected to total over 20 trillion US$ between now and 2030, will have long term impacts on GHG emissions, because of the long life-times 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 the pattern of investment, although the net additional investment required ranges from negligible to 5-10%."

"It is often more cost-effective to invest in end-use energy efficiency improvement than in increasing energy supply to satisfy demand for energy services. Efficiency improvement has a positive effect on energy security, local and regional air pollution abatement, and employment."

"Renewable energy generally has a positive effect on energy security, employment and on air quality. Given costs relative to other supply options, renewable electricity, which accounted for 18% of the electricity supply in 2005, can have a 30-35% share of the total electricity supply in 2030 at carbon prices up to 50 US$/tCO2-eq."

"Given costs relative to other supply options, nuclear power, which accounted for 16% of the electricity supply in 2005, can have an 18% share of the total electricity supply in 2030 at carbon prices up to 50 US$/tCO2-eq, but safety, weapons proliferation and waste remain as constraints."

"CCS in underground geological formations is a new technology with the potential to make an important contribution to mitigation by 2030. Technical, economic and regulatory developments will affect the actual contribution."

"Improved vehicle efficiency measures, leading to fuel savings, in many cases have net benefits (at least for light-duty vehicles), but the market potential is much lower than the economic potential due to the influence of other consumer considerations, such as performance and size. There is not enough information to assess the mitigation potential for heavy-duty vehicles. Market forces alone, including rising fuel costs, are therefore not expected to lead to significant emission reductions [5.3, 5.4]."

"Energy efficiency options for new and existing buildings could considerably reduce CO2 emissions with net economic benefit. Many barriers exist against tapping this potential, but there are also large co-benefits (high agreement, much evidence)."

"By 2030, about 30% of the projected GHG emissions in the building sector can be avoided with net economic benefit."

"Agricultural practices collectively can make a significant contribution at low cost to increasing soil carbon sinks, to GHG emission reductions, and by contributing biomass feedstocks for energy use (medium agreement, medium evidence)."

"A large proportion of the mitigation potential of agriculture (excluding bioenergy) arises from soil carbon sequestration, which has strong synergies with sustainable agriculture and generally reduces vulnerability to climate change."

"Forest-related mitigation activities can considerably reduce emissions from sources and increase CO2 removals by sinks at low costs, and can be designed to create synergies with adaptation and sustainable development (high agreement, much evidence)."

"About 65% of the total mitigation potential (up to 100 US$/tCO2-eq) is located in the tropics and about 50% of the total could be achieved by reducing emissions from deforestation."

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Mitigation in the long term (after 2030)

"In order to stabilize the concentration of GHGs in the atmosphere, emissions would need to peak and decline thereafter. The lower the stabilization level, the more quickly this peak and decline would need to occur. Mitigation efforts over the next two to three decades will have a large impact on opportunities to achieve lower stabilization levels (see Table SPM.5, and Figure SPM. 8) (high agreement, much evidence)."

"The range of stabilization levels assessed can be achieved by deployment of a portfolio of technologies that are currently available and those that are expected to be commercialised in coming decades. This assumes that appropriate and effective incentives are in place for development, acquisition, deployment and diffusion of technologies and for addressing related barriers (high agreement, much evidence)."

"Energy efficiency plays a key role across many scenarios for most regions and timescales."

"For lower stabilization levels, scenarios put more emphasis on the use of low-carbon energy sources, such as renewable energy and nuclear power, and the use of CO2 capture and storage (CCS). In these scenarios improvements of carbon intensity of energy supply and the whole economy need to be much faster than in the past."

"Including non-CO2 and CO2 land-use and forestry mitigation options provides greater flexibility and cost-effectiveness for achieving stabilization. Modern bioenergy could contribute substantially to the share of renewable energy in the mitigation portfolio. "

"Investments in and world-wide deployment of low-GHG emission technologies as well as technology improvements through public and private Research, Development & Demonstration (RD&D) would be required for achieving stabilization targets as well as cost reduction. The lower the stabilization levels, especially those of 550 ppm CO2-eq or lower, the greater the need for more efficient RD&D efforts and investment in new technologies during the next few decades."

"In 2050 global average macro-economic costs for multi-gas mitigation towards stabilization between 710 and 445 ppm CO2-eq, are between a 1% gain to a 5.5% decrease of global GDP (see Table SPM.6). For specific countries and sectors, costs vary considerably from the global average. (See Box SPM.3 for the methodologies and assumptions and paragraph 5 for explanation of negative costs) (high agreement, medium evidence)."

Table SPM.6: Estimated global macro-economic costs in 2050 relative to the baseline for least-cost trajectories towards different long-term stabilization targets [3.3, 13.3]

Stabilization levels (ppm CO2-eq) Median GDP reduction (%) Range of GDP reduction (%) Reduction of average annual GDP growth rates (percentage points)
590-710 0.5 -1 — 2 < 0.05
535-590 1.3 slightly negative — 4 < 0.1
445-535 Not available < 5.5 < 0.12

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Policies, measures and instruments to mitigate climate change

"Policies that provide a real or implicit price of carbon could create incentives for producers and consumers to significantly invest in low-GHG products, technologies and processes. Such policies could include economic instruments, government funding and regulation (high agreement, much evidence)."

"An effective carbon-price signal could realize significant mitigation potential in all sectors."

"Modelling studies (see Box SPM.3) show carbon prices rising to 20 to 80 US$/tCO2-eq by 2030 and 30 to 155 US$/tCO2-eq by 2050 are consistent with stabilization at around 550 ppm CO2-eq by 2100. For the same stabilization level, studies since TAR that take into account induced technological change lower these price ranges to 5 to 65 US$/tCO2eq in 2030 and 15 to 130 US$/tCO2-eq in 2050 [3.3, 11.4, 11.5]."

"Most top-down, as well as some 2050 bottom-up assessments, suggest that real or implicit carbon prices of 20 to 50 US$/tCO2-eq, sustained or increased over decades, could lead to a power generation sector with low-GHG emissions by 2050 and make many mitigation options in the end-use sectors economically attractive. [4.4,11.6]"

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Table SPM.7: Selected sectoral policies, measures and instruments that have shown to be environmentally effective in the respective sector in at least a number of national cases.

Sector Policies, measures and instruments shown to be environmentally effective Key constraints or opportunities
Energy supply [4.5] Reduction of fossil fuel subsidies Resistance by vested interests may make them difficult to implement
Taxes or carbon charges on fossil fuels
Feed-in tariffs for renewable energy technologies May be appropriate to create markets for low emissions technologies
Renewable energy obligations
Producer subsidies
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 Particularly appropriate for countries that are building up their transportation systems
Investment in attractive public transport facilities and non-motorised forms of transport
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
Sector Policies, measures and instruments shown to be environmentally effective Key constraints or opportunities
Provision of benchmark information May be appropriate to stimulate technology uptake. Stability of national policy important in view of international competitiveness
Performance standards
Subsidies, tax credits
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.
[8.6, 8.7, 8.8]
Financial incentives and regulations for improved land management, maintaining soil carbon content, efficient use of fertilizers and irrigation May encourage synergy with sustainable development and with reducing vulnerability to climate change, thereby overcoming barriers to implementation
Financial incentives (national and international) to increase forest area, to reduce deforestation, and to maintain and manage forests Constraints include lack of investment capital and land tenure issues. Can help poverty alleviation.
Land use regulation and enforcement
Waste management
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

"Government support through financial contributions, tax credits, standard setting and market creation is important for effective technology development, innovation and deployment. Transfer of technology to developing countries depends on enabling conditions and financing (high agreement, much evidence)."

"Public benefits of RD&D investments are bigger than the benefits captured by the private sector, justifying government support of RD&D."

"Government funding in real absolute terms for most energy research programmes has been flat or declining for nearly two decades (even after the UNFCCC came into force) and is now about half of the 1980 level."

"Governments have a crucial supportive role in providing appropriate enabling environment, such as, institutional, policy, legal and regulatory frameworks, to sustain investment flows and for effective technology transfer — without which it may be difficult to achieve emission reductions at a significant scale. Mobilizing financing of incremental costs of low-carbon technologies is important. International technology agreements could strengthen the knowledge infrastructure."

"The literature identifies many options for achieving reductions of global GHG emissions at the international level through cooperation. It also suggests that successful agreements are environmentally effective, cost-effective, incorporate distributional considerations and equity, and are institutionally feasible (high agreement, much evidence). "

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Outline of the IPCC's Fourth Assessment Report (AR4)

North America Chapter of the IPCC's WGII Technical Report: "Climate Change 2007: Impacts, Adaptation and Vulnerability"

AR4 Working Group II report: "Climate Change 2007: Impacts, Adaptation and Vulnerability"

AR4 Working Group I report: "Climate Change 2007: The Physical Science Basis"

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