Coordinating Lead Authors:

H-Holger Rogner (Germany), Dadi Zhou (China) [SRC:1],

Lead Authors:

Rick Bradley (USA) [PoC], , Philippe Crabbé (Canada), Ottmar Edenhofer (Germany) [SRC:1], Bill Hare (Australia), Lambert Kuijpers (The Netherlands), Mitsutsune Yamaguchi (Japan),

Contributing Authors:

Nicolas Lefevre (France/USA), Jos Olivier (The Netherlands) [SRC:2], Hongwei Yang (China),

Review Editors:

Hoesung Lee (Republic of Korea), Richard Odingo (Kenya),

This chapter should be cited as:

Rogner, H.-H., D. Zhou, R. Bradley. P. Crabbé, O. Edenhofer, B.Hare (Australia), L. Kuijpers, M. Yamaguchi, 2007: Introduction. In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

1.2.1 Article 2 of the Convention

Article 2 of the UNFCCC specifies the ultimate objective of the Convention and states:

‘The ultimate objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner’ ( UN, 1992 [NPR] ).

The criterion that relates to enabling economic development to proceed in a sustainable manner is a double-edged sword. Projected anthropogenic climate change appears likely to adversely affect sustainable development, with adverse effects tending to increase with higher levels of climate change and GHG concentrations ( IPCC, 2007b [NPR, 2007] , SPM and Chapter 19). Conversely, costly mitigation measures could have adverse effects on economic development. This dilemma facing policymakers results in (a varying degree of) tension that is manifested in the debate over the scale of the interventions and the balance to be adopted between climate policy (mitigation and adaptation) and economic development.

The assessment of impacts, vulnerability and adaptation potentials is likely to be important for determinating the levels and rates of climate change which would result in ecosystems, food production or economic development being threatened to a level sufficient to be defined as dangerous. Vulnerabilities to anthropogenic climate change are strongly regionally differentiated, with often those in the weakest economic and political position being the most susceptible to damages ( IPCC, 2007b [NPR, 2007] , Chapter 19, Tables 19.1 and 19.3.3).

Limits to climate change or other changes to the climate system that are deemed necessary to prevent dangerous anthropogenic interference with the climate system can be defined in terms of various – and often quite different – criteria, such as concentration stabilization at a certain level, global mean temperature or sea level rise or levels of ocean acidification. Whichever limit is chosen, its implementation would require the development of consistent emission pathways and levels of mitigation ( Chapter 3 ).

1.2.2 What is dangerous interference with the climate system?

Defining what is dangerous interference with the climate system is a complex task that can only be partially supported by science, as it inherently involves normative judgements. There are different approaches to defining danger, and an interpretation of Article 2 is likely to rely on scientific, ethical, cultural, political and/or legal judgements. As such, the agreement(s) reached among the Parties in terms of what may constitute unacceptable impacts on the climate system, food production, ecosystems or sustainable economic development will represent a synthesis of these different perspectives.

Over the past two decades several expert groups have sought to define levels of climate change that could be tolerable or intolerable, or which could be characterized by different levels of risk. In the late 1980 s, the World Meteorological Organization (WMO)/International Council of Scientific Unions (ICSU)/UN Environment Programme (UNEP) Advisory Group on Greenhouse Gases (AGGG) identified two main temperature indicators or thresholds with different levels of risk ( Rijsberman and Swart, 1990 [NPR, ARC] ). Based on the available knowledge at the time a 2ºC increase was determined to be ‘an upper limit beyond which the risks of grave damage to ecosystems, and of non-linear responses, are expected to increase rapidly’. This early work also identified the rate of change to be of importance to determining the level of risk, a conclusion that has subsequently been confirmed qualitatively ( IPCC, 2007b [NPR, 2007] , Chapters 4 and 19). More recently, others in the scientific community have reached conclusions that point in a similar direction ‘that global warming of more than 1°C, relative to 2000, will constitute “dangerous” climate change as judged from likely effects on sea level and extermination of species’ ( Hansen et al., 2006 [NPR] ). Probabilistic assessments have also been made that demonstrate how scientific uncertainties, different normative judgments on acceptable risks to different systems ( Mastrandrea and Schneider, 2004 [PoC, JoC, ARC] ) and/or interference with the climate system ( Harvey, 2007 [2007] ) affect the levels of change or interference set as goals for policy ( IPCC, 2007b [NPR, 2007] , Chapter 19). From an economic perspective, the Stern Review ( Stern, 2006 [NPR] ) found that in order to minimise the most harmful consequences of climate change, concentrations would need to be stabilized below 550 ppm CO₂-eq. The Review further argues that any delay in reducing emissions would be ‘would be costly and dangerous’. This latter conclusion is at variance with the conclusions drawn from earlier economic analyses which support a slow ‘ramp up’ of climate policy action ( Nordhaus, 2006 [NPR] ) and, it has been argued, is a consequence of the approach taken by the Stern Review to intergenerational equity ( Dasgupta, 2006 [NPR] ).

The IPCC Third Assessment Report (TAR) identified five broad categories of reasons for concern that are relevant to Article 2: (1) Risks to unique and threatened systems, (2) risks from extreme climatic events, (3) regional distribution of impacts, (4) aggregate impacts and (5) risks from large-scale discontinuities. The Fourth Assessment Report (AR4) focuses on Key Vulnerabilities relevant to Article 2, which are broadly categorized into biological systems, social systems, geophysical systems, extreme events and regional systems ( IPCC, 2007b [NPR, 2007] , Chapter 19). The implications of different interpretations of dangerous anthropogenic interference for future emission pathways are reviewed in IPCC 2007b [NPR, 2007] ), Chapter 9 and also in Chapter 3 of this report. The literature confirms that climate policy can substantially reduce the risk of crossing thresholds deemed dangerous ( IPCC, 2007b [NPR, 2007] , SPM and Chapter 19; Chapter 3 , Section 3.5.2 of this report).

While the works cited above are principally scientific (expert-led) assessments, there is also an example of governments seeking to define acceptable levels of climate change based on interpretations of scientific findings. In 2005, the EU Council (25 Heads of Government of the European Union) agreed that – with a view to achieving the ultimate objective of the Convention – the global annual mean surface temperature increase should not exceed 2ºC above pre-industrial levels ( CEU, 2005 [NPR] ).

1.2.3 Issues related to the implementation of Article 2

Decisions made in relation to Article 2 will determine the level of climate change that is set as the goal for policy and have fundamental implications for emission reduction pathways, the feasibility, timing and scale of adaptation required and the magnitude of unavoidable losses. The emission pathways which correspond to different GHG or radiative forcing stabilization levels and consequential global warming are reviewed in Chapter 3 (see Tables 3.9 and 3.10 ). The potential consequences of two hypothetical limits can provide an indication of the differing scales of mitigation action that depend on Article 2 decisions: A 2ºC above pre-industrial limit on global warming would implies that emissions peak within the next decade and be reduced to less than 50% of the current level by 2050 ^[3] ; a 4ºC limit would imply that emissions may not have to peak until well after the middle of the century and could still be well above 2000 levels in 2100 . In relation to the first hypothetical limt, the latter would have higher levels of adaptation costs and unavoidable losses, but carry lower mitigation costs.

Issues related to the mitigation, adaptation and sustainable development aspects of the implementation of Article 2 thus include, among others, the linkages between sustainable development and the adverse effects climate change, the need for equity and cooperation and the recognition of common but differentiated responsibilities and respective capabilities as well as the precautionary principle (see Section 1.4.1 for more detail on relevant UNFCCC Articles that frame these issues). In this context, risk management issues which take into account several key aspects of the climate change problem, such as inertia, irreversibility, the risk of abrupt or catastrophic changes and uncertainty, are introduced in this section and discussed in more detail in Chapters 2 , 3 and 11 .

1.3.1 Review of the last three decades

Since pre-industrial times, increasing emissions of GHGs due to human activities have led to a marked increase in atmospheric concentrations of the long-lived GHG gases carbon dioxide (CO₂), CH₄, and nitrous oxide (N₂O), perfluorocarbons PFCs, hydrofluorocarbons (HFCs) and sulphur hexafluoride (SF₆) and ozone-depleting substances (ODS; chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons) and the human-induced radiative forcing of the Earth’s climate is largely due to the increases in these concentrations. The predominant sources of the increase in GHGs are from the combustion of fossil fuels. Atmospheric CO₂ concentrations have increased by almost 100 ppm in comparison to its preindustrial levels, reaching 379 ppm in 2005, with mean annual growth rates in the 2000 – 2005 period that were higher than those in the 1990 s.

The direct effect of all the long-lived GHGs is substantial, with the total CO₂ equivalent concentration of these gases currently being estimated to be around 455 ppm CO₂-eq ^[5] (range: 433–477 ppm CO₂-eq). The effects of aerosol and land-use changes reduce radiative forcing so that the net forcing of human activities is in the range of 311 to 435 ppm CO₂-eq, with a central estimate of about 375 ppm CO₂-eq.

A variety of sources exist for determining global and regional GHG and other climate forcing agent trends. Each source has its strengths and weaknesses and uncertainties. The EDGAR database ( Olivier et al., 2005 [SRC] , 2006 ) contains global GHG emission trends categorized by broad sectors for the period 1970 – 2004, and Marland et al. 2006 [NPR] ) report CO₂ emissions on a global basis. Both databases show a similar temporal evolution of emissions. Since 1970, the global warming potential (GWP)-weighted emissions of GHGs (not including ODS which are controlled under the Montreal Protocol), have increased by approximately 70%, (24% since 1990 ), with CO₂ being the largest source, having grown by approximately 80% (28% since 1990 ) to represent 77% of total anthropogenic emissions in 2004 (74% in 1990 ) ( Figure 1.1 ). Radiative forcing as a result of increases in atmospheric CO₂ concentrations caused by human activities since the preindustrial era predominates over all other radiative forcing agents ( IPCC, 2007a [NPR, 2007] , SPM). Total CH₄ emissions have risen by about 40% from 1970 (11% from 1990 ), and on a sectoral basis there has been an 84% (12% from 1990 ) increase from combustion and the use of fossil fuels, while agricultural emissions have remained roughly stable due to compensating falls and increases in rice and livestock production, respectively. N₂O emissions have grown by 50% since 1970 (11% since 1990 ), mainly due to the increased use of fertilizer and the aggregate growth of agriculture. Industrial process emissions of N₂O have fallen during this period.

Figure 1.1a Global anthropogenic greenhouse gas trends, 1970 – 2004 .

One-hundred year global warming potentials (GWPs) from the Intergovernmental Panel on Climate Change ( IPCC) 1996 [NPR] (SAR) were used to convert emissions to CO₂ equivalents (see the UNFCCC reporting guidelines). Gases are those reported under UNFCCC reporting guidelines. The uncertainty in the graph is quite large for CH₄ and N₂O (of the order of 30–50%) and even larger for CO₂ from agriculture and forestry.

Notes:

1. Other N₂O includes industrial processes, deforestation/savannah burning, waste water and waste incineration.

2. Other is CH₄ from industrial processes and savannah burning.

3. Including emissions from bio energy production and use.

4. CO₂ emissions from decay (decomposition) of above ground biomass that remains after logging and deforestation and CO₂ from peat fires and decay of drained peat soils.

5. As well as traditional biomass use at 10% of total, assuming 90% is from sustainable biomass production. Corrected for the 10% of carbon in biomass that is assumed to remain as charcoal after combustion.

6. For large-scale forest and scrubland biomass burning averaged data for 1997 - 2002 based on Global Fire Emissions Data base satellite data.

7. Cement production and natural gas flaring.

8. Fossil fuel use includes emissions from feedstocks.

Source: Adapted from Olivier et al., 2005 [SRC] ; 2006; Hooijer et al., 2006 [NPR]

Figure 1.1b Global anthropogenic greenhouse gas emissions in 2004 .

Source: Adapted from Olivier et al., 2005 [SRC] , 2006

The use and emissions of all fluorinated gases (including those controlled under the Montreal Protocol) decreased substantially during 1990 – 2004 . The emissions, concentrations and radiative forcing of one type of fluorinated gas, the HFCs, grew rapidly during this period as these replaced ODS; in 2004, CFCs were estimated to constitute about 1.1% of the total GHG emissions (100-year GWP) basis. Current annual emissions of all fluorinated gases are estimated at 2.5 GtCO₂-eq, with HFCs at 0.4 GtCO₂-eq. The stocks of these gases are much larger and currently represent about 21 GtCO₂-eq.

The largest growth in CO₂ emissions has come from the power generation and road transport sectors, with the industry, households and the service sector ^[6] remaining at approximately the same levels between 1970 and 2004 ( Figure 1.2 ). By 2004, CO₂ emissions from power generation represented over 27% of the total anthropogenic CO₂ emissions and the power sector was by far its most important source. Following the sectoral breakdown adopted in this report (Chapters 4 – 10 ), in 2004 about 26% of GHG emissions were derived from energy supply (electricity and heat generation), about 19% from industry, 14% from agriculture ^[7] , 17% from land use and land-use change ^[8] , 13% from transport, 8% from the residential, commercial and service sectors and 3% from waste (see Figure 1.3 ). These values should be regarded as indicative only as some uncertainty remains, particularly with regards to CH₄ and N₂O emissions, for which the error margin is estimated to be in the order of 30–50%, and CO₂ emissions from agriculture, which have an even larger error margin.

Figure 1.2: Sources of global CO₂ emissions, 1970 – 2004 (only direct emissions by sector).

¹⁾ Including fuelwood at 10% net contribution. For large-scale biomass burning, averaged data for 1997 – 2002 are based on the Global Fire Emissions Database satellite data ( (van der Werf et al., 2003 ) ). Including decomposition and peat fires ( Hooijer et al., 2006 [NPR] ). Excluding fossil fuel fires.

²⁾ Other domestic surface transport, non-energetic use of fuels, cement production and venting/flaring of gas from oil production.

³⁾ Including aviation and marine transport.

Source: Adapted from Olivier et al., 2005 [SRC] ; 2006 ).

Figure 1.3a: GHG emissions by sector in 1990 and 2004 .

Source: Adapted from Olivier et al., 2005 [SRC] , 2006 .

Figure 1.3b: GHG emissions by sector in 2004 .

Source: Adapted from Olivier et al., 2005 [SRC] ; 2006 .

Since 1970, GHG emissions from the energy supply sector have grown by over 145%, while those from the transport sector have grown by over 120%; as such, these two sectors show the largest growth in GHG emissions. The industry sector’s emissions have grown by close to 65%, LULUCF (land use, land-use change and forestry) by 40% while the agriculture sector (27%) and residential/commercial sector (26%) have experienced the slowest growth between 1970 and 2004 .

The land-use change and forestry sector plays a significant role in the overall carbon balance of the atmosphere. However, data in this area are more uncertain than those for other sectors. The Edgar database indicates that, in 2004, the share of CO₂ emissions from deforestation and the loss of carbon from soil decay after logging constituted approximately 7–16% of the total GHG emissions (not including ODS) and between 11 and 28% of fossil CO₂ emissions. Estimates vary considerably. There are large emissions from deforestation and other land-use change activities in the tropics; these have been estimated in IPCC 2007a [NPR, 2007] ) for the 1990 s to have been 5.9 GtCO₂-eq, with a large uncertainty range of 1.8–9.9 GtCO₂-eq ( Denman et al., 2007 [NPR, ARC, 2007] ). This is about 25% (range: 8–42%) of all fossil fuel and cement emissions during the 1990 s. The underlying factors accounting for the large range in the estimates of tropical deforestation and land-use changes emissions are complex and not fully resolved at this time ( Ramankutty et al., 2006 [NPR, MoS] ). For the Annex I Parties that have reported LULUCF sector data to the UNFCCC (including agricultural soils and forests) since 1990, the aggregate net sink reported for emissions and removals over the period up to 2004 average out to approximately 1.3 GtCO₂-eq (range: –1.5 to –0.9 GtCO₂-eq) ^[9] .

On a geographic basis, there are important differences between regions. North America, Asia and the Middle East have driven the rise in emissions since 1972 . The former countries of the Soviet Union have shown significant reductions in CO₂ emissions since 1990, reaching a level slightly lower than that in 1972 . Developed countries (UNFCCC Annex I countries) hold a 20% share in the world population but account for 46.4% of global GHG emissions. In contrast, the 80% of the world population living in developing countries (non-Annex I countries) account for 53.6% of GHG emissions (see Figure 1.4 a). Based on the metric of GHG emission per unit of economic output (GHG/GDP_ppp) ^[10] , Annex I countries generally display lower GHG intensities per unit of economic production process than non-Annex I countries (see Figure 1.4 b).

Figure 1.4a: Distribution of regional per capita GHG emissions (all Kyoto gases including those from land-use) over the population of different country groupings in 2004. The percentages in the bars indicate a region’s share in global GHG emissions.

Source: Adapted from Bolin and Khesgi, 2001) using IEA and EDGAR 3.2 database information (Olivier et al., 2005, 2006).

Figure 1.4b: Distribution of regional GHG emissions (all Kyoto gases including those from land-use) per USD of GDP_ppp over the GDP of different country groupings in 2004. The percentages in the bars indicate a region’s share in global GHG emissions.

Source: IEA and EDGAR 3.2 database information (Olivier et al., 2005, 2006).

Note: Countries are grouped according to the classification of the UNFCCC and its Kyoto Protocol; this means that countries that have joined the European Union since then are still listed under EIT Annex I. A full set of data for all countries for 2004 was not available. The countries in each of the regional groupings include:

• EIT Annex I: Belarus, Bulgaria, Croatia, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, Russian Federation, Slovakia, Slovenia, Ukraine
• Europe Annex II & M&T: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Liechtenstein, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom; Monaco and Turkey
• JANZ: Japan, Australia, New Zealand.
• Middle East: Bahrain, Islamic Republic of Iran, Israel, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia, Syria, United Arab Emirates, Yemen
• Latin America & the Caribbean: Antigua & Barbuda, Argentina, Bahamas, Barbados, Belize, Bolivia, Brazil, Chile, Colombia, Costa Rica, Cuba, Dominica, Dominican Republic, Ecuador, El Salvador, Grenada, Guatemala, Guyana, Haiti, Honduras, Jamaica, Mexico, Nicaragua, Panama, Paraguay, Peru, Saint Lucia, St. Kitts-Nevis-Anguilla, St. Vincent-Grenadines, Suriname, Trinidad and Tobago, Uruguay, Venezuela
• Non-Annex I East Asia: Cambodia, China, Korea (DPR), Laos (PDR), Mongolia, Republic of Korea, Viet Nam.
• South Asia: Afghanistan, Bangladesh, Bhutan, Comoros, Cook Islands, Fiji, India, Indonesia, Kiribati, Malaysia, Maldives, Marshall Islands, Micronesia, (Federated States of), Myanmar, Nauru, Niue, Nepal, Pakistan, Palau, Papua New Guinea, Philippine, Samoa, Singapore, Solomon Islands, Sri Lanka, Thailand, Timor-Leste, Tonga, Tuvalu, Vanuatu
• North America: Canada, United States of America.
• Other non-Annex I: Albania, Armenia, Azerbaijan, Bosnia Herzegovina, Cyprus, Georgia, Kazakhstan, Kyrgyzstan, Malta, Moldova, San Marino, Serbia, Tajikistan, Turkmenistan, Uzbekistan, Republic of Macedonia
• Africa: Algeria, Angola, Benin, Botswana, Burkina Faso, Burundi, Cameroon, Cape Verde, Central African Republic, Chad, Congo, Democratic Republic of Congo, Côte d’Ivoire, Djibouti, Egypt, Equatorial Guinea, Eritrea, Ethiopia, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Lesotho, Liberia, Libya, Madagascar, Malawi, Mali, Mauritania, Mauritius, Morocco, Mozambique, Namibia, Niger, Nigeria, Rwanda, Sao Tome and Principe, Senegal, Seychelles, Sierra Leone, South Africa, Sudan, Swaziland, Togo, Tunisia, Uganda, United Republic of Tanzania, Zambia, Zimbabwe

The promotion of energy efficiency improvements and fuel switching are among the most frequently applied policy measures that result in mitigation of GHG emissions. Although they may not necessarily be targeted at GHG emission mitigation, such policy measures do have a strong impact in lowering the emission level from where it would be otherwise.

According to an analysis of GHG mitigation activities in selected developing countries by Chandler et al. 2002 [NPR, SRC] ), the substitution of gasoline-fuelled cars with ethanol-fuelled cars and that of conventional CHP (combined heat and power; also cogeneration) plants with sugar-cane bagasse CHP plants in Brazil resulted in an estimated carbon emission abatement of 23.5 MtCO₂ in 2000 (actual emissions in 2000 : 334 MtCO₂). According to the same study, economic and energy reforms in China curbed the use of low-grade coal, resulting in avoided emissions of some 366 MtCO₂ (actual emissions: 3,100 MtCO₂). In India, energy policy initiatives including demand-side efficiency improvements are estimated to have reduced emissions by 66 MtCO₂ (compared with the actual emission level of 1,060 MtCO₂). In Mexico, the switch to natural gas, the promotion of efficiency improvements and lower deforestation are estimated to have resulted in 37 MtCO₂ of emission reductions, compared with actual emissions of 685 MtCO₂.

For the EU-25 countries, the European Environment Agency ( EEA, 2006 [NPR] ) provides a rough estimate of the avoided CO₂ emissions from public electricity and heat generation due to efficiency improvements and fuel switching. If the efficiency and fuel mix had remained at their 1990 values, emissions in 2003 would have been some 34% above actual emissions, however linking these reductions to specific policies was found to be difficult. For the UK and Germany about 60% of the reductions from 1990 to 2000 were found to be due to factors other than the effects of climate-related policies ( Eichhammer et al., 2001 [NPR, ARC] , 2002 ).

Since 2000, however, many more policies have been put into place, including those falling under the European Climate Change Programme (ECCP), and significant progress has been made, including the establishment of the EU Emissions Trading Scheme (EU ETS) ( CEC, 2006 [NPR] ). A review of the effectiveness of the first stage of the ECCP reported that about one third of the potential reductions had been fully implemented by mid 2006 ^[11] . Overall EU-25 emissions in 2004 were 0.9% lower than in the base year, and the European Commission (EC) assessed the EC Kyoto target (8% reduction relative to the base year) to be within reach under the conditions that (1) all additional measures currently under discussion are put into force in time, (2) Kyoto mechanisms are used to the full extent planned and (3) removals from Articles 3.3 and 3.4 activities (carbon sinks) contribute to the extent projected ( CEC, 2006 [NPR] ). Overall this shows that climate policies can be effective, but that they are difficult to fully implement and require continual improvement in order to achieve the desired objectives.

1.3.1.2 Intensities

The Kaya identity ( Kaya, 1990 [NPR] ) is a decomposition that expresses the level of energy related CO₂ emissions as the product of four indicators: (1) carbon intensity (CO₂ emissions per unit of total primary energy supply (TPES)), (2) energy intensity (TPES per unit of GDP), (3) gross domestic product per capita (GDP/cap) and (4) population. The global average growth rate of CO₂ emissions between 1970 and 2004 of 1.9% per year is the result of the following annual growth rates: population 1.6%, GDP/cap ^[12] 1.8%, energy-intensity of –1.2% and carbon-intensity –0.2% ( Figure 1.5 ).

Figure 1.5: Intensities of energy use and CO₂ emissions, 1970 – 2004 .

Data Source: IEA data

A decomposition analysis according to the refined Laspeyeres index method ( Sun, 1998 [MoS] ; Sun and Ang, 2000 [MoS] ) is shown in Figure 1.6 . Each of the three stacked bars refers to 10-year periods and indicates how the net change in CO₂ emissions of that decade can be attributed to the four indicators of the Kaya identity. These contributions – to tonnes of CO₂ emissions – can be positive or negative, and their sum equals the net emission change (shown for each decade by the black line).

Figure 1.6: Decomposition of global energy-related CO₂ emission changes at the global scale for three historical and three future decades.

Sources: IEA data World Energy Outlook 2006 ( IEA, 2006a [NPR] )

GDP/capita and population growth were the main drivers of the increase in global emissions during the last three decades of the 20th century. However, consistently declining energy intensities indicate structural changes in the global energy system. The role of carbon intensity in offsetting emission growth has been declining over the last two decades. The reduction in carbon intensity of energy supply was the strongest between 1980 and 1990 due to the delayed effect of the oil price shocks of the 1970 s, and it approached zero towards the year 2000 and reversed after 2000 At the global scale, declining carbon and energy intensities have been unable to offset income effects and population growth and, consequently, carbon emissions have risen. Under the reference scenario of the International Energy Agency ( IEA, 2006a [NPR] ) these trends are expected to remain valid until 2030; in particular, energy is not expected to be further decarbonized under this baseline scenario.

Of the major countries and groups of countries – North America, Western Europe, Japan, China, India, Brazil, Transition Economies – only the Transition Economies (refers to 1993 – 2003 only) and, to a lesser extent, the group of the EU15 have reduced their CO₂ emissions in absolute terms.

The decline of the carbon content of energy (CO₂/TPES) was the highest in Western Europe, but the effect led only to a slight reduction of CO₂ in absolute terms. Together with Western Europe and the Transition Countries, USA/Canada, Japan and – to a much lesser extent – Brazil have also reduced their carbon intensity.

Declining energy intensities observed in China and India have been partially offset by increasing carbon intensities (CO₂/TPES) in these countries. It appears that rising carbon intensities accompany the early stages of the industrialization process, which is closely linked to accelerated electricity generation mainly based on fossil fuels (primarily coal). In addition, the emerging but rapidly growing transport sector is fuelled by oil, which further contributes to increasing carbon intensities. Stepped-up fossil fuel use, GDP/capita growth and, to a lesser extent, population growth have resulted in the dramatic increase in carbon emissions in India and China.

The Transition Economies of Eastern Europe and the former Soviet Union suffered declining per capita incomes during the 1990 s as a result of their contracting economies and, concurrently, total GHG emissions were greatly reduced. However, the continued low level of energy efficiency in using coal, oil and gas has allowed only moderate improvements in carbon and energy intensities. Despite the economic decline during the 1990 s, this group of countries accounted for 12% of global CO₂ emissions in 2003 ( Marland et al., 2006 [NPR] ).

The challenge – an absolute reduction of global GHG emissions – is daunting. It presupposes a reduction of energy and carbon intensities at a faster rate than income and population growth taken together. Admittedly, there are many possible combinations of the four Kaya identity components, but with the scope and legitimacy of population control subject to ongoing debate, the remaining two technology-oriented factors, energy and carbon intensities, have to bear the main burden.

1.3.2 Future outlook

1.3.2.2 CO₂ emissions

Global growth in fossil fuel demand has a significant effect on the growth of energy-related CO₂ emissions: both the IEA and the U.S. EIA project growth of more than 55% in their respective forecast periods. The IEA projects a 1.7% per year growth rate to 2030, while the U.S. EIA projects a 2.0% per year rate in the absence of additional policies. According to IEA projections, emissions will reach 40.4 GtCO₂ in 2030, an increase of 14.3 GtCO₂ over the 2004 level. SRES ^[14] ( IPCC, 2000a [NPR] ) CO₂ emissions from energy use for 2030 are in the range 37.2–53.6 GtCO₂, which is similar to the levels projected in the EMF-21 ^[15] ( EMF, 2004 [NPR, MoS] ) scenarios reviewed in Chapter 3 , Section 3.2.2 (35.9–52.1 GtCO₂). Relative to the approximately 25.5 GtCO₂ emissions in 2000 (see Fig 1.1), fossil fuel-sourced CO₂ emissions are projected to increase by 40–110% by 2030 in the absence of climate policies in these scenarios (see Figure 1.7 ).

Figure 1.7 Global GHG emissions for 2000 and projected baseline emissions for 2030 and 2100 from IPCC SRES and the post-SRES literature. The figure provides the emissions from the six illustrative SRES scenarios. It also provides the frequency distribution of the emissions in the post-SRES scenarios (5th, 25th, median, 75th, 95th percentile), as covered in Chapter 3 . F-gases include HFCs, PFCs and SF₆

As the bulk of the growing energy demand occurs in developing countries, the CO₂ emission growth accordingly is dominated by developing countries. The latter would contribute two thirds to three quarters of the IEA-projected increase in global energy-related emissions. Developing countries, which accounted for 40% of total fossil fuel-related CO₂ emissions in 2004, are projected to overtake the Organization for Economic Co-operation and Development (OECD) as the leading contributor to global CO₂ fossil fuel emissions in the early part of the next decade.

The CO₂ emission projections account for both growth in energy demand and changes in the fuel mix. The IEA projects the share of total energy-related emissions accounted for by gas to increase from 20% in 2004 to 22% in 2030, while the share of coal increases from 41% to 43% and oil drops by approximately 4%, from 39% to 35%, respectively, of the total. On the basis of sectoral shares at the global level, power generation grows from a 41% to a 44% share, while the 20% share of transport is unchanged. The fastest emissions growth rate is in power generation – at 2.0% per year – followed by transport at 1.7% per year. The industry sector grows at 1.6% per year, the residential/commercial sector at 1% per year and international marine and aviation emissions at 0.7% per year.

The SRES range of energy-related CO₂ emissions for 2100 is much larger, 15.8–111.2 GtCO₂, while the EMF-21 scenario range for 2100 is 53.6–101.4 GtCO₂.

1.3.3 Technology research, development and deployment: needs and trends

1.4.1 UNFCCC and its Kyoto Protocol

• Equity, which is expressed as “common but differentiated responsibilities” that assigns the lead in mitigation to developed countries (Article 3.1) and that takes the needs and special circumstances of developing countries into account (Article 3.2).
• A precautionary principle, which says that “where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing such measures, taking into account that policies and measures to deal with climate change should be cost-effective so as to ensure global benefits at the lowest possible cost” (Article 3.3).
• A right to and an obligation to promote sustainable development (Article 3.4).
• An obligation to cooperate in sharing information about climate change, technologies through technology transfers, and the coordination of national actions (Article 3.7)

Based on the principle of common but differentiated responsibilities, Annex I countries are committed to adopt policies and measures aimed at returning – individually or jointly – their GHG emissions to earlier levels by the year 2000 (Article 4.2). Following the decision of the first Conference of the Parties ^[17] (COP1) in Berlin in 1995 that these commitments were inadequate, the Kyoto Protocol was negotiated and adopted by consensus at COP3, in Kyoto in 1997, and entered into force on 16 February 2005 . This was preceded by the detailed negotiation of the implementing rules and agreements for the Protocol – the Marrakech Accords – that were concluded at COP7 in Marrakech and adopted in Montreal at CMP1 ^[18] . As of December 2006, the Protocol has been ratified by 165 countries. While Australia and the United States, both parties to UNFCCC, signed the protocol, both have stated an intention not to ratify.

Several key features of the Protocol are relevant to the issues raised later in this report:

• Each Party listed in Annex B of the Protocol is assigned a legally binding quantified GHG emission limitation and/or reduction measured in CO₂ equivalents for the first commitment period 2008–2012. In aggregate, these Parties are expected to reduce their overall GHG emissions by “at least 5 per cent below 1990 levels in the commitment period 2008 to 2012” (Article 3.1). Some flexibility is shown towards economies in transition who may nominate a base year or period other than 1990 (Article 3.5, 3.7).
• Six classes of gases are listed in Annex A of the Protocol: CO₂, CH₄, N₂O, HFCs, PFCs and SF₆. Emissions from international aviation and maritime transport are not included.
• The so-called Kyoto flexibility mechanisms allow Annex B Parties to obtain emission allowances achieved outside their national borders but supplemental to domestic action, which is expected to be a “significant element of the effort” (Article 6.1 (d), Article17, CMP1 ^[19] ). These mechanisms are: an international emission trading system, Joint Implementation (JI) projects in Economies in Transition, projects undertaken as of year 2000 in developing (non-Annex I) countries under the Clean Development Mechanism (CDM) and carbon sink projects in Annex B countries.
• A set of procedures for emission monitoring, reporting, verification and compliance has been adopted at CMP1 under Articles 5, 7, 8 and 18.

In accordance with Article 3.9, the Parties to the Protocol at CMP1 began the process of negotiating commitments for the Annex B Parties for the second commitment period, creating – the ‘Ad Hoc Working Group on Further Commitments for Annex I Parties under the Kyoto Protocol’ (AWG), with the requirement that negotiations be completed so that that the first and second commitment periods are contiguous. Work continued at CMP2 in Nairobi and in 2007 the AWG will work on, amongst other thing, ranges of emission reduction objectives of Annex I Parties with due attention to the conditions mentioned in Article 2 of the Convention (see 1.2.1). The task is to consider that “according to the scenarios of the TAR, global emissions of carbon dioxide have to be reduced to very low levels, well below half of levels in 2000, in order to stabilize their concentrations in the atmosphere” (see Chapters 3 and 13 ).

In addition, CMP2 started preparations for the second review of the Protocol under Article 9, which in principle covers all aspects of the Protocol, and set 2008 as the date for this review.

Under the UNFCCC, a Dialogue on Long-Term Cooperation Action to Address Climate Change by Enhancing Implementation of the Convention (the Dialogue) was established at COP11 in 2005, met during 2006 and is to conclude at COP13 in 2007 . The Dialogue is “without prejudice to any future negotiations, commitments, process, framework or mandate under the Convention, to exchange experiences and analyse strategic approaches for long-term cooperative action to address climate change”.

1.4.2 Technology cooperation and transfer

Effective and efficient mitigation of climate change depends on the rate of global diffusion and transfer of new as well as existing technologies. To share information and development costs, international cooperation initiatives for RDDD&D, such as the Carbon Sequestration Leadership Forum (CSLF), the International Partnership for Hydrogen Economy (IPHE), the Generation IV International Forum (GIF), the Methane to Markets Partnership and the Renewable Energy & Energy Efficiency Partnership (REEEP), the Global Bioenergy Partnership and the ITER fusion project, were undertaken. Their mandates range from basic R&D and market demonstration to barrier removals for commercialization/diffusion. In addition, there are 40 ‘implementing agreements’ facilitating international cooperation on RDDD&D under IEA auspices, covering all of the key new technologies of energy supply and end use with the exception of nuclear fission ( IEA, 2005 [NPR] ).

Regional cooperation may be effective as well. Asia-Pacific Partnership of Clean Development and Climate (APPCDC), which was established by Australia, China, India, Japan, Korea and the USA in January 2006, aims to address increased energy needs and associated challenges, including air pollution, energy security, and climate change, by enhancing the development, deployment and transfer of cleaner, more efficient technologies. In September 2005, the EU concluded agreements with India and China, respectively, with the aim of promoting the development of cleaner technologies (India) and low carbon technologies (China).

Bilateral sector-based cooperation agreements also exist. One example is the Japan/China agreement on energy efficiency in the steel industry, concluded in July 2005 JISF,Bilateral sector-based cooperation agreements also exist. One example is the Japan/China agreement on energy efficiency in the steel industry, concluded in July 2005 JISF,). These sector-based initiatives may be an effective tool for technology transfer and mitigating GHG emissions.

It is expected that CDM and JI under the Kyoto Protocol will play important role for technology transfer as well.

1.5.1 Previous assessments

The IPCC was set up in 1988 by UNEP and WMO with three working groups: to assess available scientific information on climate change (WGI), to assess environmental and socio-economic impacts (WGII) and to formulate response strategies (WGIII).

The First Assessment Report (FAR) ( IPCC, 1991 [NPR] ) dealt with the anthropogenic alteration of the climate system through CO₂ emissions, potential impacts and available cost-effective response measures in terms of mitigation, mainly in the form of carbon taxes without much concern for equity issues ( IPCC, 2001 [NPR] , Chapter 1).

For the Second Assessment Report (SAR), in 1996, Working Groups II and III were reorganized ( IPCC, 1996 [NPR] ). WGII dealt with adaptation and mitigation, and WGIII dealt with the socio-economic cross-cutting issues related to costing climate change’s impacts and providing cost-benefit analysis (CBA) for use in decision-making. The socio-institutional context was emphasized as well as the issues of equity, development, and sustainability ( IPCC, 2001 [NPR] , Chapter 1).

For the Third Assessment Report (TAR) ( IPCC, 2001 [NPR] ), Working Groups II and III were again reorganized to deal with adaptation and mitigation, respectively. The concept of mitigative capacity was introduced, and the focus attention was shifted to sustainability concerns ( IPCC, 2001 [NPR] , Chapter 1.1). Four cross-cutting issues were identified: costing methods, uncertainties, decision analysis frameworks and development, equity and sustainability ( IPCC, 2000b [NPR] ).

The Fourth Assessment Report (AR4) summarizes the information contained in previous IPCC reports - including the IPCC special reports on Carbon Dioxide Capture and Storage, on Safeguarding the Ozone Layer and on the Global Climate System published since TAR - and assesses the scientific literature published since 2000 .

Although the structure of AR4 resembles the macro-outline of the TAR, there are distinct differences between them. The AR4 assigns greater weight to (1) a more detailed resolution of sectoral mitigation options and costs; (2) regional differentiation; (3) emphasizing previous and new cross-cutting issues, such as risks and uncertainties, decision- and policy-making, costs and potentials and the relationships between mitigation, adaptation and sustainable development, air pollution and climate, regional aspects and the issues related to the implementation of UNFCCC Article 2; and (4) the integration of all these aspects.

1.5.2 Roadmap

This report assesses options for mitigating climate change. It has four major parts, A–D.

Part A comprises Chapter 1 , an Introduction and Chapter 2 , which is on ‘framing issues’. Chapter 2 introduces the report’s cross-cutting themes, which are listed above, and outlines how these themes are treated in subsequent chapters. It also introduces important concepts (e.g. cost-benefit analysis and regional integration) and defines important terms used throughout the report.

Part B consists of one chapter, Chapter 3 . This chapter reviews and analyzes baseline (non-mitigation) and stabilization scenarios in the literature that have appeared since the publications of the IPCC SRES and the TAR. It pays particular attention to the literature that criticizes the IPCC SRES scenarios and concludes that uncertainties and baseline emissions have not changed very much. It discusses the driving forces for GHG emissions and mitigation in the short and medium terms and emphasizes the role of technology relative to social, economic and institutional inertia. It also examines the relation between adaptation, mitigation and avoided climate change damage in the light of decision-making on atmospheric GHG concentrations (Article 2 UNFCCC).

Part C consists of seven chapters, each of which assesses sequence mitigation options in different sectors. Chapter 4 addresses the energy supply sector, including carbon capture and storage; Chapter 5 transport and associated infrastructures; Chapter 6 the residential, commercial and service sectors; Chapter 7 the industrial sector, including internal recycling and the reuse of industrial wastes; Chapters 8 and 9 the agricultural and forestry sectors, respectively, including land use and biological carbon sequestration; Chapter 10 waste management, post-consumer recycling and reuse.

These seven chapters use a common template and cover all relevant aspects of GHG mitigation, including costs, mitigation potentials, policies, technology development, technology transfer, mitigation aspects of the three dimensions of sustainable development, system changes and long-term options. They provide the integrated picture that was absent in the TAR. Where supporting literature is available, they address important differences across regions.

Part D comprises three chapters (11–13) that focus on major cross-sectoral considerations. Chapter 11 assesses the aggregated short-/medium-term mitigation potential, macro-economic impacts, economic instruments, technology development and transfer and cross-border influences (or spill-over effects). Chapter 12 links climate mitigation with sustainable development and assesses the GHG emission impacts of implementing the Millennium Development Goals and other sustainable development policies and targets. Chapter 13 assesses domestic climate policy instruments and the interaction between domestic climate policies and various forms of international cooperation and reviews climate change as a global common issue in the context of sustainable development objectives and policies. It summarizes relevant treaties, cooperative development agreements, private–public partnerships and private sector initiatives and their relationship to climate objectives.