|445〜490||2000〜15||-85 〜 -50||1.4〜1.8||（3未満）||（5.5未満）|
|490〜535||2000〜20||-60 〜 -30||1.8〜2.2||（3未満）||（5.5未満）|
|535〜590||2000〜30||-35 〜 + 5||2.2〜2.6||(550ppm) 20〜80ドル||0.6（0.2〜2.5）||1.3（〜4）|
|590〜710||2000〜60||+10 〜 +60||2.6〜3.4||(650ppm) 0〜30ドル||0.2（0.6〜1.2）||0.5（-1〜2）|
|710〜855||2000〜80||+25 〜 +85||3.4〜4.3||(750ppm) 0〜20ドル|
|855〜1130||2000〜90||+90 〜 +140||4.3〜5.5|
2007/5/4 New York
Beating Global Warming Need Not Cost the Earth: U.N.
``It's a great report and it's very strong and it shows that it's economically and technically feasible to make deep emission reductions sufficient to limit warming to 2 degrees,'' he said. ``It shows that the costs of doing this are quite modest.''
To keep within the 2 degree threshold which scientists say is needed to stave off disastrous changes to the world's climate, emissions of carbon dioxide need to drop between 50 and 85 percent by 2050, the report said.
In 2030 the costs for limiting greenhouse gases at ''stabilization'' levels of between 445 and 710 ppm (parts per million) CO2-equivalent range from a 3 percent decrease of global GDP to a small increase, it said.
Greenhouse gas concentrations are now at about 430 ppm CO2-equivalent.
IPCC Fourth Assessment
Report The Working Group III 2007/5/4
|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) .|
|・||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).|
|・||Baseline emissions scenarios published since SRES, are comparable in range to those presented in the IPCC Special Report on Emission Scenarios (SRES) (25- 135 GtCO2-eq/yr in 2100, see Figure SPM.4). (high agreement, much evidence)|
|Mitigation in the short and medium term (until 2030)|
bottom-up and top-down studies indicate that there is substantial
economic potential for the mitigation of global GHG
over the coming decades, that could offset the projected
growth of global emissions or reduce emissions below
current levels (high agreement, much evidence).
Key mitigation technologies and practices by sector
|・||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. However, regional costs may differ significantly from global averages(high agreement, medium evidence)|
|・||Changes in lifestyle and behaviour patterns can contribute to climate change mitigation across all sectors. Management practices can also have a positive role. (high agreement, medium evidence)|
|・||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).|
|・||Literature since TAR confirms that there may be effects from Annex I countries （気候変動枠組条約の付属書 I に記載される国々。2000までに温室効果ガスの排出量を1990年レベルに減少させることが義務付けられている。）action on the global economy and global emissions, although the scale of carbon leakage remains uncertain (high agreement, medium 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).|
|・||There are multiple mitigation options in the transport sector , but their effect may be counteracted by growth in the sector. Mitigation options are faced with many barriers, such as consumer preferences and lack of policy frameworks (medium agreement, medium evidence).|
|・||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).|
|・||The economic potential in the industrial sector is predominantly located in energy intensive industries. Full use of available mitigation options is not being made in either industrialized or developing nations (high agreement, much evidence).|
|・||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).|
|・||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) .|
|・||Post-consumer waste is a small contributor to global GHG emissions (<5%), but the waste sector can positively contribute to GHG mitigation at low cost and promote sustainable development (high agreement, much evidence).|
|・||Geo-engineering options, such as ocean fertilization to remove CO2 directly from the atmosphere, or blocking sunlight by bringing material into the upper atmosphere, remain largely speculative and unproven, and with the risk of unknown side-effects. Reliable cost estimates for these options have not been published (medium agreement, limited evidence)|
|Mitigation in the long term (after 2030)|
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 (high agreement, much
|Stabilization scenario categories as reported in Figure SPM.7 (coloured bands) and their relationship to equilibrium global mean temperature change above pre-industrial, using (i) “best estimate” climate sensitivity of 3°C (black line in middle of shaded area), (ii) upper bound of likely range of climate sensitivity of 4.5°C (red line at top of shaded area) (iii) lower bound of likely range of climate sensitivity of 2°C (blue line at bottom of shaded area). Coloured shading shows the concentration bands for stabilization of greenhouse gases in the atmosphere corresponding to the stabilization scenario categories I to VI as indicated in Figure SPM.7.|
|・||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).|
|・||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. For specific countries and sectors, costs vary considerably from the global average. (high agreement, medium evidence).|
|・||Decision-making about the appropriate level of global mitigation over time involves an iterative risk management process that includes mitigation and adaptation, taking into account actual and avoided climate change damages, co-benefits, sustainability, equity, and attitudes to risk. Choices about the scale and timing of GHG mitigation involve balancing the economic costs of more rapid emission reductions now against the corresponding medium-term and long-term climate risks of delay [high agreement, much evidence].|
|Policies, measures and instruments to mitigate climate change|
|A wide variety of national policies and instruments are available to governments to create the incentives for mitigation action. Their applicability depends on national circumstances and an understanding of their interactions, but experience from implementation in various countries and sectors shows there are advantages and disadvantages for any given instrument (high agreement, much evidence).|
|・||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)|
sectoral policies, measures and instruments that have
shown to be environmentally effective in the respective
sector in at least a number of national cases.
|・||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).|
|・||Notable achievements of the UNFCCC and its Kyoto protocol are the establishment of a global response to the climate problem, stimulation of an array of national policies, the creation of an international carbon market and the establishment of new institutional mechanisms that may provide the foundation for future mitigation efforts (high agreement, much evidence).|
|・||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).|
|Sustainable development and climate change mitigation|
|・||Making development more sustainable by changing development paths can make a major contribution to climate change mitigation, but implementation may require resources to overcome multiple barriers. There is a growing understanding of the possibilities to choose and implement mitigation options in several sectors to realize synergies and avoid conflicts with other dimensions of sustainable development (high agreement, much evidence).|
|Gaps in knowledge|
|There are still relevant gaps in currently available knowledge regarding some aspects of mitigation of climate change, especially in developing countries. Additional research addressing those gaps would further reduce uncertainties and thus facilitate decision-making related to mitigation of climate change.|