Mitigation of Global Warming

Climate change mitigation are actions to limit the magnitude and/or rate of long-term climate change.[2] Climate change mitigation generally involves reductions in human (anthropogenic) emissions of greenhouse gases (GHGs).[3] Mitigation may also be achieved by increasing the capacity of carbon sinks, e.g., through reforestation.[3] By contrast, adaptation to global warming are actions taken to manage the eventual (or unavoidable) impacts of global warming,[4] e.g., by building dikes in response to sea level rise.[5]

Examples of mitigation include switching to low-carbon energy sources, such as renewable and nuclear energy, and expanding forests and other "sinks" to remove greater amounts of carbon dioxide from the atmosphere.[3] Energy efficiency can also play a major role,[6] for example, through improving the insulation of buildings.[7]

Another approach to climate change mitigation is geoengineering.[8] Most geoengineering techniques can be organized into two categories.[9] The first category is called solar radiation management, which involves either reducing incoming sunlight, or increasing the reflectivity (albedo) of the Earth's surface to sunlight.[9] The second category is called carbon dioxide removal, which involves reducing the atmospheric concentration of carbon dioxide, e.g., by increasing the capacity of the oceans to absorb carbon from the atmosphere.[9] Scientific understanding of geoengineering is limited, and there is the risk of unknown side-effects.[10]

The main international treaty on climate change is the United Nations Framework Convention on Climate Change (UNFCCC).[11] In 2010, Parties to the UNFCCC agreed that future global warming should be limited to below 2.0 °C (3.6 °F) relative to the pre-industrial level.[12] Analysis suggests that meeting the 2 °C target would require annual global emissions of greenhouse gases[13] to peak before the year 2020, and decline significantly thereafter,[14] with emissions in 2050 reduced by 30-50% compared to 1990 levels.[15] Analyses by the United Nations Environment Programme[16] and International Energy Agency[17] suggest that current policies (as of 2012) are too weak to achieve the 2 °C target.


Greenhouse gas concentrations and stabilization

Stabilizing CO2 emissions at their present level would not stabilize its concentration in the atmosphere.[18]
Stabilizing the atmospheric concentration of CO2 at a constant level would require emissions to be effectively eliminated.[18]


There are a number of anthropogenic greenhouse gases. These include carbon dioxide (chemical formula: CO2), methane (), nitrous oxide (), and a group of gases referred to as halocarbons.[20] The emissions reductions necessary to stabilize the atmospheric concentrations of these gases varies.[18] CO2 is the most important of the anthropogenic greenhouse gases (see radiative forcing).[21]

There is a difference between stabilizing CO2 emissions and stabilizing atmospheric concentrations of CO2.[22] Stabilizing emissions of CO2 at current levels would not lead to a stabilization in the atmospheric concentration of CO2. In fact, stabilizing emissions at current levels would result in the atmospheric concentration of CO2 continuing to rise over the 21st century and beyond (see the graphs opposite).

The reason for this is that human activities are adding CO2 to the atmosphere far faster than natural processes can remove it (see carbon dioxide in Earth's atmosphere for a more complete explanation).[18] This is analogous to a flow of water into a bathtub.[23] So long as the tap runs water (analogous to the emission of carbon dioxide) into the tub faster than water escapes through the plughole (the natural removal of carbon dioxide from the atmosphere), then the level of water in the tub (analogous to the concentration of carbon dioxide in the atmosphere) will continue to rise.

Stabilizing atmospheric CO2 concentrations would require anthropogenic CO2 emissions to be reduced by 80% relative to the peak emissions level.[24] An 80% reduction in emissions would stabilize CO2 concentrations for around a century, but even greater reductions would be required beyond this.[24][18]

Stabilizing the atmospheric concentration of the other greenhouse gases humans emit also depends on how fast their emissions are added to the atmosphere, and how fast the GHGs are removed. Stabilization for these gases is described in the later section on non-CO2 GHGs.


Projections of future greenhouse gas emissions are highly uncertain.[25] In the absence of policies to mitigate climate change, GHG emissions could rise significantly over the 21st century.[26]

Numerous assessments have considered how atmospheric GHG concentrations could be stabilized.[27] The lower the desired stabilization level, the sooner global GHG emissions must peak and decline.[28] GHG concentrations are unlikely to stabilize this century without major policy changes.[26]

Energy consumption by power source

To create lasting climate change mitigation, the replacement of high carbon emission intensity power sources, such as conventional fossil fuels - oil, coal and natural gas - with low-carbon power sources is required. Presently fossil fuels supply humanity with the vast majority of our energy demands, and at a growing rate. In 2012 the IEA noted that coal accounted for half the increased energy use of the prior decade, growing faster than all renewable energy sources.[30] Both hydroelectricity and nuclear power together provide the majority of the generated low-carbon power fraction of global total power consumption.

Fuel type Average total global power consumption in TW[31]
1980 2004 2006
Oil 4.38 5.58 5.74
Gas 1.80 3.45 3.61
Coal 2.34 3.87 4.27
Hydroelectric 0.60 0.93 1.00
Nuclear power 0.25 0.91 0.93
Geothermal, wind,
solar energy, wood
0.02 0.13 0.16
Total 9.48 15.0 15.8
Source: The USA Energy Information Administration
Change and use of energy, by source, in units of (PWh) in that year.[32]
Fossil Nuclear All renewables Total
1990 83.374 6.113 13.082 102.569
2000 94.493 7.857 15.337 117.687
2008 117.076 8.283 18.492 143.851
Change 2000–2008 22.583 0.426 3.155 26.164

Methods and means


Other frequently discussed means include energy conservation, increasing fuel economy in automobiles (which includes the use of electric hybrids), charging plug-in hybrids and electric cars by low-carbon electricity, making individual-lifestyle changes[35] (e.g., cycling instead of driving),[36] and changing business practices.

A range of energy technologies may contribute to climate change mitigation.[37] These include renewable energy sources such as solar power, tidal, ocean energy, geothermal power, and wind power; nuclear power, the use of carbon sinks, and carbon capture and storage. For example, Pacala and Socolow of Princeton [38] have proposed a 15 part program to reduce CO2 emissions by 1 billion metric tons per year − or 25 billion tons over the 50-year period using today's technologies as a type of Global warming game.[39]

Another consideration is how future socio-economic development proceeds. Development choices (or "pathways") can lead differences in GHG emissions.[40] Political and social attitudes may affect how easy or difficult it is to implement effective policies to reduce emissions.[41]

Alternative energy sources

Renewable energy

In 2011, the share of renewables in electricity generation worldwide grew for the fourth year in a row to 20.2%, with the global share of electricity from hydro power staying roughly constant at 16.3%.[42]

Climate change concerns[43][44][45] and the need to reduce carbon emissions are driving increasing growth in the renewable energy industries.[46][47][48] Some 85 countries now have targets for their own renewable energy futures, and have enacted wide-ranging public policies to promote renewables.[49][50] Low-carbon renewable energy replaces conventional fossil fuels in three main areas: power generation, hot water/ space heating, and transport fuels.[51]

In 2009 Mark Z. Jacobson and colleagues published a plan to power 100% of the world's energy with wind power, hydroelectric, and solar power by the year 2030.[52][53] The authors estimate the cost of the system, over twenty years, might be on the order of US$100 trillion (not including transmission wire costs),[54] with wind farms occupying one percent of the earth's land surface area, and the non-rooftop photovoltaics and concentrated solar power plants occupying about 0.33 percent of the earth's land surface area.[55] In 2010 they estimate that approximately 3.8 million, 5 MW wind turbines, 49 thousand, 300 MW concentrated solar plants, 40 thousand 300 MW solar PV power plants, 1.7 billion 3 kW rooftop PV systems, 5 thousand 100 MW geothermal power plants, and three hundred new 1300 MW hydroelectric power plants will be needed. The authors also argue that this plan will reduce infrastructure and world power demand by 30%, and that it will require 0.41% and 0.59% more of the Earth's land for footprint and spacing, respectively.[56]

NASA Climate scientist James Hansen has said that while it is conceivable in places such as New Zealand and Norway, "suggesting that renewables will let us phase rapidly off fossil fuels in the United States, China, India, or the world as a whole is almost the equivalent of believing in the Easter Bunny and Tooth Fairy."[57][58] In 2012, scientist and policy analyst Vaclav Smil analyzed proposals to depend on wind- and solar-generated electricity including the proposals of Mark Z. Jacobson and colleagues, and he identified numerous points of concern, such as cost, intermittent power supply, growing NIMBYism and a lack of infrastructure as negative factors and said that "History and a consideration of the technical requirements show that the problem is much greater than these advocates have supposed."[59]

Controversy surrounding the present classification of all biomass as "renewable energy", may lead to an increase in the emission of greenhouse gases in the short to medium term, as it can take from 2 to 100 years for different sources of plant energy to regrow, such as the difference between fast growing switch grass and slow growing trees, and due to the high emission intensity of plant material, researchers have suggested that if the biomass source takes longer than 20 years to regrow, they argue the plant source should not be regarded as renewable from a climate change mitigation standpoint.[60]


Some countries, with favorable geography, geology and weather well suited to an economical exploitation of renewable energy sources, get most of their electricity from renewables, including from geothermal energy in Iceland (100 percent), and Hydroelectric power in Brazil (85 percent), Austria (62 percent), New Zealand (65 percent), and Sweden (54 percent).[62] Renewable power generators are spread across many countries, with wind power providing a significant share of electricity in some regional areas: for example, 14 percent in the U.S. state of Iowa, 40 percent in the northern German state of Schleswig-Holstein, and 20 percent in Denmark. Solar water heating makes an important and growing contribution in many countries, most notably in China, which now has 70 percent of the global total (180 GWth). Worldwide, total installed solar water heating systems meet a portion of the water heating needs of over 70 million households. The use of biomass for heating continues to grow as well. In Sweden, national use of biomass energy has surpassed that of oil. Direct geothermal heating is also growing rapidly.[62] Renewable biofuels for transportation, such as ethanol fuel and biodiesel, have contributed to a significant decline in oil consumption in the United States since 2006. The 93 billion liters of biofuels produced worldwide in 2009 displaced the equivalent of an estimated 68 billion liters of gasoline, equal to about 5 percent of world gasoline production.[62]

Nuclear power

A Yale University review published in the Journal of Industrial Ecology analyzing CO2 life cycle assessment emissions from nuclear power determined that:[63]


Nuclear power, with as of 2007, a 20% share of U.S. electricity production, is the single largest deployed low-carbon power technology.[64]

Nuclear power, as of 2010, also provides two thirds(2/3) of the twenty seven nation European Union's low-carbon power.[65]

In 2007, nuclear power supplied around 15% of the world's electricity.[66] Numerous studies and assessments (e.g., by the Intergovernmental Panel on Climate Change (IPCC),[67] International Atomic Energy Agency,[68] and International Energy Agency)[69] suggest that as part of the portfolio of other low-carbon energy technologies, nuclear power will continue to play a role in reducing greenhouse gas emissions. Historically, nuclear power usage is estimated to have prevented the atmospheric emission of 64 gigatonnes of CO2-equivalent as of 2013.[70] Public concerns about nuclear power include the fate of spent nuclear fuel, nuclear safety, and security risks which are considered unique among low-carbon energy sources, however many Hydroelectric power stations also have safety and security concerns, with one such safeguard being in the form of the Hoover Dam Police.


Nuclear power may be uncompetitive compared with fossil fuel energy sources in countries without a carbon tax program, and in comparison to a fossil fuel plant of the same power output, nuclear power plants take a longer amount of time to construct.[72][73][74][75]

Uncertainty surrounding the future GHG emissions of nuclear power have to do with the potential for a declining uranium ore grade without a corresponding increase in the efficiency of enrichment methods. In a scenario analysis of future global nuclear development, as it could be effected by a decreasing global uranium market of average ore grade, the analysis determined that depending on conditions, median life cycle nuclear power GHG emissions could be between 9 to 110 g CO2-eq/kWh by 2050.[77]

Two new, first of their kind, EPR reactors under construction in Finland and France have been delayed and are running over-budget.[78][79][80] However learning from experience, two further EPR reactors under construction in China are on, and ahead, of schedule respectively.[81] As of 2013, according to the IAEA and the European Nuclear Society, worldwide there were 68 civil nuclear power reactors under construction in 15 countries.[82][83] China has 29 of these nuclear power reactors under construction, as of 2013, with plans to build many more,[83][84] while in the US the licenses of almost half its reactors have been extended to 60 years,[85] and plans to build another dozen are under serious consideration.[86] There are also a considerable number of new reactors being built in South Korea, India, and Russia. At least 100 older and smaller reactors will "most probably be closed over the next 10-15 years".[87] This is probable only if one does not factor in the ongoing Light Water Reactor Sustainability Program, created to permit the extension of the life span of the USA's 104 nuclear reactors to 60 years. The licenses of almost half of the USA's reactors have been extended to 60 years as of 2008.[85] Two new AP1000 reactors are, as of 2013, being constructed at Vogtle Electric Generating Plant.

Due primarily to France's low greenhouse gas emitting electricity grid, taken as a whole, the total life cycle carbon dioxide emissions from a plug-in electric car recharged by the French electricity grid has been calculated to be approximately 12 grams per kilometer travelled.[88] This compares more favorably than the emissions emitted from one of the most successful hybrid cars, the Toyota Prius, which produces carbon dioxide emissions at the higher rate of 105 grams per kilometer travelled.[88] Nuclear power plants produce approximately 75 percent of all electricity in France, the highest percentage in the world.[89]

Currently, the most popular source of nuclear power is uranium-235. However, thorium in a molten salt reactor has been touted as a more practical alternative to uranium. This is in part because its naturally occurring isotope, thorium-232, is fertile, while uranium needs to be enriched before it can be used in nuclear power applications. One major obstacle to the use of thorium power is that it requires a significant investment in new research and development.[90] Nevertheless, India currently runs a three-stage nuclear process that utilizes thorium power.[91] Norway has also recently announced plans to pursue thorium power.[92]

Nuclear fusion, in the form of the International Thermonuclear Experimental Reactor is predicted to achieve an energy return on investment between 2020 and 2030. With a follow on commercial nuclear fusion power station, DEMO, estimated to be operational by 2030.[93][94] There is also suggestions for a power plant based upon a different fusion approach, that of a Inertial fusion power plant.

Public opinion about nuclear power varies between countries.[95][96] A poll by Gallup International (2011)[97] assessed public opinion in 47 countries. The poll was conducted following a tsumani and earthquake which caused an accident at the Fukushima nuclear power plant in Japan. 49% stated that they held favourable views about nuclear energy, while 43% held an unfavourable view.[98] Another global survey by Ipsos (2011)[99] assessed public opinion in 24 countries. Respondents to this survey showed a clear preference for renewable energy sources over coal and nuclear energy (refer to graph opposite).[76] Ipsos (2012)[100] found that solar and wind were viewed by the public as being more environmentally friendly and more viable long-term energy sources relative to nuclear power and natural gas. However, solar and wind were viewed as being less reliable relative to nuclear power and natural gas.


Carbon intensity of fossil fuels

Most mitigation proposals imply — rather than directly state — an eventual reduction in global fossil fuel production. Also proposed are direct quotas on global fossil fuel production.[102][103]

Fuel switching

Natural gas emits far fewer greenhouse gases (i.e. CO2 and Methane - CH4) than coal when burned at power plants, but evidence has been emerging that this benefit could be completely negated by methane leakage at gas drilling fields and other earlier points in the production lifecycle.



Carbon capture and storage

Carbon capture and storage (CCS) is a method to mitigate climate change by capturing carbon dioxide (CO2) from large point sources such as power plants and subsequently storing it away safely instead of releasing it into the atmosphere. The Intergovernmental Panel on Climate Change says CCS could contribute between 10% and 55% of the cumulative worldwide carbon-mitigation effort over the next 90 years. The International Energy Agency says CCS is "the most important single new technology for CO2 savings" in power generation and industry.[108] Though it requires up to 40% more energy to run a CCS coal power plant than a regular coal plant, CCS could potentially capture about 90% of all the carbon emitted by the plant.[108] Norway, which first began storing CO2, has cut its emissions by almost a million tons a year, or about 3% of the country's 1990 levels.[108] As of late 2011, the total CO2 storage capacity of all 14 projects in operation or under construction is over 33 million tonnes a year. This is broadly equivalent to preventing the emissions from more than six million cars from entering the atmosphere each year.[109]

Energy efficiency and conservation



Energy conservation is broader than energy efficiency in that it encompasses using less energy to achieve a lesser energy service, for example through behavioural change, as well as encompassing energy efficiency. Examples of conservation without efficiency improvements would be heating a room less in winter, driving less, or working in a less brightly lit room. As with other definitions, the boundary between efficient energy use and energy conservation can be fuzzy, but both are important in environmental and economic terms. This is especially the case when actions are directed at the saving of fossil fuels.[113]



Main article: Sustainable transport

Modern energy-efficient technologies, such as plug-in hybrid electric vehicles, and development of new technologies, such as hydrogen cars, may reduce the consumption of petroleum and emissions of carbon dioxide. A shift from air transport and truck transport to electric rail transport would reduce emissions significantly.[116][117]

Increased use of biofuels (such as ethanol fuel and biodiesel that can be used in today's diesel and gasoline engines) could also reduce emissions if produced environmentally efficiently, especially in conjunction with regular hybrids and plug-in hybrids. For electric vehicles, the reduction of carbon emissions will improve further if the way the required electricity is generated is low-carbon power in origin.

Effective urban planning to reduce sprawl would decrease Vehicle Miles Travelled (VMT), lowering emissions from transportation. Increased use of public transport can also reduce greenhouse gas emissions per passenger kilometer.

Urban planning
Main article: Urban planning

Urban planning also has an effect on energy use. Between 1982 and 1997, the amount of land consumed for urban development in the United States increased by 47 percent while the nation's population grew by only 17 percent.[118] Inefficient land use development practices have increased infrastructure costs as well as the amount of energy needed for transportation, community services, and buildings.




Building design

Emissions from housing are substantial,[119] and government-supported energy efficiency programmes can make a difference.[120]



Sinks and negative emissions

Main articles: Carbon sink and Negative carbon dioxide emission

A carbon sink is a natural or artificial reservoir that accumulates and stores some carbon-containing chemical compound for an indefinite period, such as a growing forest. A negative carbon dioxide emission on the other hand is a permanent removal of carbon dioxide out of the atmosphere, such as directly capturing carbon dioxide in the atmosphere and storing it in geologic formations underground.

The Antarctic Climate and Ecosystems Cooperative Research Centre (ACE-CRC) notes that currently one third of humankind’s current present annual emissions of CO2 are absorbed by the oceans. The oceans act as a carbon sink, that is, a reservoir that accumulates and stores carbon via its physicochemical and biological processes.[125] Unfortunately, this "vital service comes with the cost of ocean acidification". The ecological effects of ocean acidification are still largely unknown. Research so far has focussed on how acidification lowers pH and the level of carbonate ions available for calcifying organisms to form their shells. These organisms include plankton species that contribute to the foundation of the Southern Ocean food web. However acidification may impact on a broad range of other physiological and ecological processes, such as fish respiration, larval development and changes in the solubility of both nutrients and toxins.[126] According to the CSIRO [127] the Southern Ocean is absorbing increasing amounts of carbon dioxide, with potentially significant impacts on marine life.[128]

Reforestation and avoided deforestation

Almost 20% (8 GtCO2/year) of total greenhouse-gas emissions were from deforestation in 2007. The Stern Review found that, based on the opportunity costs of the landuse that would no longer be available for agriculture if deforestation were avoided, emission savings from avoided deforestation could potentially reduce CO2 emissions for under $5/tCO2, possiblly as little as $1/tCO2. Afforestation and reforestation could save at least another 1GtCO2/year, at an estimated cost of $5/tCO2 to $15/tCO2.[130] The Review determined these figures by assessing 8 countries responsible for 70% of global deforestation emissions. Pristine temperate forest has been shown to store three times more carbon than IPCC estimates took into account, and 60% more carbon than plantation forest.[131] Preventing these forests from being logged would have significant effects. Further significant savings from other non-energy-related-emissions could be gained through cuts to agricultural emissions, fugitive emissions, waste emissions, and emissions from various industrial processes.[130] Using evidence from Mozambique, a typical low income country where agriculture is the dominant provider of income for most citizens, researchers from the Overseas Development Institute found a positive correlation between increased production intensification and reduced land conversion, and crop returns, economic growth and food security.[132]

Restoring grasslands store CO2 from the air into plant material. Grazing livestock, usually not left to wander, would eat the grass and would minimize any grass growth while grass left alone would eventually grow to cover its own growing buds, preventing them from photosynthesizing and killing the plant.[133] A method proposed to restore grasslands uses fences with many small paddocks and moving herds from one paddock to another after a day a two in order to mimick natural grazers and allowing the grass to grow optimally.[133][134][135] It is estimated that increasing the carbon content of the soils in the world’s 3.5 billion hectares of agricultural grassland by 1% would offset nearly 12 years of CO2 emissions.[133] Allan Savory, as part of holistic management, claims that while large herds are often blamed for desertification, prehistoric lands used to support large or larger herds and areas where herds were removed in the United States are still desertifying.[129]

Negative carbon dioxide emissions

Main article: Negative carbon dioxide emission

Creating negative carbon dioxide emissions literally removes carbon from the atmosphere. Examples are direct air capture, biochar, bio-energy with carbon capture and storage and enhanced weathering technologies. These processes are sometimes considered as variations of sinks or mitigation,[136][137] and sometimes as geoengineering.[138]

In combination with other mitigation measures, sinks in combination with negative carbon emissions are considered crucial for meeting the 350 ppm target,[139][140] and even the less conservative 450 ppm target.[136]


Main article: geoengineering

Geoengineering is seen by some as an alternative to mitigation and adaptation, but by others as an entirely separate response to climate change. In a literature assessment, Barker et al. (2007) described geoengineering as a type of mitigation policy.[141] IPCC (2007) concluded that geoengineering options, such as ocean fertilization to remove CO2 from the atmosphere, remained largely unproven.[142] It was judged that reliable cost estimates for geoengineering had not yet been published.


Carbon dioxide removal

Main articles: Carbon dioxide removal, Greenhouse gas remediation and Carbon sequestration


It is notable that the availability of cheap energy and appropriate sites for geological storage of carbon may make carbon dioxide air capture viable commercially. It is, however, generally expected that carbon dioxide air capture may be uneconomic when compared to carbon capture and storage from major sources — in particular, fossil fuel powered power stations, refineries, etc. In such cases, costs of energy produced will grow significantly. However, captured CO2 can be used to force more crude oil out of oil fields, as Statoil and Shell have made plans to do.[145] CO2 can also be used in commercial greenhouses, giving an opportunity to kick-start the technology. Some attempts have been made to use algae to capture smokestack emissions,[146] notably the GreenFuel Technologies Corporation, who have now shut down operations.[147]

Solar radiation management


Societal controls



Various organizations promote population control as a means for mitigating global warming.[149][150][151][152][153] Proposed measures include improving access to family planning and reproductive health care and information, reducing natalistic politics, public education about the consequences of continued population growth, and improving access of women to education and economic opportunities.

Population control efforts are impeded by there being somewhat of a taboo in some countries against considering any such efforts.[154] Also, various religions discourage or prohibit some or all forms of birth control.


Non-CO2 greenhouse gases

CO2 is not the only GHG relevant to mitigation,[156] and governments have acted to regulate the emissions of other GHGs emitted by human activities (anthropogenic GHGs). The emissions caps agreed to by most developed countries under the Kyoto Protocol regulate the emissions of almost all the anthropogenic GHGs.[157] These gases are CO2, methane (chemical formula: CH4), nitrous oxide (N2O), the hydrofluorocarbons (abbreviated HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).


Methane is a significantly more powerful greenhouse gas than carbon dioxide. Burning one molecule of methane generates one molecule of carbon dioxide, indicating there may be no net benefit in using gas as a fuel source.[104][106] Reducing the amount of waste methane produced in the first place and moving away from use of gas as a fuel source will have a greater beneficial impact, as might other approaches to productive use of otherwise-wasted methane. In terms of prevention, vaccines are in the works in Australia to reduce significant global warming contributions from methane released by livestock via flatulence and eructation.[158]


Although not designed for this purpose, the Montreal Protocol has probably benefitted climate change mitigation efforts.[161] The Montreal Protocol is an international treaty that has successfully reduced emissions of ozone-depleting substances (e.g., CFCs), which are also greenhouse gases.

Costs and benefits


The Stern Review proposes stabilising the concentration of greenhouse-gas emissions in the atmosphere at a maximum of 550ppm CO2e by 2050. The Review estimates that this would mean cutting total greenhouse-gas emissions to three quarters of 2007 levels. The Review further estimates that the cost of these cuts would be in the range −1.0 to +3.5% of World GDP, (i.e. GWP), with an average estimate of approximately 1%.[130] Stern has since revised his estimate to 2% of GWP.[162] For comparison, the Gross World Product (GWP) at PPP was estimated at $74.5 trillion in 2010,[163] thus 2% is approximately $1.5 trillion. The Review emphasises that these costs are contingent on steady reductions in the cost of low-carbon technologies. Mitigation costs will also vary according to how and when emissions are cut: early, well-planned action will minimise the costs.[130]





One of the aspects of mitigation is how to share the costs and benefits of mitigation policies. There is no scientific consensus over how to share these costs and benefits (Toth et al., 2001).[165] In terms of the politics of mitigation, the UNFCCC's ultimate objective is to stabilize concentrations of GHG in the atmosphere at a level that would prevent "dangerous" climate change (Rogner et al., 2007).[166] There is, however, no widespread agreement on how to define "dangerous" climate change.


Distributing emissions abatement costs


  • Basic needs and Rawlsian criteria: this system would have emissions allocated according to basic needs, as defined according to a minimum level of consumption. Consumption above basic needs would require countries to buy more emission rights. This can be related to Rawlsian philosophy. From this viewpoint, developing countries would need to be at least as well off under an emissions control regime as they would be outside the regime.

Specific proposals

  • Ad hoc: Lashof (1992) and Cline (1992) (referred to by Banuri et al., 1996, p. 106),[167] for example, suggested that allocations based partly on GNP could be a way of sharing the burdens of emission reductions. This is because GNP and economic activity are partially tied to carbon emissions.

Governmental and intergovernmental action


Kyoto Protocol

Main article: Kyoto Protocol


Temperature targets

Actions to mitigate climate change are sometimes based on the goal of achieving a particular temperature target. One of the targets that has been suggested is to limit the future increase in global mean temperature (global warming) to below 2 dc, relative to the pre-industrial level.[170][171] The 2 dc target was adopted in 2010 by Parties to the United Nations Framework Convention on Climate Change.[172] Most countries of the world are Parties to the UNFCCC.[173] The target had been adopted in 1996 by the European Union Council.[174]

Temperature targets


Temperatures have increased by 0.8 °C compared to the pre-industrial level, and another 0.5–0.7 °C is already committed.[177] The 2 °C rise is typically associated in climate models with a carbon dioxide equivalent concentration of 400–500 ppm by volume; the current (April 2011) level of carbon dioxide alone is 393 ppm by volume, and rising at 1-3 ppm annually. Hence, to avoid a very likely breach of the 2 °C target, CO2 levels would have to be stabilised very soon; this is generally regarded as unlikely, based on current programs in place to date.[178][179] The importance of change is illustrated by the fact that world economic energy efficiency is presently improving at only half the rate of world economic growth.[180]

Encouraging use changes

Emissions tax

An emissions tax on greenhouse gas emissions requires individual emitters to pay a fee, charge or tax for every tonne of greenhouse gas released into the atmosphere.[181] Most environmentally related taxes with implications for greenhouse gas emissions in OECD countries are levied on energy products and motor vehicles, rather than on CO2 emissions directly.[181]

Emission taxes can be both cost-effective and environmentally effective.[181] Difficulties with emission taxes include their potential unpopularity, and the fact that they cannot guarantee a particular level of emissions reduction.[181] Emissions or energy taxes also often fall disproportionately on lower income classes. In developing countries, institutions may be insufficiently developed for the collection of emissions fees from a wide variety of sources.[181]

Making the emitting of CO2 illegal

Another option is to replace the emission reduction-positive approach proposed with the Kyoto protocol and its successor with an emitted GHG-negative approach.

Scientist Ken Caldeira has proposed making the emitting of CO2 illegal.[182]


According to Mark Z. Jacobson, a program of subsidization balanced against expected flood costs could pay for conversion to 100% renewable power by 2030.[53] Jacobson, and his colleague Mark Delucchi, suggest that the cost to generate and transmit power in 2020 will be less than 4 cents per kilowatt hour (in 2007 dollars) for wind, about 4 cents for wave and hydroelectric, from 4 to 7 cents for geothermal, and 8 cents per kwh for solar, fossil, and nuclear power.[52]

Carbon emissions trading


However, emissions trading may delay the phase-out of fossil fuels.[184]

The European Union Emission Trading Scheme (EU ETS)[185] is the largest multi-national, greenhouse gas emissions trading scheme in the world. It commenced operation on 1 January 2005, and all 25 member states of the European Union participate in the scheme which has created a new market in carbon dioxide allowances estimated at 35 billion Euros (US$43 billion) per year.[186] The Chicago Climate Exchange was the first (voluntary) emissions market, and is soon to be followed by Asia's first market (Asia Carbon Exchange). A total of 107 million metric tonnes of carbon dioxide equivalent have been exchanged through projects in 2004, a 38% increase relative to 2003 (78 Mt CO2e).[187]

Twenty three multinational corporations have come together in the G8 Climate Change Roundtable, a business group formed at the January 2005 World Economic Forum. The group includes Ford, Toyota, British Airways and BP. On 9 June 2005 the Group published a statement[188] stating that there was a need to act on climate change and claiming that market-based solutions can help. It called on governments to establish "clear, transparent, and consistent price signals" through "creation of a long-term policy framework" that would include all major producers of greenhouse gases.





Implementation requires funding sources but is often beset by disputes over who should provide funds and under what conditions.[189] A lack of funding can be a barrier to successful strategies as there are no formal arrangements to finance climate change development and implementation.[190] Funding is often provided by nations, groups of nations and increasingly NGO and private sources. These funds are often channelled through the Global Environmental Facility (GEF). This is an environmental funding mechanism in the World Bank which is designed to deal with global environmental issues.[189] The GEF was originally designed to tackle four main areas: biological diversity, climate change, international waters and ozone layer depletion, to which land degradation and persistent organic pollutant were added. The GEF funds projects that are agreed to achieve global environmental benefits that are endorsed by governments and screened by one of the GEF’s implementing agencies.[191]



Martin Wolfe argued in the Financial Times in 2013 that, in order for effective climate change mitigation to take place, substantial resources needed to be invested in technologies that would deliver a prosperous low-carbon economy. Neither the technology nor the institutions required to deliver it existed in 2013, and hence there was no political will to make effective action.[192]


Despite a perceived lack of occurrence, evidence of implementation is emerging internationally. Some examples of this are the initiation of NAPA’s and of joint implementation. Many developing nations have made National Adaptation Programs of Action (NAPAs) which are frameworks to prioritize adaption needs.[193] The implementation of many of these is supported by GEF agencies.[194] Many developed countries are implementing ‘first generation’ institutional adaption plans particularly at the state and local government scale.[193] There has also been a push towards joint implementation between countries by the UNFCC as this has been suggested as a cost-effective way for objectives to be achieved.[195]

Territorial policies

United States

Efforts to reduce greenhouse gas emissions by the United States include energy policies which encourage efficiency through programs like Energy Star, Commercial Building Integration, and the Industrial Technologies Program.[196] On 12 November 1998, Vice President Al Gore symbolically signed the Kyoto Protocol, but he indicated participation by the developing nations was necessary prior its being submitted for ratification by the United States Senate.[197]

In 2007, Transportation Secretary Mary Peters, with White House approval, urged governors and dozens of members of the House of Representatives to block California’s first-in-the-nation limits on greenhouse gases from cars and trucks, according to e-mails obtained by Congress.[198] The U.S. Climate Change Science Program is a group of about twenty federal agencies and US Cabinet Departments, all working together to address global warming.

The Bush administration pressured American scientists to suppress discussion of global warming, according to the testimony of the Union of Concerned Scientists to the Oversight and Government Reform Committee of the U.S. House of Representatives.[199][200] "High-quality science" was "struggling to get out," as the Bush administration pressured scientists to tailor their writings on global warming to fit the Bush administration's skepticism, in some cases at the behest of an ex-oil industry lobbyist. "Nearly half of all respondents perceived or personally experienced pressure to eliminate the words 'climate change,' 'global warming' or other similar terms from a variety of communications." Similarly, according to the testimony of senior officers of the Government Accountability Project, the White House attempted to bury the report "National Assessment of the Potential Consequences of Climate Variability and Change," produced by U.S. scientists pursuant to U.S. law.[201] Some U.S. scientists resigned their jobs rather than give in to White House pressure to underreport global warming.[199]


Developing countries

In order to reconcile economic development with mitigating carbon emissions, developing countries need particular support, both financial and technical. One of the means of achieving this is the Kyoto Protocol's Clean Development Mechanism (CDM). The World Bank's Prototype Carbon Fund[203] is a public private partnership that operates within the CDM.

An important point of contention, however, is how overseas development assistance not directly related to climate change mitigation is affected by funds provided to climate change mitigation.[204] One of the outcomes of the UNFCC Copenhagen Climate Conference was the Copenhagen Accord, in which developed countries promised to provide US $30 million between 2010 and 2012 of new and additional resources.[204] Yet it remains unclear what exactly the definition of additional is and the European Commission has requested its member states to define what they understand to be additional, and researchers at the Overseas Development Institute have found 4 main understandings:[204]

  1. Climate finance classified as aid, but additional to (over and above) the ‘0.7%’ ODA target;
  4. Increase in climate finance not connected to ODA.


However, none of these initiatives suggest a quantitative cap on the emissions from developing countries. This is considered as a particularly difficult policy proposal as the economic growth of developing countries are proportionally reflected in the growth of greenhouse emissions. Critics of mitigation often argue that, the developing countries' drive to attain a comparable living standard to the developed countries would doom the attempt at mitigation of global warming. Critics also argue that holding down emissions would shift the human cost of global warming from a general one to one that was borne most heavily by the poorest populations on the planet.


Non-governmental approaches


Choices in personal actions and business operations



Air travel and shipment

In 2008, climate scientist Kevin Anderson raised concern about the growing effect of rapidly increasing global air transport on the climate in a paper,[207] and a presentation,[208] suggesting that reversing this trend is necessary to reduce emissions.


Business opportunities and risks



Legal action

In some countries, those affected by climate change may be able to sue major producers. Attempts at litigation have been initiated by entire peoples such as Palau[212] and the Inuit[213], as well as non-governmental organizations such as the Sierra Club.[214] Although proving that particular weather events are due specifically to global warming may never be possible,[215] methodologies have been developed to show the increased risk of such events caused by global warming.[216]


Legal action has also been taken to try to force the U.S. Environmental Protection Agency to regulate greenhouse gas emissions under the Clean Air Act,[220] and against the Export-Import Bank and OPIC for failing to assess environmental impacts (including global warming impacts) under NEPA.

According to a 2004 study commissioned by Friends of the Earth, ExxonMobil and its predecessors caused 4.7 to 5.3 percent of the world's man-made carbon dioxide emissions between 1882 and 2002. The group suggested that such studies could form the basis for eventual legal action.[221]

See also

Global warming portal
Energy portal

By country



  • (pb: 978-0-521-70597-4).
  • (pb: 978-0-521-70598-1).
  • .
  • . Survey website: Ipsos MORI: Poll: Strong global opposition towards nuclear power
  • , RS Policy document 10/09. Report website.

External links

  • Intergovernmental Panel on Climate Change – Includes the Working Group III Report "Mitigation of Climate Change" as part of the Fourth Assessment Report
  • Veerabhadran Ramanathan and Jessica Seddon Wallack.
  • Charles F. Kennel, Veerabhadran Ramanathan.

European Union

  • European Climate Change Programme
  • EU New Energy Policy
  • European Union Greenhouse Gas Emission Trading Scheme (EU ETS)
  • Community strategy to reduce CO2 from light vehicles.
  • UK's Climate Change Programme
  • The Stern Review on the economics of climate change – Parts III and IV of the Stern Review are on climate change mitigation


  • EPA: What You Can Do.
  • U.S. Mayors Climate Protection Agreement signed by 178 mayors representing nearly 40 million Americans
  • California Climate Change Portal.


  • Rivington M, Matthews KB, Buchan K and Miller D (2005) Odense, Denmark, 7–8 November 2005.
  • Scientific American April 2010
  • Global Warming Newswire – published scientific studies on global warming
hu:A globális felmelegedés csökkentése

