Influence of soil C, N2O and fuel use on GHG mitigation with no-till adoption

Previous research has demonstrated that soil carbon sequestration through adoption of conservation tillage can be economically profitable depending on the value of a carbon offset in a greenhouse gas (GHG) emissions market. However adoption of conservation tillage also influences two other potentially important factors, changes in soil N₂O emissions and CO₂ emissions attributed to changes in fuel use. In this article we evaluate the supply of GHG offsets associated with conservation tillage adoption for corn-soy-hay and wheat-pasture systems of the central United States, taking into account not only the amount of carbon sequestration but also the changes in soil N₂O emission and CO₂ emissions from fuel use in tillage operations. The changes in N₂O emissions are derived from a meta-analysis of published studies, and changes in fuel use are based on USDA data. These are used to estimate changes in global warming potential (GWP) associated with adoption of no-till practices, and the changes in GWP are then used in an economic analysis of the potential supply of GHG offsets from the region. Simulation results demonstrate that taking N₂O emissions into account could result in substantial underestimation of the potential for GHG mitigation in the central U.S. wheat pasture systems, and large over-estimation in the corn-soy-hay systems. Fuel use also has quantitatively important effects, although generally smaller than N₂O. These findings suggest that it is important to incorporate these two effects in estimates of GHG offset potential from agricultural lands, as well as in the design of GHG offset contracts for more complete accounting of the effect that no-till adoption will have on greenhouse gas emissions.     

Biological carbon sequestration and carbon trading re-visited

Biological activities that sequester carbon create CO₂ offset credits that could obviate the need for reductions in fossil fuel use. Credits are earned by storing carbon in terrestrial ecosystems and wood products, although CO₂ emissions are also mitigated by delaying deforestation, which accounts for one-quarter of anthropogenic CO₂ emissions. However, non-permanent carbon offsets from biological activities are difficult to compare with each other and with emissions reduction because they differ in how long they prevent CO₂ from entering the atmosphere. This is the duration problem. It results in uncertainty and makes it hard to determine the legitimacy of biological activities in mitigating climate change. Measuring, verifying and monitoring the carbon sequestered in sinks greatly increases transaction costs and leads to rent seeking by sellers of dubious sink credits. While biological sink activities undoubtedly help mitigate climate change and should not be neglected, it is shown that there are limits to the substitutability between temporary offset credits from these activities and emissions reduction, and that this has implications for carbon trading. A possible solution to inherent incommensurability between temporary and permanent credits is also suggested.     

National GHG emissions reduction pledges and 2°C: comparison of studies

This article provides further detail on expected global GHG emission levels in 2020, based on the Emissions Gap Report (United Nations Environment Programme, December 2010), assuming the emission reduction proposals in the Copenhagen Accord and Cancun Agreements are met. Large differences are found in the results of individual groups owing to uncertainties in current and projected emission estimates and in the interpretation of the reduction proposals. Regardless of these uncertainties, the pledges for 2020 are expected to deliver emission levels above those that are consistent with a 2°C limit. This emissions gap could be narrowed through implementing the more stringent conditional pledges, minimizing the use of ‘lenient’ credits from forests and surplus emission units, avoiding double-counting of offsets and implementing measures beyond current pledges. Conversely, emission reduction gains from countries moving from their low to high ambition pledges could be more than offset by the use of ‘lenient’ land use, land-use change and forestry (LULUCF) credits and surplus emissions units, if these were used to the maximum. Laying the groundwork for faster emission reduction rates after 2020 appears to be crucial in any case.     

Combining cap-and-trade with offsets: lessons from the EU-ETS

Linking a cap-and-trade with an offset mechanism has many theoretical advantages: it reduces compliance costs, extends the price signal outside the cap-and-trade, and triggers technology transfer. However, it is feared that such linking will induce outsourcing of emissions reduction at a low price and undermine the price incentive in the cap-and-trade. The EU Emissions Trading Scheme (EU ETS) is the first full-scale example of a cap-and-trade system linked to project-based mechanisms such that offsets have effectively been used by industrial installations. This article is an ex post analysis of EU ETS data for the years 2008 and 2009, and the characteristics of the link and its efficiency are evaluated. Although offsets have been much used, their use is concentrated and not very intense or frequent, which allays the fear that offsets will flood the market. Although the majority of surrendered CERs effectively come from the largest and oldest projects, the credits surrendered are similar to those available on the market. Possible factors that contribute towards inefficiency are the rules for using offsets, transaction costs affecting the participation of small installations, awareness and openness to market-based instruments, and uncertainties regarding CERs offer and demand from other markets. However, the impact on EUA equilibrium price still needs to be quantified.     

On the importance of baseline setting in carbon offsets markets

Incorporating carbon offsets in the design of cap-and-trade programs remains a controversial issue because of its potential unintended impacts on emissions. At the heart of this discussion is the issue of crediting of emissions reductions. Projects can be correctly, over- or under-credited for their actual emissions reductions. We develop a unified framework that considers the supply of offsets within a cap-and-trade program that allows us to compare the relative impact of over-credited offsets and under-credited emissions reductions on overall emissions under different levels of baseline stringency and carbon prices. In the context of a national carbon pricing scheme that includes offsets, we find that the emissions impacts of over-credited offsets can be fully balanced out by under-credited emissions reductions without sacrificing a significant portion of the overall supply of offsets, provided emissions baselines are stringent enough. In the presence of high predicted business-as-usual (BAU) emissions uncertainty or low carbon prices, to maintain the environmental integrity of the program, baselines need to be set at stringent levels, in some cases below 50 percent of predicted BAU emissions. As predicted BAU emissions uncertainty declines or as the carbon market achieves higher equilibrium prices, however, less stringent baselines can balance out the emissions impacts of over-credited offsets and under-credited emissions reductions. These results imply that to maintain environmental integrity of offsets programs, baseline stringency should be tailored to project characteristics and market conditions that influence the proportion of over-credited offsets to under-credited emissions reductions.     

Estimated supply of RED credits 2011–2035

Previous attempts to estimate the supply of greenhouse gas emission reductions from reduced emissions from deforestation (RED) have generally failed to incorporate policy developments, country-specific abilities and political willingness to supply offsets for developed countries’ emissions. To address this, we estimate policy-appropriate projections of creditable emission reductions from RED. Two global forest carbon models are used to examine major assumptions affecting the generation of credits. The results show that the estimated feasible supply of RED credits is significantly below the biophysical mitigation potential from deforestation. A literature review identified an annual RED emission reduction potential between 1.6 and 4.3 Gt CO₂e. Feasible RED supply estimates applying the OSIRIS model were 1.74 Gt CO₂e annually between 2011 and 2020, with a cumulative supply of 17.4 Gt CO₂e under an ‘own-efforts’ scenario. Estimates from the Forest Carbon Index were very low at $5/t CO₂e with 8 million tonne CO₂e annually, rising to 1.8 Gt CO₂e at $20/t CO₂e. Cumulative abatement between 2011 and 2020 was 9 billion Gt CO₂e ($20/t CO₂e). These volumes were lower, sometimes dramatically, at prices of $5/t CO₂e suggesting a non-linear supply of credits in relation to price at a low payment level. For policy makers, the results suggest that inclusion of RED in a climate framework increases abatement potential, although significant constraints are imposed by political and technical issues.     

Controlling GHG emissions from the transportation sector through an ETS: institutional arrangements in Shenzhen,China

Many different approaches are needed to achieve reductions in GHG emissions from the transportation sector. Carbon emissions trading schemes (ETSs) are widely used in industry and are effective in reducing the overall social cost of emissions abatement. This article reports the development of a downstream ETS for the transportation sector and its application in Shenzhen, China. The ETS was devised as a mandatory cap-and-trade scheme and, as a first step, was applied to public transportation. An integrated cap was set on the total emissions from buses and taxis: an absolute cap for existing vehicles and a relative increment for new entrants. Allowances were allocated by grandfathering or benchmarking and a ‘reverse mechanism’ was established to encourage the transformation of urban transportation to a low-carbon system. Online fuel consumption monitoring was used to quantify the emissions from vehicles, and the operators were required to surrender enough allowances or credits to account for their verified annual emissions. The mechanisms for allowance trading and carbon offsets provided sufficient flexibility to make emissions abatement and the use of new-energy vehicles and environmentally friendly travel within Shenzhen's urban transportation system economically attractive.

Policy relevance

The transportation sector is becoming a major contributor to the growth in China's GHG emissions. Achieving large reductions in GHG emissions from the transportation sector is a great challenge and requires both technology and policy innovation. The tradable carbon permit is a popular concept in mitigating climate change, but the introduction of a cap-and-trade ETS into the transportation sector is a relatively innovative concept. Shenzhen has launched the first cap-and-trade ETS in a developing country and is currently exploring ways to mitigate carbon emissions by a downstream cap-and-trade ETS for the transportation sector. This article considers the main institutional arrangements and regulatory framework of Shenzhen's transportation carbon ETS. It not only refreshes the theoretical analysis and practical application of downstream cap-and-trade carbon emissions trading in urban transportation, but also provides developing countries with a cost-effective instrument to mitigate their rapid growth in traffic carbon emissions during urbanization.     

Book review

In 2007 the US Congress began considering a set of bills to implement a cap-and-trade system to limit the nation's greenhouse gas (GHG) emissions. The MIT Integrated Global System Model (IGSM)—and its economic component, the Emissions Prediction and Policy Analysis (EPPA) model—were used to assess these proposals. In the absence of policy, the EPPA model projects a doubling of US greenhouse gas emissions by 2050. Global emissions, driven by growth in developing countries, are projected to increase even more. Unrestrained, these emissions would lead to an increase in global CO₂ concentration from a current level of 380 ppmv to about 550 ppmv by 2050 and to near 900 ppmv by 2100, resulting in a year 2100 global temperature 3.5–4.5°C above the current level. The more ambitious of the Congressional proposals could limit this increase to around 2°C, but only if other nations, including developing countries, also strongly controlled greenhouse gas emissions. With these more aggressive reductions, the economic cost measured in terms of changes in total welfare in the United States could range from 1.5% to almost 2% by the 2040–2050 period, with 2015 CO₂-equivalent prices between $30 and $55, rising to between $120 and $210 by 2050. This level of cost would not seriously affect US GDP growth but would imply large-scale changes in its energy system.     

Sectoral targets for developing countries: combining ‘common but differentiated re-sponsibilities’ with ‘meaningful participation’

Although a global cap-and-trade system is seen by many researchers as the most cost-efficient solution to reduce greenhouse gas (GHG) emissions, the governments of developing countries refuse to enter into such a system in the short term. Many scholars and stakeholders, including the European Commission, have thus proposed various types of commitments for developing countries that appear less stringent, such as sectoral approaches. A macroeconomic assessment of such a sectoral approach is provided for developing countries. Two policy scenarios in particular are assessed, in which developed countries continue with Kyoto-type absolute commitments, while developing countries adopt an emissions trading system limited to electricity generation and linked to developed countries' cap-and-trade systems. In the first scenario, CO₂ allowances are auctioned by the government, which distributes its revenues as a lump sum to households. In a second scenario, the auction revenues are used to reduce taxes on, or to give subsidies to, electricity generation. The quantitative analysis, conducted with a hybrid general equilibrium model, shows that such options provide almost as much emissions reduction as a global cap-and-trade system. Moreover, in the second sectoral scenario, GDP losses in developing countries are much lower than with a global cap-and-trade system, as is also the effect on the electricity price.     

Comparative assessment of Japan's long-term carbon budget under different effort-sharing principles

This article assesses Japan's carbon budgets up to 2100 in the global efforts to achieve the 2?°C target under different effort-sharing approaches based on long-term GHG mitigation scenarios published in 13 studies. The article also presents exemplary emission trajectories for Japan to stay within the calculated budget.

The literature data allow for an in-depth analysis of four effort-sharing categories. For a 450?ppm CO₂e stabilization level, the remaining carbon budgets for 2014–2100 were negative for the effort-sharing category that emphasizes historical responsibility and capability. For the other three, including the reference ‘Cost-effectiveness’ category, which showed the highest budget range among all categories, the calculated remaining budgets (20th and 80th percentile ranges) would run out in 21–29 years if the current emission levels were to continue. A 550?ppm CO₂e stabilization level increases the budgets by 6–17 years-equivalent of the current emissions, depending on the effort-sharing category. Exemplary emissions trajectories staying within the calculated budgets were also analysed for ‘Equality’, ‘Staged’ and ‘Cost-effectiveness’ categories. For a 450?ppm CO₂e stabilization level, Japan's GHG emissions would need to phase out sometime between 2045 and 2080, and the emission reductions in 2030 would be at least 16–29% below 1990 levels even for the most lenient ‘Cost-effectiveness’ category, and 29–36% for the ‘Equality’ category. The start year for accelerated emissions reductions and the emissions convergence level in the long term have major impact on the emissions reduction rates that need to be achieved, particularly in the case of smaller budgets.

Policy relevance

In previous climate mitigation target formulation processes for 2020 and 2030 in Japan, neither equity principles nor long-term management of cumulative GHG emissions was at the centre of discussion. This article quantitatively assesses how much more GHGs Japan can emit by 2100 to achieve the 2?°C target in light of different effort-sharing approaches, and how Japan's GHG emissions can be managed up to 2100. The long-term implications of recent energy policy developments following the Fukushima nuclear disaster for the calculated carbon budgets are also discussed.     

Carbon accounting for sinks in the CDM after CoP-9

Abstract

The role of sinks in the clean development mechanism (CDM) has been a subject of controversy for several reasons; one being that temporary carbon storage in forests appeared to prevent any opportunity to use them as an option to reduce permanent greenhouse gas (GHG) emissions. In Milan (December 2003), the Conference of the Parties (CoP) decided to address this problem by introducing two types of expiring units: temporary CERs (tCERs) and long-term CERs (lCERs). Countries committed to emission reductions may acquire these units to temporarily offset their emissions and thus to postpone permanent emission reductions. As further decided by the CoP, baseline emissions of GHGs and the enhancement of sinks outside the project boundary will not be accounted for in the calculation of tCERs or lCERs. The contribution of CDM-sink projects to GHG emissions abatement will therefore be greater than what will be credited to them. On the other hand, permanent GHG emissions that may result as a consequence of the implementation of sink project activities are treated as non-permanent. If these emissions are above avoided baseline emissions, CDM-sinks will result in net increases of GHG emissions into the atmosphere. After briefly reassessing the non-permanence problem, this article explains how tCERs and lCERs should be quantified according to Decision 19/CP.9 of CoP-9 and how calculations are implemented in the forthcoming software CO₂ Land. Using a simple numerical example, it illustrates how the GHG accounting rule adopted at CoP-9 may result in net increases of GHG emissions. In the conclusion, a possible solution to this problem is proposed.     

Corrigendum to: Incremental CH4 and N2O mitigation benefits consistent with the U.S. Government's SC-CO2 estimates

The light bulb ban introduced by the EU is used as an example to illustrate how to assess the climate impact of a policy that overlaps with a cap-and-trade scheme. The European Commission estimates that by 2020 the reduction in GHG emissions induced by banning incandescent light bulbs will reach 15 million tons annually. The number is a conservative estimate for the reduction in emissions from lighting if the total residential stock of incandescent light bulbs in 2008 is replaced by more efficient lighting sources. However, it ignores that use-phase and some non-use-phase emissions are covered by the EU Emission Trading Scheme (EU ETS). This drastically reduces the amount of GHG emissions saved.

Policy relevance

Several policies such as the EU-wide ban on incandescent light bulbs, energy efficiency mandates and support mechanisms for renewable energy overlap with the EU ETS. While there are typically several justifications for these policies, a chief reason is the reduction of GHG emissions. However, given that the aggregate emissions of the industries covered are fixed by the EU ETS, the climate change mitigation aspect of these policies is not obvious. Using the light bulb ban as an example, this article illustrates how a focus on non-EU ETS emissions changes the assessment of an intervention in terms of GHG reductions.     

Greenhouse gas emissions from the usage of typical e-products by households: a case study of China

The number of electric and electronic products (e-products) owned by Chinese households has multiplied in the past decade. In this study, we analyz the GHG emissions from e-products in Chinese households in order to understand and determine how to mitigate their effects on climate change. The results show that the usage stage of e-products has become an important source of GHG emissions in China, with total GHG emissions of these household e-products reaching about 663 million tons CO₂ eq., accounting for about 8.85 % of all Chinese GHG emissions in 2012. The average GHG emission per household per year in China was 1538 kg CO₂ eq. in 2012, a little higher than that of Norwegian households (1200 kg CO₂ eq.). The electricity mix plays a very important role in GHG emissions, and the 78 % coal-fired power consumption accounted for 99.69 % of the total GHG emissions. Our research also supports the view that GHG emissions from household e-products increased with economic level. To reduce the GHG emissions of household e-products, the development of energy-saving e-products and changes to the electricity mix would be very effective measures.     

Carbon taxes,cap-and-trade administration,and US legislation

An upstream cap-and-trade system that rations allowances for the carbon content of fuel inputs could achieve wider coverage than existing CO₂ emission programmes or most of those proposed in draft US legislation, but would risk shortages and price spikes. Allowance price volatility could be avoided with a CO₂-price corridor established through auctions, similar in some respects to how central banks manage short-term interest rates with open market operations. Building on the central bank analogy, a Greenhouse Gas Board could be established with the ‘instrument independence’ to set annual CO₂-price corridors in line with broadly-framed, long-term climate goals laid out in legislation. National and regional Boards of this nature might also help facilitate the international coordination of climate policies.     

Regulatory control of vehicle and power plant emissions: how effective and at what cost?

Passenger vehicles and power plants are major sources of GHG emissions. While economic analyses generally indicate that a broader market-based approach to GHG reduction would be less costly and more effective, regulatory approaches have found greater political success. We evaluate a global regulatory regime that replaces coal with natural gas in the electricity sector and imposes technically achievable improvements in the efficiency of personal transport vehicles. Its performance and cost are compared with other scenarios of future policy development including a no-policy world, achievements under the Copenhagen Accord, and a price-based policy to reduce global emissions by 50% by 2050. The assumed regulations applied globally achieve a global emissions reduction larger than projected for the Copenhagen agreements, but they do not prevent global GHG emissions from continuing to grow. The reduction in emissions is achieved at a high cost compared to a price-based policy. Diagnosis of the reasons for the limited yet high-cost performance reveals influences including the partial coverage of emitting sectors, small or no influence on the demand for emissions-intensive products, leakage when a reduction in fossil use in the covered sectors lowers the price to others, and the partial coverage of GHGs. If these regulatory measures are in part correcting other barriers or behavioural limitations consumers face, the benefits of overcoming these could offset at least some of the costs we estimate. The extent of any efficiency gap – the difference between engineering estimates of best practice and what actually happens – is highly contested, and offers an important avenue for future research.

Policy relevance

While analysts concerned with national cost of GHG control have long advocated a GHG pricing policy, by a cap-and-trade system or a tax, covering all emissions sources and gases, governments more often pursue sectoral policies and technology standards. Given these political realities, the regulations represent a more politically practical approach to GHG reductions, focusing on solutions that are within reach and that do not depend on technological breakthroughs. If regulations are imposed as a way to get started on larger emissions reductions, and then combined with a broader GHG pricing policy pursuing a deep global cut in emissions, its requirements will eventually be overtaken by the pricing policy. The remaining higher costs of the regulatory targets become diluted so that in later years the difference in average cost per ton between a least-cost approach and one preceded by a period of regulatory action becomes very small.     

Incremental CH4 and N2O mitigation benefits consistent with the US Government's SC-CO2 estimates

Benefit–cost analysis can serve as an informative input into the policy-making process, but only to the degree it characterizes the major impacts of the regulation under consideration. Recently, the US, amongst other nations, has begun to use estimates of the social cost of CO₂ (SC-CO₂) to develop analyses that more fully capture the climate change impacts of GHG abatement. The SC-CO₂ represents the aggregate willingness to pay to avoid the damages associated with an additional tonne of CO₂ emissions. In comparison, the social costs of non-CO₂ GHGs have received little attention from researchers and policy analysts, despite their non-negligible climate impact. This article addresses this issue by developing a set of social cost estimates for two highly prevalent non-CO₂ GHGs, methane and nitrous oxide. By extending existing integrated assessment models, it is possible to develop a set of social cost estimates for these gases that are consistent with the SC-CO₂ estimates currently in use by the US federal government.Policy relevanceWithin the benefit–cost analyses that inform the design of major regulations, all Federal agencies within the US Government (USG) use a set of agreed upon SC-CO₂ estimates to value the impact of CO₂ emissions changes. However, the value of changes in non-CO₂ GHG emissions has not been included in USG policy analysis to date. This article addresses that omission by developing a set of social cost estimates for two highly prevalent non-CO₂ GHGs, methane and nitrous oxide. These new estimates are designed to be compatible with the USG SC-CO₂ estimates currently in use and may therefore be directly applied to value emissions changes for these non-CO₂ gases within the benefit–cost analyses used to evaluate future policies.     

Biofuels and carbon management

Public policy supports biofuels for their benefits to agricultural economies, energy security and the environment. The environmental rationale is premised on greenhouse gas (GHG, “carbon”) emissions reduction, which is a matter of contention. This issue is challenging to resolve because of critical but difficult-to-verify assumptions in lifecycle analysis (LCA), limits of available data and disputes about system boundaries. Although LCA has been the presumptive basis of climate policy for fuels, careful consideration indicates that it is inappropriate for defining regulations. This paper proposes a method using annual basis carbon (ABC) accounting to track the stocks and flows of carbon and other relevant GHGs throughout fuel supply chains. Such an approach makes fuel and feedstock production facilities the focus of accounting while treating the CO₂ emissions from fuel end-use at face value regardless of the origin of the fuel carbon (bio- or fossil). Integrated into cap-and-trade policy and including provisions for mitigating indirect land-use change impacts, also evaluated on an annual basis, an ABC approach would provide a sound carbon management framework for the transportation fuels sector.     

Sector-based approach to the post-2012 climate change policy architecture

A sectoral approach to GHG emissions reductions in developing countries is proposed as a key component of the post-2012 climate change mitigation framework. In this approach, the ten highest-emitting developing countries in the electricity and other major industrial sectors pledge to meet voluntary, ‘no-lose’ GHG emissions targets in these sectors. No penalties are incurred for failing to meet a target, but emissions reductions achieved beyond the target level earn emissions reduction credits (ERCs) that can be sold to industrialized nations. Participating developing countries establish initial ‘no-lose’ emissions targets, based upon their national circumstances, from sector-specific energyintensity benchmarks that have been developed by independent experts. Industrialized nations then offer incentives for the developing countries to adopt more stringent emissions targets through a ‘Technology Finance and Assistance Package’, which helps to overcome financial and other barriers to technology transfer and deployment. These sectorspecific energy-intensity benchmarks could also serve as a means for establishing national economy-wide targets in developed countries in the post-2012 regime. Preliminary modelling of a hybrid scenario, in which Annex I countries adopt economy-wide absolute GHG emissions targets and high-emitting developing countries adopt ‘no-lose’ sectoral targets, indicates that such an approach significantly improves the likelihood that atmospheric concentrations of CO₂ can be stabilized at 450 ppmv by the end of the century.     

Russia at GHG Market

In the first Kyoto commitment period Russia could be the major supplier for the greenhouse gases (GHG) emissions market. Potential Russian supply depends on the ability of Russia to keep GHG emissions lower than the Kyoto target. In the literature there is no common understanding of the total trading potential of Russia at the international carbon market. In this paper we focus on CO₂ emission, which constituted nearly 80%of Russian GHG emission. We compare different projections of Russian CO₂emission and analyze the most important factors, which predetermine the CO₂emission growth. In a transition economy these factors are: Gross Domestic Product(GDP) dynamic, changes of GDP structure, innovation activity, transformation of export-import flows and response to the market signals. The input-output macroeconomic model with the two different input-output tables representing old and new production technologies has been applied for the analysis to simulate technological innovations and structural changes in the Russian economy during transition period. The Russian supply at the international GHG market without forest sector may be up to 3 billion metric ton of CO₂ equivalent. Earlier actions to reduce CO₂ emission are critical to insure theRussiansupply at the international carbon market. With regard to the current status of the Russian capital market, the forward trading with OECD countries is only the possibility to raise initial investments to roll no-regret and low-cost GHG reduction. This paper discusses uncertainties of RussianCO₂emission dynamics and analyzes the different incentives to lower the emission pathway.     

The danger of overvaluing methane’s influence on future climate change

Minimizing the future impacts of climate change requires reducing the greenhouse gas (GHG) load in the atmosphere. Anthropogenic emissions include many types of GHG’s as well as particulates such as black carbon and sulfate aerosols, each of which has a different effect on the atmosphere, and a different atmospheric lifetime. Several recent studies have advocated for the importance of short timescales when comparing the climate impact of different climate pollutants, placing a high relative value on short-lived pollutants, such as methane (CH₄) and black carbon (BC) versus carbon dioxide (CO₂). These studies have generated confusion over how to value changes in temperature that occur over short versus long timescales. We show the temperature changes that result from exchanging CO₂ for CH₄ using a variety of commonly suggested metrics to illustrate the trade-offs involved in potential carbon trading mechanisms that place a high value on CH₄ emissions. Reducing CH₄ emissions today would lead to a climate cooling of approximately ~0.5 °C, but this value will not change greatly if we delay reducing CH₄ emissions by years or decades. This is not true for CO₂, for which the climate is influenced by cumulative emissions. Any delay in reducing CO₂ emissions is likely to lead to higher cumulative emissions, and more warming. The exact warming resulting from this delay depends on the trajectory of future CO₂ emissions but using one business-as usual-projection we estimate an increase of 3/4 °C for every 15-year delay in CO₂ mitigation. Overvaluing the influence of CH₄ emissions on climate could easily result in our “locking” the earth into a warmer temperature trajectory, one that is temporarily masked by the short-term cooling effects of the CH₄ reductions, but then persists for many generations.