Seeing the trees for the carbon: agroforestry for development and carbon mitigation

Land-use, land-use change and forestry (LULUCF) activities will play an important role in global climate change mitigation. Many carbon schemes require the delivery of both climate and rural development benefits by mitigation activities conducted in developing countries. Agroforestry is a LULUCF activity that is gaining attention because of its potential to deliver climate benefits as well as rural development benefits to smallholders. There is hope that agroforestry can deliver co-benefits for climate and development; however experience with early projects suggests co-benefits are difficult to achieve in practice. We review the literature on agroforestry, participatory rural development, tree-based carbon projects and co-benefit carbon projects to look at how recommended project characteristics align when trying to generate different types of benefits. We conclude that there is considerable tension inherent in designing co-benefit smallholder agroforestry projects. We suggest that designing projects to seek ancillary benefits rather than co-benefits may help to reduce this tension.     

Characteristics of forest carbon credit transactions in the voluntary carbon market

The voluntary carbon market allows participants to go beyond regulatory carbon offsetting. Recent developments have improved the transparency and credibility of voluntary carbon trading, and forest carbon credit transactions constitute more than half of trade volume. Its workings, however, have not been sufficiently explored in the literature. This study analyses the characteristics of forest carbon credit transactions in the voluntary carbon market using frequency analysis and logistic regression analysis. The results reveal that the co-benefits of forest carbon projects are an important factor influencing carbon credit transactions. From the higher transaction ratio of credits from CCB Standards-labelled projects and projects using co-benefit-oriented standards, it can be inferred that credits with potential for co-benefits (e.g. fostered corporate social responsibility, social cohesion of local communities and voluntary leadership, and positive environmental impacts) are preferred to those focusing exclusively on emission reduction in the voluntary carbon market. The findings of this study suggest that developing co-benefits is important for strengthening the market competitiveness of forest carbon credits in the voluntary carbon market. Additionally, unlike the compliance carbon market, in the voluntary carbon market stringent carbon standards do not always guarantee credit transaction performance.

POLICY RELEVANCE

After UNFCCC COP-21, the global society agreed to acknowledge various forms of international carbon crediting mechanisms, and noted the significance of greenhouse gas emissions reduction for sustainable development and environmental integrity through the Paris Agreement. Moreover, the agreement encouraged both REDD+ activities in developing countries and supports from developed countries. Additionally, co-benefits of forest carbon projects are important for credit transaction in the global voluntary carbon market. Under the new climate regime, co-benefits of forest carbon projects are expected to gain attention in the carbon market. To promote the social, economic, and environmental co-benefits of forest carbon projects, the introduction of an objective co-benefit assessment and certification system should be reviewed at the national level.     

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.     

Delayed carbon sequestration and rising carbon prices

We set out a dynamic model to investigate optimal time paths of emissions, carbon stocks and carbon sequestration by land conversion, allowing for non-instantaneous carbon sequestration. Previous research in a dynamic general equilibrium framework, assuming instantaneous carbon sequestration, has shown that land conversion should take place as soon as possible. On the contrary, previous research within a partial equilibrium framework has shown that, with increasing carbon prices, it is optimal to delay carbon sequestration through land conversion. We show that land use change alternatives, e.g. reforestation, have to be used as soon as possible before the singular path is reached, i.e. the unique trajectory that brings the system to the steady-state. We also show that faster increasing carbon prices can induce a reduction in the rate of reforestation, and that this may take place after an initial phase of increased reforestations or even immediately, depending upon the shape of the increase in carbon prices. Finally, we show that the type of species used is relevant and that the land conversion rate gets smaller the longer it takes the trees to grow. We analyze four different carbon accounting methods, describing the conditions that make them efficient and discussing the comparative advantages of each of them.     

Ocean-circulation model of the carbon cycle

A three-dimensional model of the natural carbon cycle in the oceans is described. The model is an extension of the inorganic ocean-circulation carbon cycle model of Maier-Reimer and Hasselmann (1987) to include the effect of the ocean biota. It is based on a dynamic, general circulation model of the world oceans. Chemical species important to the carbon cycle are advected by the current field of the general circulation model. Mixing occurs through numerical diffusivity (related to finite box size), a small explicit horizontal diffusivity, and a convective adjustment. An atmospheric box exchanges CO₂ with the surface ocean. There is no land biota provided in the present version of the model. The effect of the ocean biota on ocean chemistry is represented in a simple way and model distributions of chemical species are compared with distributions observed during the GEOSECS and other expeditions. Offprint requests to: R Bacastow     

Factors influencing anthropogenic carbon dioxide uptake in the North Atlantic in models of the ocean carbon cycle

The uptake and storage of anthropogenic carbon in the North Atlantic is investigated using different configurations of ocean general circulation/carbon cycle models. We investigate how different representations of the ocean physics in the models, which represent the range of models currently in use, affect the evolution of CO₂ uptake in the North Atlantic. The buffer effect of the ocean carbon system would be expected to reduce ocean CO₂ uptake as the ocean absorbs increasing amounts of CO₂. We find that the strength of the buffer effect is very dependent on the model ocean state, as it affects both the magnitude and timing of the changes in uptake. The timescale over which uptake of CO₂ in the North Atlantic drops to below preindustrial levels is particularly sensitive to the ocean state which sets the degree of buffering; it is less sensitive to the choice of atmospheric CO₂ forcing scenario. Neglecting physical climate change effects, North Atlantic CO₂ uptake drops below preindustrial levels between 50 and 300 years after stabilisation of atmospheric CO₂ in different model configurations. Storage of anthropogenic carbon in the North Atlantic varies much less among the different model configurations, as differences in ocean transport of dissolved inorganic carbon and uptake of CO₂ compensate each other. This supports the idea that measured inventories of anthropogenic carbon in the real ocean cannot be used to constrain the surface uptake. Including physical climate change effects reduces anthropogenic CO₂ uptake and storage in the North Atlantic further, due to the combined effects of surface warming, increased freshwater input, and a slowdown of the meridional overturning circulation. The timescale over which North Atlantic CO₂ uptake drops to below preindustrial levels is reduced by about one-third, leading to an estimate of this timescale for the real world of about 50 years after the stabilisation of atmospheric CO₂. In the climate change experiment, a shallowing of the mixed layer depths in the North Atlantic results in a significant reduction in primary production, reducing the potential role for biology in drawing down anthropogenic CO₂.     

Considering the influence of sequestration duration and carbon saturation on estimates of soil carbon capacity

Rates of soil C sequestration have previously been estimated for a number of different land management activities, and these estimates continue to improve as more data become available. The time over which active sequestration occurs may be referred to as the sequestration duration. Integrating soil C sequestration rates with durations provides estimates of potential change in soil C capacity and more accurate estimates of the potential to sequester C. In agronomic systems, changing from conventional plow tillage to no-till can increase soil C by an estimated 16±3%, whereas increasing rotation intensity can increase soil C by an estimated 6±3%. The increase in soil C following a change in rotation intensity, however, may occur over a slightly longer period (26 yr) than that for tillage cessation (21 yr). Sequestration strategies for grasslands have, on average, longer sequestration durations (33 yr) than for croplands. Estimates for sequestration rates and durations are mean values and can differ greatly between individual sites and management practices. As the annual sequestration rate declines over the sequestration duration period, soil C approaches a new steady state. Sequestration duration is synonymous with the time to which soil C steady state is reached. However, soils could potentially sequester additional C following additional changes in management until the maximum soil C capacity, or soil C saturation, is achieved. Carbon saturation of the soil mineral fraction is not well understood, nor is it readily evident. We provide evidence of soil C saturation and we discuss how the steady state C level and the level of soil C saturation together influence the rate and duration of C sequestration associated with changes in land management.     

Reproduction and the carbon legacies of individuals

Much attention has been paid to the ways that people’s home energy use, travel, food choices and other routine activities affect their emissions of carbon dioxide and, ultimately, their contributions to global warming. However, the reproductive choices of an individual are rarely incorporated into calculations of his personal impact on the environment. Here we estimate the extra emissions of fossil carbon dioxide that an average individual causes when he or she chooses to have children. The summed emissions of a person’s descendants, weighted by their relatedness to him, may far exceed the lifetime emissions produced by the original parent. Under current conditions in the United States, for example, each child adds about 9441 metric tons of carbon dioxide to the carbon legacy of an average female, which is 5.7 times her lifetime emissions. A person’s reproductive choices must be considered along with his day-to-day activities when assessing his ultimate impact on the global environment.     

Improving the scientific assessment of carbon sinks

Abstract

The future role of carbon sinks with reference to the Kyoto Protocol depends significantly on developing an international consensus on carbon-sink assessment and carbon accounting. A clear and practical approach is needed that allows both the scientific community and policy-makers to construct a viable operational framework. This article proposes that a new strategy be developed for carbon-sink assessment based on full carbon accounting (FCA) alongside a separate political tool for carbon accounting. This approach is derived from the experience of the European critical loads (CL) concept, which seeks to quantify levels of pollutants (such as sulfur) that can be absorbed by the environment without causing ecological harm. Crucial to the implementation of such a strategy are robust institutional settings, such as an internationally coordinated monitoring system, open and fair access to the assessment processes, and international research cooperation programs for addressing associated problems of carbon-sink activities.     

Why the CDM will reduce carbon leakage

Carbon leakage is an important concern because it can reduce the environmental effectiveness of the Kyoto Protocol. The Clean Development Mechanism (CDM), one of the flexibility mechanisms allowed under the protocol, has the potential to reduce carbon leakage significantly because it reduces the relative competitive disadvantage to Annex-B countries of restricting greenhouse gas emissions. The economic rationale behind this mechanism is explored in a theoretical analysis. It is then analysed numerically using a computable general equilibrium (CGE) model. The results indicate that, assuming appropriate accounting for leakage and under realistic assumptions on CDM activity, the CDM has the potential to reduce the magnitude of carbon leakage by more than one-half.     

Skills constraints and the low carbon transition

Achieving a successful transition to a low carbon economy, in the UK and other countries, will require sufficient people with appropriate qualifications and skills to manufacture, install, and operate the low carbon technologies and approaches. The actual numbers and types of skills required are uncertain and will depend on the speed and direction of the transition pathways, but there are reasons to doubt that market mechanisms will deliver the necessary skilled workers in a timely manner. The range of market, government, and governance failures relating to the provision of low carbon skills are examined, particularly for their potential to cause a slower, costlier, and less employment-intensive transition. The potential policy responses to these failures are considered, including standardization of funding for training; formalization of transferable qualifications; legally binding targets for carbon emissions reductions and low carbon technology deployment; framework contracts and agreements between actors in key sectors; licensing and accreditation schemes for key technology sectors; government support for skills academies and training centres; support for first movers in niches; increasing mobility of workers; and providing a clear long-term cross-sectoral framework for a low carbon transition, including skills training.

Policy relevance

The article argues for the importance of skills issues for a successful transition to a low carbon economy. It outlines the potential causes of skills shortages, both generic and those specific to low carbon, as well as the probable impact of these types of shortages. By changing existing sectoral and occupational patterns, the transition will disrupt the existing market and government mechanisms to identify and remedy skills shortages in specific sectors. The nature and required pace of the low carbon transition also means that there are pressures that could induce greater skills shortages. These shortages, in turn, could critically delay elements of the transition and increase its cost and duration. The article outlines approaches taken to address these causes of skills shortages, drawing on examples from UK low carbon policy. The article ends with an argument that skills issues need to be more central to transitions debates.     

Leviathan carbon taxes in the short run

A cap is imposed on the carbon tax rate if the total tax revenue is not allowed to increase. Using recent data on the carbon-intensity of the economy and the overall tax take, I show that this cap constrains almost any climate policy in at least some countries. A larger number of countries, emitting a substantial share of global carbon dioxide, cannot fully participate if the carbon tax (or equivalent alternative regulation) is high enough to meet the 2?°C target. For that target, the carbon tax revenue in 2020 is greater than 10?% of total tax revenue in every country.     

Linking the CDM with domestic carbon markets

Certified emission reductions (CERs) from Clean Development Mechanism (CDM) projects have traditionally served as an indirect link between cap and trade systems around the world. However, since 2010, import restrictions have increased. Reasons for import limitations include the supplementarity principle, genuine concerns about the environmental integrity of CERs and social benefits of CDM projects, pressure from domestic emissions mitigation industries, concerns about competition in the industries in which reductions take place, as well as the attempt to pressure advanced developing countries to accept national emissions commitments under a future international climate policy regime. It is shown that import limitations lead to a decrease in CER prices and a race to generate CERs as quickly as possible. Such effects are visible in the CDM market after the EU announced its import limitations. The exclusion of CERs from specific project types will distort the CDM supply curve and increase the CER price unless the marginal abatement costs of the excluded project type are above the CER world market price. Similarly, exclusion of CERs from specific host countries will increase the price. Substantial differences are found in CER access to national carbon markets around the world.Policy relevanceCDM regulators could try to improve access of CERs to cap and trade schemes through improvements to additionality testing, standardizing baseline and monitoring methodologies and stakeholder consultation. However, regulators should be aware that standardization is no panacea, and controversies may resurface if standardized additionality determination (e.g. through benchmarks or positive lists) are applied for a certain period and found to be problematic. However, domestic policy concerns such as an unwillingness to send money abroad to buy credits, an inability to control market prices, and competitiveness impacts cannot be resolved by CDM reforms. If, despite such reforms of the CDM, blatant protectionism continues, a challenge before the World Trade Organisation (WTO) could be launched to stop discrimination of service exports from specific countries.     

Aerosol light absorption, black carbon, and elemental carbon at the Fresno Supersite, California

Particle light absorption (b_ap), black carbon (BC), and elemental carbon (EC) measurements at the Fresno Supersite during the summer of 2005 were compared to examine the equivalency of current techniques, evaluate filter-based b_ap correction methods, and determine the EC mass absorption efficiency (σ_ap) and the spectral dependence of b_ap. The photoacoustic analyzer (PA) was used as a benchmark for in-situ b_ap. Most b_ap measurement techniques were well correlated (r ≥ 0.95). Unadjusted Aethalometer (AE) and Particle Soot Absorption Photometer (PSAP) b_ap were up to seven times higher than PA b_ap at similar wavelengths because of absorption enhancement by backscattering and multiple scattering. Applying published algorithms to correct for these effects reduced the differences to 24 and 17% for the AE and PSAP, respectively, at 532 nm. The Multi-Angle Absorption Photometer (MAAP), which accounts for backscattering effects, overestimated b_ap relative to the PA by 51%. BC concentrations determined by the AE, MAAP, and Sunset Laboratory semi-continuous carbon analyzer were also highly correlated (r ≥ 0.93) but differed by up to 57%. EC measured with the IMPROVE/STN thermal/optical protocols, and the French two-step thermal protocol agreed to within 29%. Absorption efficiencies determined from PA b_ap and EC measured with different analytical protocols averaged 7.9 ± 1.5, 5.4 ± 1.1, and 2.8 ± 0.6 m²/g at 532, 670, and 1047 nm, respectively. The Angström exponent (α) determined from adjusted AE and PA b_ap ranged from 1.19 to 1.46. The largest values of α occurred during the afternoon hours when the organic fraction of total carbon was highest. Significant biases associated with filter-based measurements of b_ap, BC, and EC are method-specific. Correcting for these biases must take into account differences in aerosol concentration, composition, and sources.