What do I mean by infrastructure in this context? I mean those things that enable implementation of policy in all sectors and at all levels. I include in this list:

1. The scientific knowledge necessary to understand the problem and the technologies to address it
2. The legal and regulatory systems to manage the problem
3. In this era of information technology, the information management and decision support systems necessary to address a global problem that is pervasive in its implications
4. The technical standards (i.e., rules, codes, etc.) that facilitate industry and other actors to coordinate and act cost-effectively with high degrees of quality assurance
5. Adequate quantity and quality of human resources to address the problem and educational systems to supply well-training professionals

There is much work yet to be done to develop the legal and regulatory infrastructure necessary to mitigate GHG emissions. However, as we all are aware, further progress on this front awaits an expanded political consensus.

Significant investment is going into new information technology systems designed to manage GHG emissions in anticipation of future policy and emission markets. Yet, the quality of products available varies widely and poorly understood. By offering substantive third-party testing the Institute has begun working to address this opacity.

Globally the body of standards that will need to be developed to support the range of policies, technologies, and markets is still in its infancy. GHG standards to-date are for the most part overly broad and non-specific. The engineering and scientific communities have yet to heavily engage and support the development of more detailed and rigorous standards along the lines of what we see in other industries. Standards development has been systemically hamstrung by the expense and time existing approaches and processes require. However, when you consider the speed and scale at which standards must be developed to keep pace with the demands of a carbon constrained the question of whether existing processes are up to the task emerges. (We will discuss this issue in greater depth in a future blog post detailing the work the GHG Management Institute is undertaking to revolutionize the development of standards, methodologies, protocols, and codes.)

And clearly, the Institute is strongly focused on training and education: building the GHG measurement and management workforce of the future. This has been a key focus since the Institute was founded, and is visible in range of initiatives from our courses to our developing professional certification program, even our workforce survey.

But, in this blog post, I want to focus on the first of these infrastructure components: scientific knowledge. The Institute is not a research organization, so our role here is not to generate new science. But as a convening organization we network GHG professionals from around the world, providing the for a for the emerging discipline of GHG professionals and researchers to develop the intellectual foundation of the field. One of the key ways we are doing this is with the new peer-reviewed scholarly journal we have launched with Earthscan. The journal’s title is Greenhouse Gas Measurement and Management, and it is unique in its focus on the intellectual infrastructure we will need to go beyond just policy debate and design and move onto the serious work of IMPLEMENTATION.

We encourage you to spread the word about this new important journal and to even consider submitting a paper yourself.

The aims and scope of the journal are as follows:

Greenhouse Gas Measurement & Management (GHGMM) is a scholarly peer-reviewed journal that aims to provide reliable and up-to-date research and information on a broad range of issues relating to greenhouse gases (GHGs) to the growing community of professionals dealing with climate change.

As the old saying goes “you cannot manage what you do not measure.” GHGMM covers the application of science, engineering, and economic principles to improve the way society mitigates the anthropogenic causes of global climate change. This includes developing and providing reliable performance metrics related to GHG emissions and removals and managing activities that reduce GHG emissions to and/or increase their removals from the atmosphere.

GHGMM is relevant to a variety of emission and removal accounting frameworks (i.e., system boundaries), each of which define the metrics that support particular mitigation policies and activities, such as those resulting from international treaties, domestic regulations, industrial efforts, or consumer actions. These GHG accounting frameworks (levels) include:

• global;
• national;
• sectoral, program, and policy;
• technology, product, life cycle, and supply-chain;
• entity (e.g., corporate emissions inventory);
• facility (i.e., installation); and
• project (e.g., offsets).

To mitigate GHGs, it is essential to ensure the availability of reliable data regarding their emissions and removals, which is achieved through the design and application of regulatory and compliance-relevant Measurement, Reporting and Verification (MRV) systems. These systems and rules for GHG emission and removal metrics must take into account the context of policy developments and industry practices. Specifically, the measurement of GHGs includes the following issues:

• Metering and sensors – collecting primary data of direct GHG emissions and relevant proxy data with which emissions or removals can be monitored and estimated;
• GHG protocols, standards, methodologies, emission inventories, accounting and metrics – designing, applying, and understanding the limitations of different approaches used for measuring, estimating, reporting and verifying GHG emissions and removals (including issues such as boundaries, additionality, baselines, leakage, and permanence); and using different technologies for various accounting frameworks and sectors (e.g., fuel combustion, agriculture, forestry, waste management, etc.);
• Uncertainty – understanding and managing uncertainty in the measurement and estimation of GHG emissions, removals and storage;
• Quality Assurance/Quality Control (QA/QC) – establishing and enhancing QA/QC and auditing processes, including validation of approaches and verification of GHG emissions, removals and storage;
• Information and communication technologies (ICTs) – developing and using software and other tools for the measurement and estimation of GHG emissions, removals and storage.

Managing GHG emissions involves: the use of performance metrics, systems engineering, and economic analyses to identify mitigation activities, as well as planning, organizing, staffing, directing, and controlling the implementation of these activities. Specifically, the management of GHGs includes the following issues:

• Mitigation analysis – understanding, identifying, assessing and selecting appropriate policies (including economic and market-based instruments), measures, technologies and business strategies that aim to mitigate GHGs;
• Mitigation implementation – understanding the behavioral and technological options for reducing emissions and enhancing removals in a given context and managing the implementation of selected mitigation activities;
• Performance management – accounting for, and measuring, the effectiveness of implemented mitigation activities and technologies at all levels and using metrics to improve performance;
• Emissions analysis – predicting and modeling the effects of specific mitigation activities, products or technologies on GHG emissions and removals;
• Information and communication technologies (ICTs) – developing and using software and other tools for the management of GHGs;
• Adaptation and pollutant emissions – identifying synergies and co-benefits between activities that reduce GHGs, adaptation to the impacts of climate change, and emissions of other pollutants;
• Social issues – understanding the social, economic, and political factors, risks, opportunities, and governance issues relating to the management of GHGs (e.g., corporate disclosure, community right to know).

GHGMM will be open to different types of articles, including:

• Original research papers (for example, on topics relating to: theoretical and practical developments on GHGs, concepts and methods, empirical analysis, policy assessments)
• Short communications/Case studies
• Invited reviews
• Opinion pieces/Commentaries
• Book reviews
• Meeting reports

The first regional workshop on GHG inventories and accounting took place at the 5th Asian Clean Energy Forum (ACEF) hosted by ADB and USAID on June 21, 2010 in ADB’s headquarters in Manila. GHGMI’s Gao Pronove presented at the workshop and shared GHGMI’s experience as the leading training provider for GHG accounting, verification, and management. The ACEF website features all of the presentations, including GHGMI’s.

The workshop was organized by USAID and ADB and recognizes “the critical role that greenhouse gas (GHG) inventories and accounting play in formulating and supporting effective policies for mitigating climate change” and promoting clean energy. The workshop followed two main themes: understanding the roles of different stakeholders, including manufacturers, utilities, civil society, and national, regional, and local governments; and sharing experience with approaches for developing GHG programs (both internationally and within Asia) that build on existing systems where possible and create new systems where needed.

GHGMI was very pleased to share its experience offering certificate training programs in –

• GHG Accounting
• Organizational GHG Management
• GHG Accounting and Verification
• GHG Offset Projects
• Advanced GHG Accounting
• Advanced GHG Offset Projects

GHGMI also shared its experience in developing professional certification standards for individual GHG professionals. The importance of developing a global workforce that is qualified and well-trained was discussed during the workshop.

I would venture to guess that many of you are unaware that most GHG emission inventories and offset project methodologies underestimate actual emissions from fugitive emissions of methane. This is the case because these methodologies systemically forget to include an emissions category: “indirect CO₂ from the atmospheric oxidation of CH₄.”

The fact is that when methane is anthropogenically emitted, methane is oxidized in the atmosphere a decade or two later. Once oxidized, the carbon in each methane molecule is converted to CO₂, which then stays in the atmosphere as CO₂ for another century or more. So really, when methane is emitted, you get a double whammy: first from the methane itself followed by the CO₂ that results from atmospheric oxidization.

Many of you may assume that the GWP of methane would account for this oxidization, right? Wrong! This effect is not included in the GWP of methane, and it should not be included. Why? Simply stated, the effect depends on the origin of the methane. We have to treat methane from biogenic sources (such as livestock and rice paddies) different from fossil sources (such as coal mines and natural gas leaks), as only methane from fossil fuels result in a net addition of CO₂ to the atmosphere following atmospheric oxidation.

Because of this difference, we cannot simply change the GWP value. If we did we would be in the confusing position of having two different GWP values for the same gas, with this variation in accounting tied to where the methane came from.

Indirect CO₂ emissions from the atmospheric oxidation of CH₄ was basically forgotten about by the IPCC when the original guidelines for GHG emission inventories were developed. However the IPCC has recently targeted the issue and is slowly moving to address it in future work.

What is the magnitude of this accounting discrepancy, you ask? Well, it is just under a percent of global emissions (on a GWP-weighted basis), which is not large. But, it is larger than a lot of other source categories we spend a lot of time worrying about. And, for countries with a larger share of fossil methane emissions it can be closer to 2%. More significantly, offset methodologies that fail to account for the effect in coal mine and natural gas projects may produce estimates that are off by 13%.

If you are interested in reading more on this subject, I wrote an academic paper a couple of years ago on it. The abstract is below as well as the link for the full article:

Gillenwater, Michael, “Forgotten carbon: Indirect CO₂ in greenhouse gas emission inventories” Environmental Science and Policy, volume 11, issue 3, May 2008, Pages 195-203.

If you don’t have a subscription to the journal, you can download the pre-publication “discussion paper” version below:

Gillenwater, M., 2007. “Forgotten carbon: Indirect CO₂ in greenhouse gas emission inventories“, [Discussion paper] Science Technology and Environmental Policy Program. Princeton University, Princeton, NJ.

Join leading corporate practitioners, the EPA, the World Resources Institute and the Carbon Disclosure Project for an in-depth conference that will give you everything you need to improve your company’s GHG management program.

Click on the banner (above) to get more information and to register.

What do I mean by infrastructure in this context? I mean those things that enable implementation of policy in all sectors and at all levels. I include in this list:

1. The scientific knowledge necessary to understand the problem and the technologies to address it
2. The legal and regulatory systems to manage the problem
3. In this era of information technology, the information management and decision support systems necessary to address a global problem that is pervasive in its implications
4. The technical standards (i.e., rules, codes, etc.) that facilitate industry and other actors to coordinate and act cost-effectively with high degrees of quality assurance
5. Adequate quantity and quality of human resources to address the problem and educational systems to supply well-trained professionals

There is much work yet to be done to develop the legal and regulatory infrastructure necessary to mitigate GHG emissions. However, as we all are aware, further progress on this front awaits an expanded political consensus.

Significant investment is going into new information technology systems designed to manage GHG emissions in anticipation of future policy and emission markets. Yet, the quality of products available varies widely and is poorly understood. By offering substantive third-party testing, the Institute has begun working to address this opacity.

Globally, the body of standards that will need to be developed to support the range of policies, technologies, and markets is still in its infancy. GHG standards to-date are, for the most part, overly broad and non-specific. The engineering and scientific communities have yet to heavily engage and support the development of more detailed and rigorous standards along the lines of what we see in other industries. And standards development has been systemically hamstrung by the expense and time existing approaches and processes require. However, when you consider the speed and scale at which standards must be developed to keep pace with the demands of a carbon-constrained world, the question of whether existing processes are up to the task emerges. (We will discuss this issue in greater depth in a future blog post detailing the work the GHG Management Institute is undertaking to revolutionize the development of standards, methodologies, protocols, and codes.)

And clearly, the Institute is strongly focused on training and education: building the GHG measurement and management workforce of the future. This has been a key focus since the Institute was founded, and is visible in a range of initiatives from our courses to our developing professional certification program, even our workforce survey.

But, in this blog post, I want to focus more on the first of these infrastructure components: scientific knowledge. The Institute is not a research organization, so our role here is not to generate new science. But as a convening organization, we network GHG professionals from around the world, providing fora for GHG professionals and researchers to develop the intellectual foundation of their new field. One of the key ways we are doing this is with the launch of a peer-reviewed scholarly journal with Earthscan. The journal’s title is Greenhouse Gas Measurement and Management, and it is unique in its focus on the intellectual infrastructure we will need to go beyond just policy debate and design and move onto the serious work of IMPLEMENTATION.

We encourage you to spread the word about this new important journal and to even consider submitting a paper yourself. I hope you agree, that any field without an intellectual base and home will not be successful. And we cannot afford the art and practice of GHG measurement and management to fail.

The aims and scope of the journal are as follows:

Greenhouse Gas Measurement & Management (GHGMM) aims to serve the growing community of professionals dealing with greenhouse gases (GHGs) by providing reliable and up-to-date information on a broad spectrum of relevant issues, including the following:

Measurement of greenhouse gases

• GHG Inventories – application of GHG inventory techniques at all levels (national, organizational, facility and supply-chain-based), including integration of disaggregate level data into national level inventories;
• Measurement, reporting and verification (MRV) – challenges in, and experiences with, the design and/or application of MRV approaches in developed and developing countries;
• Methodologies – lessons learnt from the application of existing methodologies (including application challenges and needed improvements) and from the development of new ones to measure or estimate GHGs from all sources and sinks;
• Uncertainty – managing uncertainty in the measurement or estimation of GHG emissions, removals and storage;
• Quality assurance/Quality control – establishing and enhancing QA/QC procedures, including verification of GHG emissions, removals and storage;
• Best practice – identification of, and experiences with the use of, good practices in measuring GHGs, collecting activity data and identifying appropriate emission factors;
• Sectoral approaches – challenges associated with the estimation/measurement of GHGs from specific sectors and activities;
• Protocols and standards – experiences with the application of various protocols and standards for accounting GHGs;
• GHG and air pollutant emissions – synergies and co-benefits in estimating GHGs and emissions of other air pollutants, including integration or harmonization of reporting requirements;
• Software tools – experiences and challenges with the use of existing, and the development of new, software tools for the estimation/measurement of GHGs;

Markets and projects

• Market-based mechanisms – experiences with the use of market-based mechanisms (including the Kyoto Mechanisms – Emissions trading, Clean Development Mechanism and Joint Implementation) and with the development of reliable project-specific GHG inventory data;
• Additionality, baselines, leakage, permanence – lessons learnt, and experiences with, addressing all of these issues at the international, regional, national, and project level;
• Protocols and standards – experiences with the application of various protocols and standards for project GHG accounting;

Products and technologies

• Best practices – identification of, and experiences with the use of, good practices in designing monitoring, reporting, and verifying GHGs from products and technologies;
• Market-based tools – experiences with the design and implementation of market-based tools for specific products and technologies
• Protocols and standards – experiences with the application of various protocols and standards for product and technology GHG accounting

Management of greenhouse gases

• Accounting – practices relating to accounting for the effects of mitigation measures and determining compliance with specific requirements at all levels;
• Best practice – identification of, and sharing experiences with the use of, good practices in designing systems to monitor, report, and verify GHGs;
• Emissions trends – analysis of, and projections for, GHGs from specific activities, products and technologies;
• Software tools – experiences and challenges with the use of existing, and the development of new, software tools for the accounting, auditing and management of GHGs from mitigation projects, products, technologies;
• Performance measurement – experiences with improving the implementation of mitigation measures and enhancing the management of GHGs;
• Carbon footprint – experiences with the use of different methods/techniques to estimate the carbon footprint of products, practices, and technologies;
• Corporate disclosure and community right to know – risks and opportunities associated with governance issues relating to the management of GHG.

GHGMM will be open to different types of articles, including:

• Original research papers (for example, on topics relating to: theoretical and practical developments on GHGs, concepts and methods, empirical analysis, policy assessments)
• Short communications/Case studies
• Invited reviews
• Opinion pieces/Commentaries
• Book reviews
• Meeting reports

I’m going to skip over the underlying physics and chemistry, because it is not necessary to engage at that level of scientific technicality to be an intelligent user of GWP values.  (If you want to dig into the science more, you can refer to the latest IPCC assessment report published in 2007 — see Chapter 2 of the Working Group I report.)

Global Warming Potentials (GWPs) are a quantified measure of the globally averaged relative radiative forcing impacts of a particular greenhouse gas. It is defined as the cumulative radiative forcing – both direct and indirect effects – integrated over a period of time from the emission of a unit mass of gas relative to some reference gas (IPCC 1996). Carbon dioxide (CO₂) was chosen by the IPCC as this reference gas and its GWP is set equal to one (1).

So to be clear, GWP values are applied to units of mass (e.g., kilograms, pounds, metric tons, etc.) not to units of volume (e.g., cubic meters, cubic feet, liters).

There are three key factors that determine the GWP value of a GHG:

• the gases absorption of infrared radiation,
• where along the electromagnetic spectrum (i.e., what wavelengths) the gas absorbs radiation, and
• the atmospheric lifetime of the gas

We typically only use GWP values for gases that have a long atmospheric lifetime (i.e., in years).  Because only these gases last long enough in the atmosphere to mix evenly and spread throughout the atmosphere to form a relatively uniform concentration. GWP values are meant to be “global,” as the name implies. So if a gas is short-lived and does not have a global concentration because it is destroyed quickly and emitted in different amounts in different places, then it can’t really have a GWP.

Specifically, the gases with relatively long atmospheric lifetimes that tend to be evenly distributed throughout the atmosphere, and therefore have global average concentrations, are CO₂, CH₄, N₂O, HFCs, PFCs, and SF₆. The short-lived gases such as water vapor, carbon monoxide, tropospheric ozone, other ambient air pollutants (e.g., NO_x, and NMVOCs), and tropospheric aerosols (e.g., SO₂ products and black carbon) vary spatially, and consequently it is difficult to quantify their global radiative forcing impacts.

Some GWP values may also account for indirect as well as direct effects. Indirect radiative forcing occurs when chemical transformations involving the original gas produce a gas(es) that is/are also a greenhouse gas, or when a gas influences other radiatively important processes such as the atmospheric lifetimes of other gases.

In sum, the higher the GWP value the more infrared radiation the gas will tend to absorb over its lifetime in the atmosphere. Now, there are three more complications to this story.

The first is that gases will absorb certain wavelengths of radiation. GHGs each absorb in a given “window” of the spectrum. The more that window is filled up, the less there is to absorb. So, as concentrations of certain gases increase they can saturate that wavelength, leaving no more radiation for additional concentrations of gas in the atmosphere to absorb.

The second complication is one that occasionally trips people up. Remember above when we defined GWP by saying “cumulative radiative forcing…integrated over a period of time”? Well, that means that we have to define a time period for the integration to occur. You have to know what the integration period is to make sure you are using the correct GWP. The typical periods that the IPCC publishes are 20, 100, and 500 years.

Now, to be clear, everyone pretty much universally uses 100 year GWP values, so you often never see the time period even cited. But occasionally, someone will use something different, not realizing that they are breaking convention. It is also possible to compute an infinite time horizon GWP value, which would basically mean that accounted for every bit of radiative forcing of every molecule of gas as long as it existed in the atmosphere.

The last complication relates to the fact that the IPCC keeps updating its GWP values with each of its major scientific assessment reports. It makes sense to update GWP values as our scientific understanding improves. However, the problem is that people are using and making commitments based on GWP values while these revisions are taking place. So, say a company or a country says it will reduce its emissions by 10% and achieves that goal. Then all of a sudden GWP values change and now they no longer make the goal if new GWP values are used (due to the mix of different GHGs they emit and reduce). It would be like moving the net after you already kicked the ball towards the goal.

For this reason, the Kyoto Protocol fixed the use of GWP values published by the IPCC in 1996 in its Second Assessment Report. Since then the IPCC has updated its GWP values twice, once in 2001, and again in 2007.  The result has been a proliferation of GWP values out there that leads to a lot of confusion.

Specifically, the Parties to the UNFCCC said:

In addition to communicating emissions in units of mass, Parties may choose also to use global warming potentials (GWPs) to reflect their inventories and projections in carbon dioxide-equivalent terms, using information provided by the Intergovernmental Panel on Climate Change (IPCC) in its Second Assessment Report. Any use of GWPs should be based on the effects of the greenhouse gases over a 100-year time horizon. In addition, Parties may also use other time horizons. (FCCC/CP/1996/15/Add.1)

The major causes for the IPCC’s updates to GWP values involved new laboratory or radiative transfer results, improved atmospheric lifetime estimates, and improved calculations of CO₂ radiative forcing and CO₂ response function. When the radiative forcing of CO₂ is updated, then the GWPs of the other gases relative to CO₂ also change.

The result of the varying time periods and the regular updates by the IPCC is a complicated state of affairs. This table presents GWP values for the most common GHGs (there are many more if we listed all the HFCs, PFCs and other trace gases). As you can see in this table, each gas has number of GWP values that you could chose.

But the truth is, contrary to what a lay person might expect, we typically only use values over a 100 year time period, even though some gases have lifetimes of thousands of years. And we use the old 1995 values, so all the climate change programs and policies around the world, including the Kyoto Protocol, are consistent in their emissions accounting (these GWP values are highlighted in red in the table).

Table: Global Warming Potential Values from the IPCC for some key GHGs

Row 1: 2007 IPCC AR4 (See Chapter 2 of Working Group I report)

Row 2: 2001 IPCC TAR (See Chapter 6 of Working Group I report)

Row 3: 1996 IPCC SAR (See Chapter 2 of the Working Group I report)

To wrap things up for the sake of being thorough, the relationship between mass of a gas and mass of CO₂ Eq. can be expressed as follows:

  mass CO₂ Eq. = (mass of gas) x (GWP)

Where:

  mass CO₂ Eq. = mass (e.g., metric tons) of Carbon Dioxide Equivalents

  GWP = Global Warming Potential

So the calculation is easy. Just multiply the mass of your gas by its GWP value to get CO₂ equivalent emissions. Be sure to label the resulting emissions not as CO₂, but as “CO₂-equivalents.”

And in case you were wondering, according to the IPCC, GWPs typically have an uncertainty of roughly ±35 percent, though some GWPs have larger uncertainty than others.

Previous post in this series.

Back when I was in charge of developing and authoring the official U.S. Inventory of GHG emissions for the U.S. government, I wrote a section for that report on describing GHGs.  To save me some hassle and ensure the background to my later blog posts is provided, I am crimping from the latest U.S. EPA national inventory report.  The text is essentially unchanged since I wrote it several years ago, although the statistics have been updated.

[The following excerpt is taken, with some editing, from the Inventory of U.S. Greenhouse Gas Emissions and Sinks.]

Although the Earth’s atmosphere consists mainly of oxygen and nitrogen, neither plays a significant role in enhancing the greenhouse effect because both are essentially transparent to terrestrial radiation.  The greenhouse effect is primarily a function of the concentration of water vapor, carbon dioxide, and other trace gases in the atmosphere that absorb the terrestrial radiation leaving the surface of the Earth (IPCC 1996).

Changes in the atmospheric concentrations of these greenhouse gases can alter the balance of energy transfers between the atmosphere, space, land, and the oceans.  A gauge of these changes is called radiative forcing, which is a simple measure of changes in the energy available to the Earth-atmosphere system (IPCC 1996).  Holding everything else constant, increases in greenhouse gas concentrations in the atmosphere will produce positive radiative forcing (i.e., a net increase in the absorption of energy by the Earth).

Climate change can be driven by changes in the atmospheric concentrations of a number of radiatively active gases and aerosols.  We have clear evidence that human activities have affected concentrations, distributions and life cycles of these gases (IPCC 1996).

Naturally occurring greenhouse gases include water vapor, carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and ozone (O₃).  Several classes of halogenated substances that contain fluorine, chlorine, or bromine are also greenhouse gases, but they are, for the most part, solely a product of industrial activities.  Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are halocarbons that contain chlorine, while halocarbons that contain bromine are referred to as bromofluorocarbons (i.e., halons).  Because CFCs, HCFCs, and halons are stratospheric ozone depleting substances, they are covered under the Montreal Protocol on Substances that Deplete the Ozone Layer.  The UNFCCC defers to this earlier international treaty; consequently these gases are not included in national greenhouse gas inventories.   Some other fluorine containing halogenated substances—hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆)—do not deplete stratospheric ozone but are potent greenhouse gases.  These latter substances are addressed by the UNFCCC and accounted for in national greenhouse gas inventories.

There are also several gases that, although they do not have a commonly agreed upon direct radiative forcing effect, do influence the global radiation budget.  These tropospheric gases—referred to as ambient air pollutants—include carbon monoxide (CO), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and tropospheric (ground level) ozone (O₃).  Tropospheric ozone is formed by two precursor pollutants, volatile organic compounds (VOCs) and nitrogen oxides (NO_x) in the presence of ultraviolet light (sunlight).  Aerosols—extremely small particles or liquid droplets—often composed of sulfur compounds, carbonaceous combustion products, crustal materials and other human induced pollutants—can affect the absorptive characteristics of the atmosphere.  However, the level of scientific understanding of aerosols is still very low (IPCC 2001).

Carbon dioxide, methane, and nitrous oxide are continuously emitted to and removed from the atmosphere by natural processes on Earth.  Anthropogenic activities, however, can cause additional quantities of these and other greenhouse gases to be emitted or sequestered, thereby changing their global average atmospheric concentrations.  Natural activities such as respiration by plants or animals and seasonal cycles of plant growth and decay are examples of processes that only cycle carbon or nitrogen between the atmosphere and organic biomass.  Such processes—except when directly or indirectly perturbed out of equilibrium by anthropogenic activities—generally do not alter average atmospheric greenhouse gas concentrations over decadal timeframes.  Climatic changes resulting from anthropogenic activities, however, could have positive or negative feedback effects on these natural systems.

Water Vapor (H₂O). Overall, the most abundant and dominant greenhouse gas in the atmosphere is water vapor. Water vapor is neither long-lived nor well mixed in the atmosphere, varying spatially from 0 to 2 percent (IPCC 1996). In addition, atmospheric water can exist in several physical states including gaseous, liquid, and solid. Human activities are not believed to affect directly the average global concentration of water vapor, but the radiative forcing produced by the increased concentrations of other greenhouse gases may indirectly affect the hydrologic cycle. While a warmer atmosphere has an increased water holding capacity, increased concentrations of water vapor affects the formation of clouds, which can both absorb and reflect solar and terrestrial radiation. Aircraft contrails, which consist of water vapor and other aircraft emittants, are similar to clouds in their radiative forcing effects (IPCC 1999).

Carbon Dioxide (CO₂). In nature, carbon is cycled between various atmospheric, oceanic, land biotic, marine biotic, and mineral reservoirs. The largest fluxes occur between the atmosphere and terrestrial biota, and between the atmosphere and surface water of the oceans. In the atmosphere, carbon predominantly exists in its oxidized form as CO₂. Atmospheric CO₂ is part of this global carbon cycle, and therefore its fate is a complex function of geochemical and biological processes. CO₂ concentrations in the atmosphere increased from approximately 280 parts per million by volume (ppmv) in pre-industrial times to 379 ppmv in 2005, a 35 percent increase (IPCC 2007 and Hofmann 2004). The IPCC definitively states that “the present atmospheric CO₂ increase is caused by anthropogenic emissions of CO₂” (IPCC 2001). The predominant source of anthropogenic CO2 emissions is the combustion of fossil fuels. Forest clearing, other biomass burning, and some non-energy production processes (e.g., cement production) also emit notable quantities of CO₂.

In its second assessment, the IPCC also stated that “[t]he increased amount of CO₂ [in the atmosphere] is leading to climate change and will produce, on average, a global warming of the earth’s surface because of its enhanced greenhouse effect—although the magnitude and significance of the effects are not fully resolved” (IPCC 1996).

Methane (CH₄). CH₄ is primarily produced through anaerobic decomposition of organic matter in biological systems. Agricultural processes such as wetland rice cultivation, enteric fermentation in animals, and the decomposition of animal wastes emit CH₄, as does the decomposition of municipal solid wastes. CH₄ is also emitted during the production and distribution of natural gas and petroleum, and is released as a byproduct of coal mining and incomplete fossil fuel combustion. Atmospheric concentrations of CH₄ have increased by about 143 percent since 1750, from a pre-industrial value of about 722 ppb to 1,774 ppb in 2005, although the rate of increase has been declining. The IPCC has estimated that slightly more than half of the current CH₄ flux to the atmosphere is anthropogenic, from human activities such as agriculture, fossil fuel use, and waste disposal (IPCC 2007).

CH₄ is removed from the atmosphere through a reaction with the hydroxyl radical (OH) and is ultimately converted to CO₂. Minor removal processes also include reaction with chlorine in the marine boundary layer, a soil sink, and stratospheric reactions. Increasing emissions of CH₄ reduce the concentration of OH, a feedback that may increase the atmospheric lifetime of CH₄ (IPCC 2001).

Nitrous Oxide (N₂O). Anthropogenic sources of N₂O emissions include agricultural soils, especially production of nitrogen-fixing crops and forages, the use of synthetic and manure fertilizers, and manure deposition by livestock; fossil fuel combustion, especially from mobile combustion; adipic (nylon) and nitric acid production; wastewater treatment and waste combustion; and biomass burning. The atmospheric concentration of N₂O has increased by 18 percent since 1750, from a pre-industrial value of about 270 ppb to 319 ppb in 2005, a concentration that has not been exceeded during the last thousand years. N₂O is primarily removed from the atmosphere by the photolytic action of sunlight in the stratosphere (IPCC 2007).

Ozone. Ozone is present in both the upper stratosphere, where it shields the Earth from harmful levels of ultraviolet radiation, and at lower concentrations in the troposphere, where it is the main component of anthropogenic photochemical “smog.” During the last two decades, emissions of anthropogenic chlorine and bromine-containing halocarbons, such as CFCs, have depleted stratospheric ozone concentrations. This loss of ozone in the stratosphere has resulted in negative radiative forcing, representing an indirect effect of anthropogenic emissions of chlorine and bromine compounds (IPCC 1996). The depletion of stratospheric ozone and its radiative forcing was expected to reach a maximum in about 2000 before starting to recover, with detection of such recovery not expected to occur much before 2010 (IPCC 2001).

The past increase in tropospheric ozone, which is also a greenhouse gas, is estimated to provide the third largest increase in direct radiative forcing since the pre-industrial era, behind CO₂ and CH₄. Tropospheric ozone is produced from complex chemical reactions of volatile organic compounds mixing with NO_x in the presence of sunlight. The tropospheric concentrations of ozone and these other pollutants are short-lived and, therefore, spatially variable (IPCC 2001).

Halocarbons, Perfluorocarbons, and Sulfur Hexafluoride (SF₆). Halocarbons are, for the most part, man-made chemicals that have both direct and indirect radiative forcing effects. Halocarbons that contain chlorine (CFCs, HCFCs, methyl chloroform, and carbon tetrachloride) and bromine (halons, methyl bromide, and hydrobromofluorocarbons [HBFCs]) result in stratospheric ozone depletion and are therefore controlled under the Montreal Protocol on Substances that Deplete the Ozone Layer. Although CFCs and HCFCs include potent global warming gases, their net radiative forcing effect on the atmosphere is reduced because they cause stratospheric ozone depletion, which itself is an important greenhouse gas in addition to shielding the earth from harmful levels of ultraviolet radiation. Ozone depleting gases are covered under the Montreal Protocol and its Amendments and are not covered by the UNFCCC.

HFCs, PFCs, and SF₆ are not ozone depleting substances, and therefore are not covered under the Montreal Protocol. They are, however, powerful greenhouse gases. HFCs are primarily used as replacements for ozone depleting substances but also emitted as a byproduct of the HCFC-22 manufacturing process. Currently, they have a small aggregate radiative forcing impact, but it is anticipated that their contribution to overall radiative forcing will increase (IPCC 2001). PFCs and SF₆ are predominantly emitted from various industrial processes including aluminum smelting, semiconductor manufacturing, electric power transmission and distribution, and magnesium casting. Currently, the radiative forcing impact of PFCs and SF₆ is also small, but they have a significant growth rate, extremely long atmospheric lifetimes, and are strong absorbers of infrared radiation, and therefore have the potential to influence climate far into the future (IPCC 2001).

Carbon Monoxide (CO). Carbon monoxide has an indirect radiative forcing effect by elevating concentrations of CH₄ and tropospheric ozone through chemical reactions with other atmospheric constituents (e.g., the hydroxyl radical, OH) that would otherwise assist in destroying CH₄ and tropospheric ozone. Carbon monoxide is created when carbon-containing fuels are burned incompletely. Through natural processes in the atmosphere, it is eventually oxidized to CO₂. Carbon monoxide concentrations are both short-lived in the atmosphere and spatially variable.

Nitrogen Oxides (NO_x). The primary climate change effects of nitrogen oxides (i.e., NO and NO₂) are indirect and result from their role in promoting the formation of ozone in the troposphere and, to a lesser degree, lower stratosphere, where it has positive radiative forcing effects. Additionally, NO_x emissions from aircraft are likely to decrease CH₄ concentrations, thus having a negative radiative forcing effect (IPCC 1999). Nitrogen oxides are created from lightning, soil microbial activity, biomass burning (both natural and anthropogenic fires), fuel combustion, and, in the stratosphere, from the photo-degradation of N₂O. Concentrations of NO_x are both relatively short-lived in the atmosphere and spatially variable.

Nonmethane Volatile Organic Compounds (NMVOCs). Non-CH₄ volatile organic compounds include substances such as propane, butane, and ethane. These compounds participate, along with NO_x, in the formation of tropospheric ozone and other photochemical oxidants. NMVOCs are emitted primarily from transportation and industrial processes, as well as biomass burning and non-industrial consumption of organic solvents. Concentrations of NMVOCs tend to be both short-lived in the atmosphere and spatially variable.

Aerosols. Aerosols are extremely small particles or liquid droplets found in the atmosphere. They can be produced by natural events such as dust storms and volcanic activity, or by anthropogenic processes such as fuel combustion and biomass burning. Aerosols affect radiative forcing differently than greenhouse gases, and their radiative effects occur through direct and indirect mechanisms: directly by scattering and absorbing solar radiation; and indirectly by increasing droplet counts that modify the formation, precipitation efficiency, and radiative properties of clouds. Aerosols are removed from the atmosphere relatively rapidly by precipitation. Because aerosols generally have short atmospheric lifetimes, and have concentrations and compositions that vary regionally, spatially, and temporally, their contributions to radiative forcing are difficult to quantify (IPCC 2001).

The indirect radiative forcing from aerosols is typically divided into two effects. The first effect involves decreased droplet size and increased droplet concentration resulting from an increase in airborne aerosols. The second effect involves an increase in the water content and lifetime of clouds due to the effect of reduced droplet size on precipitation efficiency (IPCC 2001). Recent research has placed a greater focus on the second indirect radiative forcing effect of aerosols.

Various categories of aerosols exist, including naturally produced aerosols such as soil dust, sea salt, biogenic aerosols, sulfates, and volcanic aerosols, and anthropogenically manufactured aerosols such as industrial dust and carbonaceous aerosols (e.g., black carbon, organic carbon) from transportation, coal combustion, cement production, waste incineration, and biomass burning.

The net effect of aerosols on radiative forcing is believed to be negative (i.e., net cooling effect on the climate), although because they remain in the atmosphere for only days to weeks, their concentrations respond rapidly to changes in emissions. Locally, the negative radiative forcing effects of aerosols can offset the positive forcing of greenhouse gases (IPCC 1996). “However, the aerosol effects do not cancel the global-scale effects of the much longer-lived greenhouse gases, and significant climate changes can still result” (IPCC 1996).

The IPCC’s Third Assessment Report notes that “the indirect radiative effect of aerosols is now understood to also encompass effects on ice and mixed-phase clouds, but the magnitude of any such indirect effect is not known, although it is likely to be positive” (IPCC 2001). Additionally, current research suggests that another constituent of aerosols, black carbon, may have a positive radiative forcing (Jacobson 2001). The primary anthropogenic emission sources of black carbon include diesel exhaust and open biomass burning.

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i) programs or initiatives that attempt to overcome problems of incomplete information by those making investment decisions (e.g., EPA’s Green Lights program),

ii) a related category, eco-labeling, provides information as well as other “warm glow” benefits of a credence good [1],

iii) voluntary emissions reporting and commitment programs (e.g., EPA Climate Leaders),

iv) opt-in provisions for uncapped entities to take on an obligation under a cap-and-trade emissions trading system [2],

v) markets where credit buyers face a scarcity due to an emissions cap but may offset their emissions by purchasing credits from emission reduction projects outside the cap’s boundaries, and

vi) voluntary emission offset markets that do not involve caps on the buying or selling entities and where trading only occurs via emission reduction credits that are calculated relative to an agreed baseline.

As I pointed out before, when we talk about voluntary carbon markets, most people are really referring to category “vi.” So then in my Part 1 post on this question I went on to talk about all the categories except “vi.”

Well, now I return to category “vi,” which is what you probably wanted to hear about in the first place.

This category is typically what people refer to when you or I (or more typically some company) purchases offsets for retirement so they can make claims regarding their own emissions. By purchasing and retiring offsets we intend to compensate for our own emissions.  Effectively, we are paying someone else to reduce in our stead.

Examples of this market include anyone participating in the retirement of credits certified under “voluntary standards” such as the Climate Action Reserve, the Voluntary Carbon Standard, or the Gold Standard.

The concept here is that both the buyers and sellers in the transaction enter the market entirely voluntarily.  There is no regulatory driver creating demand for voluntary market offsets.  Project developers voluntarily develop projects and sell offset credits (this characteristic is common to all offset markets, whether they are part of a “voluntary carbon market” or not) and offset buyers voluntarily purchase them.

The key question for differentiating different types of offset markets is what creates the demand for the credits?  In the case of category “vi,” it is simply a desire to provide a public good to society, which we typically refer to as charity [3].  What is truly interesting about category “vi” offset markets is that they have done something rather unique.  They have commoditized charitable giving in a way that attempts to directly measure a public good, meaning they measure a uniform unit improvement in the public welfare.

Other environmental commodities have been created and trade voluntarily, like Renewable Energy Certificates (RECs), but they typically do not actually represent a unit change in a public good.  Instead they represent a unit of activity occurring that we assume or hope produces a public good. Specifically, in the case of RECs, all we know is that a mega-watt hour of electricity was generated by someone.  We don’t know whether the commodity we bought and retired (i.e., the REC) produced a change for the better.  It could have had no effect on anything the renewable generator did [4] [5]. As many of you know, what I am getting at is the issue of additionality.

When you stop to think about it, there is a powerful lesson here.  What other areas of charity could we create commodities for?  Vaccinations?  Calories for the starving?  Education (e.g., in the form of improved test score results) for the disadvantaged?

A powerful idea, that goes beyond just environmental economics.

Endnotes:

[1] Baksi, S. and P. Bose (2007). “Credence Goods, Efficient Labeling Policies, and Regulatory Enforcement.” Environmental and Resource Economics 37(2): 411-430.

[2] The fraction of entities mandated to participate versus the fraction that voluntarily opt-in can vary from zero to one.  For example, under the U.S. Acid Rain program, the ratio is essentially one (mandatory), while for non-governmental systems, such as the Chicago Climate Exchange, the ratio is zero (entirely voluntary).

[3] See http://www.nature.com/climate/2007/0711/full/climate.2007.58.html#B4

[4] Gillenwater, M., Redefining RECs (Part 1): Untangling attributes and offsets, Energy Policy, Volume 36, Issue 6, June 2008, Pages 2109-2119.

[5]Gillenwater, M., Redefining RECs (Part 2): Untangling certificates and emission markets, Energy Policy, Volume 36, Issue 6, June 2008, Pages 2120-2129.