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PROJECT PLANS

2002: Methane Emissions: An Alternative Scenario for Fossil Fuel

Introduction

Methane (CH4) is a potent greenhouse gas about 25 times more efficient at trapping heat in the Earth's atmosphere than is carbon dioxide (CO2) on a molecule-for-molecule basis. Although a great deal of scientific research and press coverage is devoted to CO2, the growth of methane concentrations accounts for about 20% to the total radiative forcing over the last century, or about 40% that of CO2. Direct measurements of atmospheric methane concentrations, begun in 1983, show that CH4 levels have increased each year, but that the rate of growth slowed down during the 1990s. Since the atmosphere reflects the net effect of CH4 sources (inputs) and sinks (removals), the observed decline in growth rate signals that sources stabilized or declined, and/or that sinks increased. Overall research of the Methane Team is designed to investigate the possible contribution of changes in sources, over the last decades, to the declining growth rate of atmospheric methane.

Anthropogenic (human-related) sources such as flooded-rice cultivation, enteric fermentation in ruminant animals, landfills, biomass burning, and fossil-fuel production and consumption account for about 70% of annual methane emissions. Wetlands are the only significant natural source of methane, as well as being the largest single source. Because wetlands are responsive to climate, their methane emissions show large interannual variations due to interannual climate fluctuations although wetland emissions show no decadal trend. Therefore, if sources are contributing to changes observed in the growth of atmospheric methane, the sources are anthropogenic.

Previous ICP research has focused on initial estimates of annual emissions from several sources for 1980 onward; these sources are natural wetlands, rice cultivation, enteric fermentation in ruminants, landfills, and fossil fuel production, transport and processing. ICP methane research for the summer of 2002 will focus on several related components in order to improve our understanding of the global methane cycle. These include: improving/refining historical estimates of several sources, reducing uncertainties in source estimates, improving our ability to predict future emissions which is necessary in order to develop ways to successfully reduce projected emissions, and disseminating our results and educational materials, as well as inviting participation by other middle schools in our research via web materials.

Science Questions

What are the major uncertainties in the current methane budget? Which sources, regions, and/or time periods contribute to these uncertainties? How can we reduce these uncertainties?

What criteria should be applied to assessing and/or improving projections for future methane emissions? Can we develop and use such criteria to assess whether several families of current projections represent plausible future emissions?

Research Objectives

In past ICP research summers, research projects of the methane team were very tightly integrated. For the summer of 2002, we anticipate undertaking a suite of related but free-standing projects that build upon our previous work. The projects are designed to achieve the following objectives: reduce uncertainties in existing source estimates (Task 1), improve/refine emission histories for individual sources (Tasks 2 and 3), evaluate and develop techniques to improve our ability to predict future methane emissions (Tasks 4 and 5), and disseminate results and educational materials (Task 6). Initial outlines of potential projects follow. Specific tasks, data sources, and other information about how we anticipate the progress of the research projects is provided in Appendix 1.

So far, team members have selected the projects they will focus on but we also anticipate crossover/collaboration on some projects. Project 2 was of lower priority and therefore remains unchosen at present. The current choice of research projects is as follows:

Reduce Uncertainties in Fossil Fuel Emission Estimates

We have previously developed annual emission estimates for all countries for 1980-1998 for all relevant methane-producing processes for fossil fuels (coal, oil and natural gas). The largest uncertainty in this work is fugitive emissions from venting and flaring of natural gas at gas and oil wells. One project this summer will focus on obtaining data on venting/flaring amounts by country and year wherever possible. These data will eventually be used to recalculate methane emissions from this process. This work, by relying on venting/flaring data, will reduce uncertainties in our earlier estimates calculated using general emission factors prescribing fractions of total gas and oil production released as methane in venting/flaring processes. CC will search for (and hopefully obtain) the data. DS will integrate these data into the new calculation of emissions from venting /flaring of oil and gas since he carried out the initial calculations in 2001 and therefore is very familiar with the data sets.

Integrate New Measurements Into Emission Estimates

One project may concentrate on designing and beginning to develop a data base of methane-emission measurements for rice, together with information on environment, management, climate, soil chemistry, etc. as reported with the scientific literature or obtained elsewhere (e.g. meteorological stations). This work will initiate the first component in addressing an identified weakness in emission estimates for rice cultivation -- the imbalance between the major effort spent to measure methane emissions from a large number of rice environments and the minimal effort spent to compile information on the distribution of these environments in order to apply the measurements appropriately.

Confirm Management Information Used in Emission Estimates

Primary researcher CC. Our current estimate of historical methane emissions from rice cultivation (1980-1998) varies over time primarily as a function of changing harvest area; information on water management (e.g., % area irrigated, rain fed, dry) was available for 1990 only and we had to assume that proportions of rice area under various water-management schemes in 1990 remained constant over time. New information from the International Rice Research Institute (IRRI) and available from EM provides information on water management for all rice producers for 1980, 1985, 1990, and 1995, as well as information on seasonality of up to 3 rice crops/year. This project will analyze IRRI statistics for these 4 time periods to determine whether water management has changed over time and by how much. If it has changed substantially, using 1990 conditions for all years, as done previously, is not justified and rice emissions will be recalculated using the new information. If water management has remained generally stable, using 1990 conditions for all years does not introduce errors assuming that the 1990 information currently used is accurate.

Therefore, even if water management has remained stable over time, we must still assess whether the "representative" 1990 values used for all years are similar or the same as the 1990 values recently reported by IRRI. If they are different, we will revise our historical estimates so that they will still rely on a single representative profile of water management applied to all years, but that profile will reflect the new IRRI statistics. If the 1990 information we previously used for all years is confirmed to be accurate using the new IRRI information as the standard, the analysis is valuable in that it will have reduced an uncertainty in our previous estimate. Specific tasks/decisions that have to be done/made for this project include the following: 1) decide what constitutes a "substantial change" in water management practices over time (and therefore what constitutes "constant" water practices).

Assess Future Emission Projections

We can use the emission time series we have developed for anthropogenic sources of methane to identify the factors that controlled emission trends for the past in order to assess the likelihood of several alternative scenarios proposed for future emissions. One concept is to undertake an exercise to look at the projected change in several source emissions between 2000 to 2020 for 4 major regions and 4 major methane sources (rice, ruminant animals, fossil fuels, and landfills) for 4 scenarios developed by other researchers. Potential scenarios are IPCC SRES A1B (something like a business as usual scenario), IPCC SRES A2 (reflecting generally higher development rates and higher emissions than SRES A1B), an "optimistic" scenario (based on US projections and assuming that all countries will have the technology/financial resources to control emissions as efficiently as the US while at the same time pursuing development), and EPA2002 (based on new EPA materials that attempt to project emissions to the year 2020 and beyond assuming that growth rates in the late 1990's will continue into the future). This analysis will provide us with substantive information regarding the probability that the suggested scenarios are realistic. It will also provide valuable input to assessments of the Hansen et al. Alternative Scenario which stipulates that methane emissions must decline to 70% of 1990 levels.

Develop Future Emission Projections

We will focus on a single methane source (probably rice cultivation) and develop future projections for that source using plausible constraints derived from past emission trends and results of Project 4. For example, emission projections are frequently made using estimates of increases in product demands derived from estimates of population growth. However, emissions for some sources are not, or may not be, closely tied to population while for other sources, the technical advancements required to fulfill the projected demand are beyond plausible limits for development. Either case can result in projected emissions that may be theoretically possible but extremely unlikely. Similar to initial work on assessing projections (above), we will use our time series of emissions by country to identify factors that controlled past trends in order to enhance approaches to projecting plausible emissions for the future. In the case of rice, emissions have been very stable for the last 20 years despite the fact that rice production increased >40%. Increased production came from improved yields per harvest, while harvest area remained relatively stable. Since harvest area is the primary controller of methane emissions, the rice methane source remained relatively stable during the period of dramatic rises in production. Despite this situation, projections of future rice-related methane emissions usually assume that demand will increase AND more importantly, that this demand will be satisfied; it is also usually assumed that the higher demand for rice will be satisfied by increases in harvest area. For this research task, we will impose constraints on how increased demand for rice can be achieved; for example, we will assume that production must increase in the same way/s that production increases were accomplished in the past. This analysis will allow us to evaluate, in a more realistic context, various scenarios proposed for future emissions as well as to propose new scenarios for consideration.

Finalize Methane Web Materials

Since the Methane Team began in 1996, we have written (and rewritten and rewritten) a set of materials including 1) Introduction to the Greenhouse Effect, Greenhouse Gases, and Global Warming, 2) Introduction to the Global Methane Cycle, 3) Teachers' Manual with background materials and lessons related to the global methane project, 4) Learning Modules, and 5) ICP Research Results. We will edit, correct, sort through, etc. these materials, make final decisions about which and how materials should be provided via the web, develop additional materials if needed, and complete the final web page for the methane project. D. Sarma will be taking primary responsibility for this task, but all members are welcome and encouraged to contribute ideas, assist in editing and decision-making, and help prepare needed materials.

Science understandings and skills students should have or develop

The plan for researchers to develop these understandings and skills is outlined in Appendix 1, Guidance for Research Projects

Science Understandings

  • What is the natural greenhouse effect? What is the perturbed greenhouse effect?
  • What is a greenhouse gas?
  • What is methane composed of & why is it important in carbon & climate studies?
  • What is a definition of "source" and "sink" (in general terms)
  • What are the major sources of methane? the major sinks of methane?
  • How have methane concentrations changed over the last few hundred years? Over the last few decades?
  • Which sources do we know relatively well, and which are less well understood (and why)? E.g., do we understand the processes of methane production for a source pretty well but do not have a good handle on how that source's methane emissions are distributed over space or time? Remember: level of understanding can translate into level of un/certainty
  • What are the major uncertainties in methane sources?
  • What is the focus of our 2002 research with respect to reducing uncertainties?

Skills

  • search/read literature to educate yourself about the problem, what has been done before, where your project fits in/contributes etc.
  • develop/strengthen working knowledge of Word, Excel
  • search for data (web, literature, library)
  • obtain/format data, and extract only what you need for your project if the data set contains more than you need.
  • use naming conventions for data sets (hints in Appendix 2) so that others can get a good idea what is in your data sets without having to track you down
  • carry out calculations on large data sets (our technique is to make sure the method works for 1 year of data before going on to other years - if you are doing multiple years of calculations)
  • learn how to quickly quality-control data to check for errors or locate an error you know is there somewhere
  • sharpen use of the "common sense" evaluation of methods/data/results (do the numbers make sense? are there odd/anomalous features in the data?
  • plot intermediate and final results in order to see them from several perspectives
  • organize and write a science paper
  • summarize results in an understandable and accurate way
  • know/learn how to reference work that you used for your project (articles, books, edited books, reports, data received on CD;s or disks, web pages)
  • acknowledge collaborators, people who helped with data, discussions, etc.
  • organize and prepare a science presentation (refer to (the real) document prepared by the American Geophysical Union entitled "How To Give a Truly Terrible Talk). Tips include: use incredibly small fonts on your plots, make tables with many many columns and rows with small numbers that you never refer to, talk really fast, wave your hands around alot - preferably directly in front of the screen, don't introduce the science problem in the beginning but jump right into details of your methodology, face and talk to the screen and not the audience, mumble or talk softly.

List of team readings

  • Background materials on the ICP Methane web page
    • Introduction to the Greenhouse Effect, Greenhouse Gases, and Global Warming
    • Introduction to the Global Methane Cycle
  • Crutzen, P.J., Methane sources and sinks, Nature, 350, 380-381, 1991.
  • Dlugokencky, E.J., L.P. Steele, P.M. Lang, and K.A. Masarie, The growth rate and distribution of atmospheric methane, J. Geophys. Res., 99, 17,021-17,043, 1994.
  • Khalil, M.A.K., Atmospheric Methane: Its Role in the Global Environment, Springer-Verlag, Berlin, 2000 (book with chapters on different aspects of methane cycle with particular focus on sources, available in office all summer).
  • Wang, Y., Global Tropospheric OH: Observational constraints and model simulations, provided by author, 2000.

Appendix 1. Guidance for Research Projects

Project 3. Confirm Management Information Used in Emission Estimates

Our current estimate of historical methane emissions from rice cultivation (1980-1998) varies over time primarily as a function of changing harvest area; information on water management (e.g., % area irrigated, rainfed, dry) was available for 1990 only and we had to assume that proportions of rice area under various water-management schemes in 1990 remained constant over time. New information from the International Rice Research Institute (IRRI) and available from EM provides information on water management for all rice producers for 1980, 1985, 1990, and 1995, as well as information on seasonality of up to 3 rice crops/year. This project will analyze IRRI statistics for these 4 time periods to determine whether water management has changed over time and by how much. If it has changed substantially, using 1990 conditions for all years, as done previously, is not justified and rice emissions will be recalculated using the new information. If water management has remained generally stable, using 1990 conditions for all years does not introduce errors *assuming that the 1990 information currently used is accurate.* Therefore, even if water management has remained stable over time, we must still assess whether the "representative" 1990 values used for all years are similar or the same as the 1990 values recently reported by IRRI. If they are different, we will revise our historical estimates so that they will still rely on a single representative profile of water management applied to all years, but that profile will reflect the new IRRI statistics. If the 1990 information we previously used for all years is confirmed to be accurate using the new IRRI information as the standard, the analysis is valuable in that it will have reduced an uncertainty in our previous estimate.

What will be available to researchers to start the project:

  • ICP data set: includes, for every year and all rice-producing countries, the rice harvest area, fraction of area under 3 water-management regimes (irrigated, rainfed, dryland - these values reflect 1990 conditions but have been held constant for each year), methane emission factors (amount of methane emitted per unit area per year for rice managed under 3 water regimes), and total annual methane emissions for all years, countries, and water-management rice groups.
  • IRRI data for all rice-producing countries for 1980, 1985, 1990 and 1995 on: rice areas under different water management regimes, seasonality of rice crops, and sometimes other pertinent information for rice cropping.

Roadmap and products

  • Assessing change in water management practices. Determine what constitutes a "substantial change" in water management practices over time (and therefore what constitutes "constant" water practices). There is no firm rule and method to do this. The crucial thing is to determine criteria (objective or subjective) that can be consistently applied to the existing data set and the IRRI data, and explain very clearly what the criteria are and how they were determined. The criteria could be something like the following: variations in the fraction of rice harvest area under specific water management regimes are considered "constant" if they vary within ±2% of the historical mean, and considered to vary "substantially" if they vary more than ±2% of the historical mean.
  • Apply change criteria. Apply the criteria to derive a list of all countries indicating which have "constant" water management regimes and which have variable regimes.
  • Calculate historical methane emissions for "varying" countries. Countries with "varying" practices require that the new IRRI information is used to recalculate the emission history. It is clear what to do for the years 1980, 1985, 1990 and 1995 since those are the years for which specific water-management data are available. Redoing calculations for the intervening years will require making decisions about how to "connect" the information between "data years". You might assume that the change that occurred between 2 data years was equally distributed in the intervening years. Calculate emissions for all years and all countries with new water management data. Keep the other countries' emissions in the data set.
  • Assess accuracy of 1990 water management data. For countries with constant water management over time, assess whether the "representative" 1990 values previously used for all years are accurate by comparing them to the 1990 values recently reported by IRRI. It will be necessary to decide how similar these values must be to be "accurate" . For example, you may just want to change over to using the 1990 IRRI values for all countries except where the data are identical between the older values and the new IRRI ones.
  • Calculate historical methane emissions for "constant" countries. Recalculate historical emissions for all countries applying the new representative values for water management for each country from IRRI to all years.
  • Describe/analyze changes/constancy in water management. Discuss/describe which countries have/have not experienced changes in water management; make connection with the expected influence on methane emissions.
  • Describe/analyze new emission history. Discuss features of the new emission history (maybe global, then focus on some regions, . . . ) Compare to our previous history in order to identify the impact of the new information on methane emissions.
  • Discussion/Conclusion. How does this research help to understand the role of rice in the declining growth rate of atmospheric methane, . . .

Project 4 of Project 4/5 - Assess Future Emission Scenarios

We can use the emission time series we have developed for anthropogenic sources of methane to identify the factors that controlled emission trends for the past in order to assess the likelihood of several alternative scenarios proposed for future emissions. One concept is to undertake an exercise to look at the projected change in several source emissions between 2000 to 2020 for 4 major regions and 4 major methane sources (rice, ruminant animals, fossil fuels, and landfills) for 4 scenarios developed by other researchers. Potential scenarios are IPCC SRES A1B (something like a business as usual scenario), IPCC SRES A2 (reflecting generally higher development rates and higher emissions than SRES A1B), an "optimistic" scenario (based on US projections and assuming that all countries will have the technology/financial resources to control emissions as efficiently as the US while at the same time pursuing development), and EPA2002 (based on new EPA materials that attempt to project emissions to the year 2020 and beyond assuming that growth rates in the late 1990's will continue into the future). This analysis will provide us with substantive information regarding the probability that the suggested scenarios are realistic. It will also provide valuable input to assessments of the Hansen et al. Alternative Scenario which stipulates that methane emissions must decline to 70% of 1990 levels.

What will be available to researchers to start the project:

  • A data table giving the proportional relationship between methane emissions for 2020 relative to 1990 for 4 regions and several sources for four scenarios. For example, if between 1990 and 2020, emissions increased by 25% for animals in Asia, the number in the table is 1.25 (2020 emissions = 1.25 × 1990 emissions)
  • 1990 methane emissions, in units of teragrams (1 Tg = 1012 g), for all regions, sources, and scenarios.
  • Materials (e.g., IPCC Scenario book, EPA documents) describing the assumptions etc. underlying the scenarios

Roadmap and products

  • Calculate 2020 emissions: Multiply 1990 emissions (Tg CH4 for sources, regions and scenarios) by proportional increases between 1990 and 2020 for those sources, regions, and scenarios (these values are given in the table) to get 2020 emissions in Tg (this is the easiest and fastest part). Regional results can be merged into a table that summarizes sources and scenarios for regions and for the globe.
  • Characterize scenarios. Organize information (maybe into a table) characterizing the four scenarios in order to illuminate differences and similarities among them. You might first take notes about the scenarios, and identify categories of assumptions, such as economic, technological, social/population, agricultural. This information would probably go into a table with brief comments about the assumptions of the scenarios (e.g., rapid economic development, low technological development, ...). The table might have a column listing the assumptions or sources that exert primary control on the change in emissions between 1990 & 2020 (e.g., fossil fuels, animals,
  • Describe/Analyze scenarios. Analyze/compare/contrast the scenarios referring to the table but providing more detail than available there. Explain what "rapid technological development" means (or whatever characteristics you identified). This information is available in the IPCC scenario book that I have and that I used to develop the initial table of ratios.
  • Describe/Analyze emissions. Analyze/compare/contrast the emissions: How large are changes (proportional etc.)? What sources (if any) controlled the change in emissions for each scenario? What sources varied the most between 1990 and 2020 among the scenarios? What source showed the largest range for predicted changes in emissions among the scenarios? What sources (if any) showed little variation among the scenarios? Do large/small ranges for individual sources indicate large/small uncertainty? What sources are the best candidates for reducing uncertainties in predictions/scenarios?
  • Conclusions. Which scenarios/sources are more plausible than others?

Project 5 of Project 4/5 - Develop Future Emission Scenarios

We may focus on a single methane source (probably rice cultivation) and develop future projections for that source using plausible constraints derived from past emission trends. For example, emission projections are frequently made using estimates of increases in product demands derived from estimates of population growth. However, emissions for some sources are not, or may not be, closely tied to population while for other sources, the technical advancements required to fulfill the projected demand are beyond plausible limits for development. Either case can result in projected emissions that may be theoretically possible but extremely unlikely. Similar to initial work on assessing projections (Task 4 above), we will use our time series of emissions by country to identify factors that controlled past trends in order to enhance approaches to projecting plausible emissions for the future. In the case of rice, emissions have been very stable for the last 20 years despite the fact that rice production increased >40%. Increased production came from improved yields per harvest, while harvest area remained relatively stable. Since harvest area is the primary controller of methane emissions, the rice methane source remained relatively stable during the period of dramatic rises in production. Despite this situation, projections of future rice-related methane emissions usually assume that demand will increase AND more importantly, that this demand will be satisfied; it is also usually assumed that the higher demand for rice will be satisfied by increases in harvest area. For this research task, we will impose constraints on how increased demand for rice can be achieved; for example, we will assume that production must increase in the same way/s that production increases were accomplished in the past. This analysis will allow us to evaluate, in a more realistic context, various scenarios proposed for future emissions (see Project 4 of Project 4/5) as well as to propose new scenarios for consideration.

What will be available to researchers to start the project:

  • historical data (most in electronic form) of data on rice production, rice yield, rice-harvest area, human population, fertilizer use (limited data) for rice-producing countries
  • 1990 information on water management practices for all rice-producing countries; these data consist of fractions of harvest rice area in 3 regimes: irrigated, rainfed, and dryland (the latter does not produce methane)
  • seasonality of rice crops for all countries (planting and harvest months) and characteristic fractions of total harvest area in each of the crops for each country (from Matthews et al., 1991 paper)
  • lots of pages of data from IRRI, organized by country, on aspects of rice cultivation such as water management practices, seasonality of crops, types of rice cultivars (we probably won't use this now), etc.

Roadmap and products

  • Characterize historical trends in rice area, production, and yield, and in human population. How has each of these changed over time?
  • Analyze historical relationships among rice area, production, and yield, and human population. Which of these vary in similar ways and which do not? What variable/variables govern/s the change in production over time? Is production becoming decoupled from a variable? Coupled with a variable?
  • Future production scenarios. Using projections of rice demand/production from several scenarios, come up with various ways that the demand in production could be satisfied. This might include assuming that production rise by increases in area, increases in yield, or a combination of the two. You could impose constraints based on your historical analysis, e.g., production rises via increases in area and yield contribute proportionally as they did in the past.
  • Calculate future methane emissions for your scenarios. Remembering that methane emissions are controlled almost exclusively by area, calculate future methane emissions for the scenarios you have developed.
  • Asses the plausibility of your scenarios. Given the historical and current status of rice cultivation, how plausible are your scenarios? How plausible are the scenarios developed by other researchers.