Tg CO2 Research Articles

DAYCENT National‐Scale Simulations of Nitrous Oxide Emissions from Cropped Soils in the United States

Until recently, Intergovernmental Panel on Climate Change (IPCC) emission factor methodology, based on simple empirical relationships, has been used to estimate carbon (C) and nitrogen (N) fluxes for regional and national inventories. However, the 2005 USEPA greenhouse gas inventory includes estimates of N2O emissions from cultivated soils derived from simulations using DAYCENT, a process-based biogeochemical model. DAYCENT simulated major U.S. crops at county-level resolution and IPCC emission factor methodology was used to estimate emissions for the approximately 14% of cropped land not simulated by DAYCENT. The methodology used to combine DAYCENT simulations and IPCC methodology to estimate direct and indirect N2O emissions is described in detail. Nitrous oxide emissions from simulations of presettlement native vegetation were subtracted from cropped soil N2O to isolate anthropogenic emissions. Meteorological data required to drive DAYCENT were acquired from DAYMET, an algorithm that uses weather station data and accounts for topography to predict daily temperature and precipitation at 1-km2 resolution. Soils data were acquired from the State Soil Geographic Database (STATSGO). Weather data and dominant soil texture class that lie closest to the geographical center of the largest cluster of cropped land in each county were used to drive DAYCENT. Land management information was implemented at the agricultural-economic region level, as defined by the Agricultural Sector Model. Maps of model-simulated county-level crop yields were compared with yields estimated by the USDA for quality control. Combining results from DAYCENT simulations of major crops and IPCC methodology for remaining cropland yielded estimates of approximately 109 and approximately 70 Tg CO2 equivalents for direct and indirect, respectively, mean annual anthropogenic N2O emissions for 1990-2003.

Interactive chemistry in the Laboratoire de Météorologie Dynamique general circulation model: model description and impact analysis of biogenic hydrocarbons on tropospheric chemistry

Abstract. We present a description and evaluation of LMDz-INCA, a global three-dimensional chemistry-climate model, pertaining to its recently developed NMHC version. In this substantially extended version of the model a comprehensive representation of the photochemistry of non-methane hydrocarbons (NMHC) and volatile organic compounds (VOC) from biogenic, anthropogenic, and biomass-burning sources has been included. The tropospheric annual mean methane (9.2 years) and methylchloroform (5.5 years) chemical lifetimes are well within the range of previous modelling studies and are in excellent agreement with estimates established by means of global observations. The model provides a reasonable simulation of the horizontal and vertical distribution and seasonal cycle of CO and key non-methane VOC, such as acetone, methanol, and formaldehyde as compared to observational data from several ground stations and aircraft campaigns. LMDz-INCA in the NMHC version reproduces tropospheric ozone concentrations fairly well throughout most of the troposphere. The model is applied in several sensitivity studies of the biosphere-atmosphere photochemical feedback. The impact of surface emissions of isoprene, acetone, and methanol is studied. These experiments show a substantial impact of isoprene on tropospheric ozone and carbon monoxide concentrations revealing an increase in surface O3 and CO levels of up to 30 ppbv and 60 ppbv, respectively. Isoprene also appears to significantly impact the global OH distribution resulting in a decrease of the global mean tropospheric OH concentration by approximately 0.7×105 molecules cm-3 or roughly 8% and an increase in the global mean tropospheric methane lifetime by approximately seven months. A global mean ozone net radiative forcing due to the isoprene induced increase in the tropospheric ozone burden of 0.09 W m-2 is found. The key role of isoprene photooxidation in the global tropospheric redistribution of NOx is demonstrated. LMDz-INCA calculates an increase of PAN surface mixing ratios ranging from 75 to 750 pptv and 10 to 250 pptv during northern hemispheric summer and winter, respectively. Acetone and methanol are found to play a significant role in the upper troposphere/lower stratosphere (UT/LS) budget of peroxy radicals. Calculations with LMDz-INCA show an increase in HOx concentrations region of 8 to 15% and 10 to 15% due to methanol and acetone biogenic surface emissions, respectively. The model has been used to estimate the global tropospheric CO budget. A global CO source of 3019 Tg CO yr-1 is estimated. This source divides into a primary source of 1533 Tg CO yr-1 and secondary source of 1489 Tg CO yr-1 deriving from VOC photooxidation. Global VOC-to-CO conversion efficiencies of 90% for methane and between 20 and 45% for individual VOC are calculated by LMDz-INCA.

Ecosystem carbon budgeting and soil carbon sequestration in reclaimed mine soil

Global warming risks from emissions of green house gases (GHGs) by anthropogenic activities, and possible mitigation strategies of terrestrial carbon (C) sequestration have increased the need for the identification of ecosystems with high C sink capacity. Depleted soil organic C (SOC) pools of reclaimed mine soil (RMS) ecosystems can be restored through conversion to an appropriate land use and adoption of recommended management practices (RMPs). The objectives of this paper are to (1) synthesize available information on carbon dioxide (CO 2) emissions from coal mining and combustion activities, (2) understand mechanisms of SOC sequestration and its protection, (3) identify factors affecting C sequestration potential in RMSs, (4) review available methods for the estimation of ecosystem C budget (ECB), and (5) identify knowledge gaps to enhance C sink capacity of RMS ecosystems and prioritize research issues. The drastic perturbations of soil by mining activities can accentuate CO 2 emission through mineralization, erosion, leaching, changes in soil moisture and temperature regimes, and reduction in biomass returned to the soil. The reclamation of drastically disturbed soils leads to improvement in soil quality and development of soil pedogenic processes accruing the benefit of SOC sequestration and additional income from trading SOC credits. The SOC sequestration potential in RMS depends on amount of biomass production and return to soil, and mechanisms of C protection. The rate of SOC sequestration ranges from 0.1 to 3.1 Mg ha − 1 yr − 1 and 0.7 to 4 Mg ha − 1 yr − 1 in grass and forest RMS ecosystem, respectively. Proper land restoration alone could off-set 16 Tg CO 2 in the U.S. annually. However, the factors affecting C sequestration and protection in RMS leading to increase in microbial activity, nutrient availability, soil aggregation, C build up, and soil profile development must be better understood in order to formulate guidelines for development of an holistic approach to sustainable management of these ecosystems. The ECBs of RMS ecosystems are not well understood. An ecosystem method of evaluating ECB of RMS ecosystems is proposed.

Spatial and temporal patterns of carbon emissions from forest fires in China from 1950 to 2000

We have estimated the emission of carbon (C) and carbon‐containing trace gases including CO2, CO, CH4, and NMHC (nonmethane hydrocarbons) from forest fires in China for the time period from 1950 to 2000 by using a combination of remote sensing, forest fire inventory, and terrestrial ecosystem modeling. Our results suggest that mean annual carbon emission from forest fires in China is about 11.31 Tg per year, ranging from a minimum level of 8.55 Tg per year to a maximum level of 13.9 Tg per year. This amount of carbon emission is resulted from the atmospheric emissions of four trace gases as follows: (1) 40.66 Tg CO2 with a range from 29.21 to 47.53 Tg, (2) 2.71 Tg CO with a range from 1.48 to 4.30 Tg, (3) 0.112 Tg CH4 with a range from 0.06 to 0.2 Tg, and (4) 0.113 Tg NMHC with a range from 0.05 to 0.19 Tg. Our study indicates that fire‐induced carbon emissions show substantial interannual and decadal variations before 1980 but have remained relatively low and stable since 1980 because of the application of fire suppression. Large spatial variation in fire‐induced carbon emissions exists due to the spatial variability of climate, forest types, and fire regimes.

Estimation of the contribution of intercontinental transport during the PEACE campaign by using a global model

A quasi–real–time calculation system for the global distribution of ozone (O3) and its precursors, including CO, NOx, and nonmethane hydrocarbons (NMHCs), has been newly developed by using a 3–D chemical–transport model. The model is driven by meteorological data from the National Centers for Environmental Prediction (NCEP), and produces daily 7–day forecast of the distribution of chemical species. The model was used in daily flight planning for the Pacific Exploration of Asian Continental Emission (PEACE)–A and –B aircraft measurement campaigns in January and April–May 2002, respectively. Model–calculated meteorological fields show good agreement with aircraft observations. The model also reproduced events such as polluted air masses in the lower troposphere (LT) corresponding to post–frontal outflow, a high–concentration CO plume in the upper troposphere (UT) in late spring, and the observed plume that was transported by deep convection over central China. The amount of CO transported into the free troposphere (FT) by deep convection was estimated to be about 6 Tg CO over China in May 2002. Meridional and seasonal variations in the long–range transport (LRT) of CO tracers, Asian CO tracers, and CO tracers produced from the oxidation of CH4 and NMHCs were all evaluated using tagged CO tracers. LRT CO comprised about 36% of the total CO budget in December–February 2001/2002, and about 20% in March–May 2002 in the free troposphere over Japan. In late spring, the concentration of Asian CO over southern Japan decreased compared to that in winter because the wind direction shifted from northwesterly to easterly or southerly.

Emissions from international shipping: 1. The last 50 years

Seagoing ships emit exhaust gases and particles into the marine boundary layer and significantly contribute to the total budget of anthropogenic emissions. We present an emission inventory for international shipping for the past five decades to be used in global modeling studies with detailed tropospheric chemistry. The inventory is a bottom‐up analysis using fuel consumption and fleet numbers for the total civilian and military fleet including auxiliary engines at the end of 2001. Trend estimates for fuel mass, CO2, NOx, and other emissions for the time between 1950 and 2001 have been calculated using ship number statistics and average engine statistics. Our estimate for total fuel consumption and global emissions for the year 2001 is similar to previous activity‐based studies. However, compared to earlier studies, a detailed speciation of nonmethane hydrocarbons (NMHCs) and particulate matter is given, and carbon monoxide emissions are calculated explicitly. Our results suggest a fuel consumption of approximately 280 million metric tons (Mt) for the year 2001 and 64.5 Mt in 1950. This corresponds to 187 (5.4) Tg CO2 (NOx) in 1950, and 813 (21.4) Tg CO2 (NOx) in 2001. From 1970 to 2001 the world‐merchant fleet increased rapidly in terms of ship numbers, with a corresponding increase in total fuel consumption. The fuel consumption estimates are compared against historical marine bunker fuel statistics, and our emission estimates are related to emission budgets of other transport modes. Global ship emissions are distributed geographically according to global vessel traffic densities of the AMVER (Automated Mutual‐assistance Vessel Rescue system) data set for the year 2000. This work also sets the basis to develop future emission scenarios based on average‐fleet emission indices in part 2 of this study.

Greenhouse gas emissions from Indian rice fields: calibration and upscaling using the DNDC model

Abstract. The Denitrification and Decomposition (DNDC) model was evaluated for its ability to simulate methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions from Indian rice fields with various management practices. The model was calibrated and validated for field experiments in New Delhi, India. The observed yield, N uptake and greenhouse gas (GHG) emissions were in good agreement with the values predicted by the model. The model was then applied for estimation of GHG emissions from rice fields in India using a newly compiled soil/climate/land use database. Continuous flooding of rice fields (42.25 million ha) resulted in annual net emissions of 1.07-1.10, 0.04-0.05 and 21.16-60.96 Tg of CH4-C, N2O-N and CO2-C, respectively, with a cumulated global warming potential (GWP) of 130.93-272.83 Tg CO2 equivalent. Intermittent flooding of rice fields reduced annual net emissions to 0.12-0.13 Tg CH4-C and 16.66-48.80 Tg CO2-C while N2O emission increased to 0.05-0.06 Tg N2O-N. The GWP, however, reduced to 91.73-211.80 Tg CO2 equivalent. The study suggested that the model could be applied for estimating the GHG emissions and the influences of agronomic management, soil and climatic parameters on the GHG emissions from rice fields in India.

Inversion of CO and NO<sub>x</sub> emissions using the adjoint of the IMAGES model

Abstract. We use ground-based observations of CO mixing ratios and vertical column abundances together with tropospheric NO2 columns from the GOME satellite instrument as constraints for improving the global annual emission estimates of CO and NOx for the year 1997. The agreement between concentrations calculated by the global 3-dimensional CTM IMAGES and the observations is optimized using the adjoint modelling technique, which allows to invert for CO and NOx fluxes simultaneously, taking their chemical interactions into account. Our analysis quantifies a total of 39 flux parameters, comprising anthropogenic and biomass burning sources over large continental regions, soil and lightning emissions of NOx, biogenic emissions of CO and non-methane hydrocarbons, as well as the deposition velocities of both CO and NOx. Comparison between observed, prior and optimized CO mixing ratios at NOAA/CMDL sites shows that the inversion performs well at the northern mid- and high latitudes, and that it is less efficient in the Southern Hemisphere, as expected due to the scarsity of measurements over this part of the globe. The inversion, moreover, brings the model much closer to the measured NO2 columns over all regions. Sensitivity tests show that anthropogenic sources exhibit weak sensitivity to changes of the a priori errors associated to the bottom-up inventory, whereas biomass burning sources are subject to a strong variability. Our best estimate for the 1997 global top-down CO source amounts to 2760 Tg CO. Anthropogenic emissions increase by 28%, in agreement with previous inverse modelling studies, suggesting that the present bottom-up inventories underestimate the anthropogenic CO emissions in the Northern Hemisphere. The magnitude of the optimized NOx global source decreases by 14% with respect to the prior, and amounts to 42.1 Tg N, out of which 22.8 Tg N are due to anthropogenic sources. The NOx emissions increase over Tropical regions, whereas they decrease over Europe and Asia. Our inversion results have been evaluated against independent observations from aircraft campaigns. This comparison shows that the optimization of CO emissions constrained by both CO and NO2 observations leads to a better agreement between modelled and observed values, especially in the Tropics and the Southern Hemisphere, compared to the case where only CO observations are used. A posteriori estimation of errors on the control parameters shows that a significant error reduction is achieved for the majority of the anthropogenic source parameters, whereas biomass burning emissions are still subject to large errors after optimization. Nonetheless, the constraints provided by the GOME measurements allow to reduce the uncertainties on savanna burning emissions of both CO and NOx, suggesting thus that the incorporation of these data in the inversion yields more robust results for carbon monoxide.

Historical CO 2 emission and concentrations due to land use change of croplands and pastures by country

This work is aimed at estimating the historical land use change emission and concentrations of CO 2 by country. Calculating the area differences of each biome (associated to carbon factors) converted to cropland (including urban areas) and pastures by country we calculated the land use change CO 2 emission over the past 300 years using a new dataset, which is a well known one in the literature: the HYDE land use database. According to IPCC-SR-LULUCF (2000) the net cumulative global CO 2 emission from land use change (1850–1990) is estimated to have been 499±205 Tg CO 2, our result is 360 Tg CO 2 for the same period, and Houghton's (Houghton, RA, 2003a. Revised estimates of the annual net flux of carbon to the atmosphere from changes in land use and land management 1850–2000. Tellus 55B, 378–390) result is 492 Tg CO 2. We have also used the Bern model (IPCC-TAR-WG1, 2001) of decay time of CO 2 to estimate the concentrations of CO 2 in the year 1990 due to land use change emission, once the CO 2 emission from the past is still decaying in the atmosphere.

Influences of boreal fire emissions on Northern Hemisphere atmospheric carbon and carbon monoxide

There were large interannual variations in burned area in the boreal region (ranging between 3.0 and 23.6 × 106 ha yr−1) for the period of 1992 and 1995–2003 which resulted in corresponding variations in total carbon and carbon monoxide emissions. We estimated a range of carbon emissions based on different assumptions on the depth of burning because of uncertainties associated with the burning of surface‐layer organic matter commonly found in boreal forest and peatlands, and average total carbon emissions were 106–209 Tg yr−1 and CO emissions were 33–77 Tg CO yr−1. Burning of ground‐layer organic matter contributed between 46 and 72% of all emissions in a given year. CO residuals calculated from surface mixing ratios in the high Northern Hemisphere (HNH) region were correlated to seasonal boreal fire emissions in 8 out of 10 years. On an interannual basis, variations in area burned explained 49% of the variations in HNH CO, while variations in boreal fire emissions explained 85%, supporting the hypotheses that variations in fuels and fire severity are important in estimating emissions. Average annual HNH CO increased by an average of 7.1 ppb yr−1 between 2000 and 2003 during a period when boreal fire emissions were 26 to 68 Tg CO−1 higher than during the early to mid‐1990s, indicating that recent increases in boreal fires are influencing atmospheric CO in the Northern Hemisphere.

The contribution of agricultural lime to carbon dioxide emissions in the United States: dissolution, transport, and net emissions

Abstract Agricultural lime (aglime) is commonly applied to soils in the eastern U.S. to increase soil pH. Aglime includes crushed limestone (CaCO 3 ) and crushed dolomite (MgCa(CO 3 ) 2 ). Following the supposition by the Intergovernmental Panel on Climate Change (IPCC) that all C in aglime is eventually released as CO 2 to the atmosphere, the U.S. EPA estimated that 9 Tg (Teragram = 10 12 g = 10 6 metric tonne) CO 2 was emitted from an approximate 20 Tg of applied aglime in 2001. A review of historic data on aglime production and use indicates that 30 Tg may better represent the annual U.S. consumption of aglime. More importantly, our review of terrestrial and ocean C dynamics indicates that it is unlikely that all C from aglime is released to the atmosphere following application to soils. On the contrary, the primary pathway for aglime dissolution is reaction with carbonic acid (H 2 CO 3 ) which results in uptake of CO 2 . Depending on soil pH and nitrogen fertilizer use, a fraction of aglime may react with strong acid sources such as nitric acid (HNO 3 ), thereby releasing CO 2 . Data on soil leaching and river transport of calcium (Ca 2+ ) and bicarbonate (HCO 3 − ) suggest that a significant portion of dissolved aglime constituents may leach through the soil and be transported by rivers to the ocean. Much of the fraction transported to the ocean will precipitate as CaCO 3 . Bicarbonate remaining in the soil profile is expected to release CO 2 following re-acidification of the soil over time. Our analysis indicates that net CO 2 emissions from the application of aglime is 0.059 Mg C per Mg limestone and 0.064 Mg C per Mg dolomite. This is in contrast to IPCC estimates of 0.12 and 0.13 Mg C per Mg limestone and dolomite, respectively. Based on our best estimate, the application of 20–30 Tg of aglime in the U.S., consisting of 80% limestone and 20% dolomite, would have resulted in a net 4.4–6.6 Tg CO 2 emissions in 2001.

Pollution by cereal waste burning in Spain

In this paper, the amount of cereal waste burned in Spain, which represents the most important source of biomass burning in this country, is estimated. During the period between 1980 and 1998, an average mass of 8 Tg of cereal waste was burned annually, with remaining 1 Tg of ash on the cereal fields after combustion. By using emission factors previously calculated by Ortiz de Zárate et al. [Ortiz de Zárate, I., Ezcurra, A., Lacaux, J.P., Van Dihn, P., 2000. Emission factor estimates of cereal waste burning in Spain. Atmos. Environ. 34, 3183–3193.], it is deduced that pollutant emissions linked to cereal waste-burning process reach values of 11 Tg CO 2, 80 Gg of TPM and 23 Gg of NO x year −1 during the cereal-burning period. These emissions represent 46% of total CO 2 and 23% NO x emitted in Spain during the burning period that lasts 1 month after harvesting. Therefore, the relative importance of cereal waste burning as pollutant source in Spain almost during fire period becomes evident. Finally, our study allows to deduce that the production of 1 kg of cereal crop implies that 410 g of carbon and 3.3 g of nitrogen are going to be introduced into the atmosphere by this pollutant process. We estimate a total gaseous emission of 3.3 Tg of C and 25 Gg N as different pollutants by cereal waste burning.

Long‐range transport of Siberian biomass burning emissions and impact on surface ozone in western North America

During the summer of 2003, biomass fires burned a large area of Siberia, the largest in at least 10 years. We used the NRL Aerosol Analysis and Prediction System (NAAPS) model to forecast the transport of the smoke from these fires. Transport of these airmasses to North America was confirmed by aircraft and surface observations. The fires resulted in enhancements in summer background CO and O3of 23–37 and 5–9 ppbv, respectively, at 10 sites in Alaska, Canada and the Pacific Northwest. From the area burned, we estimate that the Siberian fires generated 68 Tg of CO and 0.82 Tg of NOx(as N). In addition, we show that the background O3enhancement contributed to an exceedance of the ozone air quality standard in the Pacific Northwest. These results show that regional air quality and health are linked to global processes, including climate, forest fires and long‐range transport of pollutants.

Sink Potential of Canadian Agricultural Soils

Net greenhouse gas (GHG) emissions from Canadian crop and livestock production were estimated for 1990, 1996 and 2001 and projected to 2008. Net emissions were also estimated for three scenarios (low (L), medium (M) and high (H)) of adoption of sink enhancing practices above the projected 2008 level. Carbon sequestration estimates were based on four sink-enhancing activities: conversion from conventional to zero tillage (ZT), reduced frequency of summerfallow (SF), the conversion of cropland to permanent cover crops (PC), and improved grazing land management (GM). GHG emissions were estimated with the Canadian Economic and Emissions Model for Agriculture (CEEMA). CEEMA estimates levels of production activities within the Canadian agriculture sector and calculates the emissions and removals associated with those levels of activities. The estimates indicate a decline in net emissions from 54 Tg CO2–Eq yr−1 in1990 to 52 Tg CO2–Eq yr−1 in 2008. Adoption of thesink-enhancing practices above the level projected for 2008 resulted in further declines in emissions to 48 Tg CO2–Eq yr−1 (L), 42 TgCO2–Eq yr−1 (M) or 36 Tg CO2–Eq yr−1 (H). Among thesink-enhancing practices, the conversion from conventional tillage to ZT provided the largest C sequestration potential and net reduction in GHG emissions among the scenarios. Although rates of C sequestration were generally higher for conversion of cropland to PC and adoption of improved GM, those scenarios involved smaller areas of land and therefore less C sequestration. Also, increased areas of PC were associated with an increase in livestock numbers and CH4 and N2O emissions from enteric fermentation andmanure, which partially offset the carbon sink. The CEEMA estimates indicate that soil C sinks are a viable option for achieving the UNFCCC objective of protecting and enhancing GHG sinks and reservoirs as a means of reducing GHG emissions (UNFCCC, 1992).

Remote sensing and geographic information systems methods for global spatiotemporal modeling of biomass burning emissions: Assessment in the African continent

A spatially explicit model for analysis of biomass burning emissions is presented. The model, based on that of Seiler and Crutzen [1980], uses satellite images and geographic information systems (GIS) modeling tools to improve the estimation of biomass loads and burning efficiency. The model was assessed in the African continent using the Global Burned Area (GBA‐2000) maps derived from SPOT‐Vegetation by the Joint Research Center. A total amount of 5711.78 and 336.43 Tg CO was estimated from the model. The areas south of the equator were estimated to release 3579.22 and 218.21Tg CO, while 2132.56 and 118.22 Tg CO were estimated for the Northern Hemisphere. Most of these emissions were generated by two latitude strips: between 3.5° and 11°N, and between 5° and 13°S. Monthly variability shows a clear bimodal temporal behavior, with two maxima in November–February in the northern band and in June–September in the southern band. The effect of biomass loads distribution on gas emissions is clearly shown, with higher gas emissions in the Southern Hemisphere in spite of having lower burned extension.

Global Wildland Fire Emission Model (GWEM): Evaluating the use of global area burnt satellite data

The new Global Wildland Fire Emission Model (GWEM) has been developed on the basis of data from the European Space Agency's monthly Global Burnt Scar satellite product (GLOBSCAR) and results from the Lund‐Potsdam‐Jena Dynamic Global Vegetation Model (LPJ‐DGVM). GWEM computes monthly emissions of more than 40 chemical compounds and aerosols from forest and savanna fires. This study focuses on an evaluation of the GLOBSCAR data set. The GWEM version presented here makes use of the Moderate‐Resolution Imaging Spectroradiometer (MODIS) land cover map. Emission totals for the year 2000 are 1741 Tg C, 5716 Tg CO2, 271 Tg CO, 12.52 Tg CH4, 9.09 Tg C (as nonmethane hydrocarbons), 8.08 Tg NOx (as NO), 24.30 Tg PM2.5, 15.80 Tg OC, and 1.84 Tg black carbon. These emissions are lower than other estimates found in literature. An evaluation assesses the uncertainties of the individual input data. The GLOBSCAR product yields reasonable estimates of burnt area for large wildland fires in most parts of the globe but experiences problems in some regions where small fires dominate. The seasonality derived from GLOBSCAR differs from other satellite products detecting active fires owing to the different algorithms applied. Application of the presented GWEM results in global chemistry transport modeling will require additional treatment of small deforestation fires in the tropical rain forest regions and small savanna fires, mainly in subequatorial Africa. Further improvements are expected from a more detailed description of the carbon pools and the inclusion of anthropogenic disturbances in the LPJ model.

Global estimates of biomass burning emissions based on satellite imagery for the year 2000

A synthesis of ground‐based measurements and satellite information is described for estimating the amount of monthly averaged biomass burned in year 2000 with a spatial resolution of 1 × 1 km on a global scale. Emissions of trace gases and aerosols from open biomass burning are estimated from burned areas, fuel load maps, combustion factors, and emission factors. Burned area was quantified by using satellite data in conjunction with a fractional vegetation cover map. To account for spatial heterogeneity in the main types of vegetation within each 1‐km grid cell, global fuel load maps have been developed from biomass density data sets for herbaceous and tree‐covered land together with global fractional tree and vegetation cover maps. In regions with 40–60% tree cover a relationship between combustion completeness (or combustion factor) in fine fuels and tree cover based on recent field studies is implemented. In regions with <40% tree cover the combustion factor and emissions are related to global satellite‐derived data for leaf area index. In regions with >60% tree cover and for coarse fuels in regions with 40–60% tree cover, average values for combustion factors and emission factors from field measurements are used. In addition to biomass burning from open vegetation fires, the emissions from biofuel burning in 2000 are estimated. Our best estimate for the global amount of burned biomass in 2000 is 5613 Tg DM yr−1, of which 2814 Tg DM yr−1is associated with open burning and the remainder with biofuels. The total emissions are 2290 Tg C yr−1(as CO2), 496 Tg CO yr−1, 32.2 Tg CH4yr−1, 38.0 Tg NHMC yr−1, 11.5 Tg HCHO yr−1, 9.2 Tg CH3OH yr−1, 21.7 Tg CH3COOH yr−1, and 38.3 Tg PM2.5yr−1. Our estimates for CO2, CO, and CH4emissions from open biomass burning combined with estimates of those from biofuel burning are in the range of the estimates constrained by chemical transport models and measurements. Our use of spatially and temporally explicit data and these comparisons to global models support the conclusion that our source map offers improvements in the emission data sets for estimating the global effects of biomass burning.

An inventory of gaseous and primary aerosol emissions in Asia in the year 2000

An inventory of air pollutant emissions in Asia in the year 2000 is developed to support atmospheric modeling and analysis of observations taken during the TRACE‐P experiment funded by the National Aeronautics and Space Administration (NASA) and the ACE‐Asia experiment funded by the National Science Foundation (NSF) and the National Oceanic and Atmospheric Administration (NOAA). Emissions are estimated for all major anthropogenic sources, including biomass burning, in 64 regions of Asia. We estimate total Asian emissions as follows: 34.3 Tg SO2, 26.8 Tg NOx, 9870 Tg CO2, 279 Tg CO, 107 Tg CH4, 52.2 Tg NMVOC, 2.54 Tg black carbon (BC), 10.4 Tg organic carbon (OC), and 27.5 Tg NH3. In addition, NMVOC are speciated into 19 subcategories according to functional groups and reactivity. Thus we are able to identify the major source regions and types for many of the significant gaseous and particle emissions that influence pollutant concentrations in the vicinity of the TRACE‐P and ACE‐Asia field measurements. Emissions in China dominate the signature of pollutant concentrations in this region, so special emphasis has been placed on the development of emission estimates for China. China's emissions are determined to be as follows: 20.4 Tg SO2, 11.4 Tg NOx, 3820 Tg CO2, 116 Tg CO, 38.4 Tg CH4, 17.4 Tg NMVOC, 1.05 Tg BC, 3.4 Tg OC, and 13.6 Tg NH3. Emissions are gridded at a variety of spatial resolutions from 1° × 1° to 30 s × 30 s, using the exact locations of large point sources and surrogate GIS distributions of urban and rural population, road networks, landcover, ship lanes, etc. The gridded emission estimates have been used as inputs to atmospheric simulation models and have proven to be generally robust in comparison with field observations, though there is reason to think that emissions of CO and possibly BC may be underestimated. Monthly emission estimates for China are developed for each species to aid TRACE‐P and ACE‐Asia data interpretation. During the observation period of March/April, emissions are roughly at their average values (one twelfth of annual). Uncertainties in the emission estimates, measured as 95% confidence intervals, range from a low of ±16% for SO2 to a high of ±450% for OC.

Biomass burning in Asia: Annual and seasonal estimates and atmospheric emissions

Estimates of biomass burning in Asia are developed to facilitate the modeling of Asian and global air quality. A survey of national, regional, and international publications on biomass burning is conducted to yield consensus estimates of “typical” (i.e., non‐year‐specific) estimates of open burning (excluding biofuels). We conclude that 730 Tg of biomass are burned in a typical year from both anthropogenic and natural causes. Forest burning comprises 45% of the total, the burning of crop residues in the field comprises 34%, and 20% comes from the burning of grassland and savanna. China contributes 25% of the total, India 18%, Indonesia 13%, and Myanmar 8%. Regionally, forest burning in Southeast Asia dominates. National, annual totals are converted to daily and monthly estimates at 1° × 1° spatial resolution using distributions based on AVHRR fire counts for 1999–2000. Several adjustment schemes are applied to correct for the deficiencies of AVHRR data, including the use of moving averages, normalization, TOMS Aerosol Index, and masks for dust, clouds, landcover, and other fire sources. Good agreement between the national estimates of biomass burning and adjusted fire counts is obtained (R2= 0.71–0.78). Biomass burning amounts are converted to atmospheric emissions, yielding the following estimates: 0.37 Tg of SO2, 2.8 Tg of NOx, 1100 Tg of CO2, 67 Tg of CO, 3.1 Tg of CH4, 12 Tg of NMVOC, 0.45 Tg of BC, 3.3 Tg of OC, and 0.92 Tg of NH3. Uncertainties in the emission estimates, measured as 95% confidence intervals, range from a low of ±65% for CO2emissions in Japan to a high of ±700% for BC emissions in India.

Simulated Farm Fieldwork, Energy Consumption and Related Greenhouse Gas Emissions in Canada

The amount of greenhouse gas (GHG) emissions that can be attributed to agricultural machinery management was analysed using computer simulation of farm power requirements, machine hours and fuel consumption. The ‘Farm Fieldwork and Fossil Fuel Energy and Emissions’ (F4E2) model optimised tractor and harvester power P. To minimise P for a single tractor for spring tillage and sowing, the model budgets available spring work time in half-day increments and adjusts implement widths to match. Other field operations in the model are powered by a tractor derived for spring. Emissions of GHG were estimated for ploughing, discing and sowing operations in springs, along with autumn harvesting, cultivation for weeds, spreading manure and sprying for pests. A grain trailer and a swather were considered as part of harvesting. Farm site estimates were extrapolated to regional and national scales with appropriate and available Canadian Census and farm survey data. Fuel consumption and GHG emission factors for petrol and diesel fuels were also analysed. Fuel efficiency and proper matching of equipment to tractors were important factors. Canada's 1996 Farm Energy Use Survey (FEUS) provided useful validation to the F4E2 energy consumption estimates. The model estimate of 71·6 PJ of diesel energy for 1996 was within 1% of the 72·0 PJ of diesel fuel energy that FEUS attributes to farm machinery for Canada. The 1990 Kyoto baseline estimate of GHG emissions was 6·5 Tg of CO 2 equivalent from both diesel and petrol for farm field operations in Canada.