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Net terrestrial CO2 exchange over China during 2001-2010 estimated with an ensemble data assimilation system for atmospheric CO 2
Zhang, H.F. ; Chen, B.Z. ; Laan-Luijkx, I.T. van der; Peters, W. ; Chen, J. ; Xu, G. ; Yan, J.W. ; Zhou, X. ; Fukuyama, Y. ; Tans, P.P. - \ 2014
Journal of Geophysical Research: Atmospheres 119 (2014)6. - ISSN 2169-897X - p. 3500 - 3515.
carbon-dioxide exchange - flux inversion - north-america - ecosystems - sinks - transport - surface - temperature - forests - trends
In this paper we present an estimate of net ecosystem CO2 exchange over China for the years 2001–2010 using the CarbonTracker Data Assimilation System for CO2 (CTDAS). Additional Chinese and Asian CO2 observations are used in CTDAS to improve our estimate. We found that the combined terrestrial ecosystems in China absorbed about -0.33 Pg C yr-1 during 2001–2010. The uncertainty on Chinese terrestrial carbon exchange estimates as derived from a set of sensitivity experiments suggests a range of -0.29 to -0.64 Pg C yr-1. This total Chinese terrestrial CO2 sink is attributed to the three major biomes (forests, croplands, and grass/shrublands) with estimated CO2 fluxes of -0.12 Pg C yr-1 (range from -0.09 to -0.19 Pg C yr-1), -0.12 Pg C yr-1 (range from -0.09 to -0.26 Pg C yr-1), and -0.09 Pg C yr-1 (range from -0.09 to -0.17 Pg C yr-1), respectively. The peak-to-peak amplitude of interannual variability of the Chinese terrestrial ecosystem carbon flux is 0.21 Pg C yr-1 (~64% of mean annual average), with the smallest CO2 sink (-0.19 Pg C yr-1) in 2003 and the largest CO2 sink (-0.40 Pg C yr-1) in 2007. We stress that our estimate of terrestrial ecosystem CO2 uptake based on inverse modeling strongly depends on a limited number of atmospheric CO2 observations used. More observations in China specifically and in Asia in general are needed to improve the accuracy of terrestrial carbon budgeting for this region
Habitat functionality for the ecosystem service of pest control: reproduction and feeding sites of pests and natural enemies
Bianchi, F.J.J.A. ; Schellhorn, N.A. ; Cunningham, S.A. - \ 2013
Agricultural and Forest Entomology 15 (2013)1. - ISSN 1461-9555 - p. 12 - 23.
agricultural landscapes - coccinellidae - agroecosystems - biodiversity - assemblages - coleoptera - density - aphids - sinks
1 Landscape management for enhanced natural pest control requires knowledge of the ecological function of the habitats present in the landscape mosaic. However, little is known about which habitat types in agricultural landscapes function as reproduction habitats for arthropod pests and predators during different times of the year. 2 We studied the arthropod assemblage on six crops and on the seven most abundant native plant species in two landscapes over 1 year in Australia. Densities of immature and adult stages of pests and their predators were assessed using beat sheet sampling. 3 The native plants supported a significantly different arthropod assemblage than crops. Native plants had higher predator densities than crops over the course of the year, whereas crops supported higher pest densities than the native plants in two out of four seasonal sampling periods. Crops had higher densities of immature stages of pests than native plants in three of four seasonal sampling periods, implying that crops are more strongly associated with pest reproduction than native plants. Densities of immature predators, excluding spiders, were not different between native plants and crops. Spiders were, however, generally abundant and densities were higher on native plants than on crops but, because some species disperse when immature, there is less certainty in identifying their reproduction habitat. 4 Because the predator to pest ratio on native plant species showed little variation, and spatial variation in arthropod assemblages was limited, the predator support function of native vegetation may be a general phenomenon. Incentives that maintain and restore native remnant vegetation can increase the predator to pest ratio at the landscape scale, which could enhance pest suppression in crops.
Global atmospheric carbon budget: results from an ensemble of atmospheric CO2 inversions.
Peylin, P. ; Law, R.M. ; Gurney, K.R. ; Chevallier, F. ; Jacobsen, A.R. ; Maki, T. ; Niwa, Y. ; Patra, P.K. ; Peters, W. ; Rayner, P.J. ; Rödenbeck, C. ; Laan-Luijkx, I.T. van der; Zhang, X. - \ 2013
Biogeosciences 10 (2013). - ISSN 1726-4170 - p. 6699 - 6720.
interannual variability - dioxide exchange - transport model - sinks - fluxes - sensitivity - ocean - land - cycle - emissions
Atmospheric CO2 inversions estimate surface carbon fluxes from an optimal fit to atmospheric CO2 measurements, usually including prior constraints on the flux estimates. Eleven sets of carbon flux estimates are compared, generated by different inversions systems that vary in their inversions methods, choice of atmospheric data, transport model and prior information. The inversions were run for at least 5 yr in the period between 1990 and 2010. Mean fluxes for 2001-2004, seasonal cycles, interannual variability and trends are compared for the tropics and northern and southern extra-tropics, and separately for land and ocean. Some continental/basin-scale subdivisions are also considered where the atmospheric network is denser. Four-year mean fluxes are reasonably consistent across inversions at global/latitudinal scale, with a large total (land plus ocean) carbon uptake in the north (-3.4 Pg C yr(-1) (+/- 0.5 Pg C yr(-1) standard deviation), with slightly more uptake over land than over ocean), a significant although more variable source over the tropics (1.6 +/- 0.9 Pg C yr(-1)) and a compensatory sink of similar magnitude in the south (-1.4 +/- 0.5 Pg C yr(-1)) corresponding mainly to an ocean sink. Largest differences across inversions occur in the balance between tropical land sources and southern land sinks. Interannual variability (IAV) in carbon fluxes is larger for land than ocean regions (standard deviation around 1.06 versus 0.33 Pg C yr(-1) for the 1996-2007 period), with much higher consistency among the inversions for the land. While the tropical land explains most of the IAV (standard deviation similar to 0.65 Pg C yr(-1)), the northern and southern land also contribute (standard deviation similar to 0.39 Pg C yr(-1)). Most inversions tend to indicate an increase of the northern land carbon uptake from late 1990s to 2008 (around 0.1 Pg C yr(-1)), predominantly in North Asia. The mean seasonal cycle appears to be well constrained by the atmospheric data over the northern land (at the continental scale), but still highly dependent on the prior flux seasonality over the ocean. Finally we provide recommendations to interpret the regional fluxes, along with the uncertainty estimates.
Importance of fossil fuel emission uncertainties over Europe for CO2 modeling: model intercomparison
Peylin, P. ; Houweling, S. ; Krol, M.C. ; Karstens, U. ; Rödenbeck, C. - \ 2011
Atmospheric Chemistry and Physics 11 (2011)13. - ISSN 1680-7316 - p. 6607 - 6622.
atmospheric transport models - part 1 - land - inversions - (co2)-c-14 - fluxes - sinks
Inverse modeling techniques used to quantify surface carbon fluxes commonly assume that the uncertainty of fossil fuel CO2 (FFCO2) emissions is negligible and that intra-annual variations can be neglected. To investigate these assumptions, we analyzed the differences between four fossil fuel emission inventories with spatial and temporal differences over Europe and their impact on the model simulated CO2 concentration. Large temporal flux variations characterize the hourly fields (~40 % and ~80 % for the seasonal and diurnal cycles, peak-to-peak) and annual country totals differ by 10 % on average and up to 40 % for some countries (i.e., the Netherlands). These emissions have been prescribed to seven different transport models, resulting in 28 different FFCO2 concentrations fields. The modeled FFCO2 concentration time series at surface sites using time-varying emissions show larger seasonal cycles (+2 ppm at the Hungarian tall tower (HUN)) and smaller diurnal cycles in summer (-1 ppm at HUN) than when using constant emissions. The concentration range spanned by all simulations varies between stations, and is generally larger in winter (up to ~10 ppm peak-to-peak at HUN) than in summer (~5 ppm). The contribution of transport model differences to the simulated concentration std-dev is 2–3 times larger than the contribution of emission differences only, at typical European sites used in global inversions. These contributions to the hourly (monthly) std-dev's amount to ~1.2 (0.8) ppm and ~0.4 (0.3) ppm for transport and emissions, respectively. First comparisons of the modeled concentrations with 14C-based fossil fuel CO2 observations show that the large transport differences still hamper a quantitative evaluation/validation of the emission inventories. Changes in the estimated monthly biosphere flux (Fbio) over Europe, using two inverse modeling approaches, are relatively small (less that 5 %) while changes in annual Fbio (up to ~0.15 % GtC yr-1) are only slightly smaller than the differences in annual emission totals and around 30 % of the mean European ecosystem carbon sink. These results point to an urgent need to improve not only the transport models but also the assumed spatial and temporal distribution of fossil fuel emission inventories.
The seasonal cycle amplitude of total column CO2: Factors behind the model-observation mismatch
Basu, S. ; Houweling, S. ; Peters, W. ; Sweeney, C. ; Machida, T. ; Maksyutov, S. - \ 2011
Journal of Geophysical Research: Atmospheres 116 (2011)D23. - ISSN 2169-897X - 14 p.
carbon-dioxide exchange - in-situ observations - atmospheric co2 - lower stratosphere - transport - inversion - sinks - constraints - calibration - delta-c-13
CO2 surface fluxes that are statistically consistent with surface layer measurements of CO2, when propagated forward in time by atmospheric transport models, underestimate the seasonal cycle amplitude of total column CO2 in the Northern temperate latitudes by 1-2 ppm (Yang et al, 2007). In this manuscript we verify the systematic nature of this underestimation at a number of TCCON stations by comparing their measurements with a number of transport models. In particular, at Park Falls, Wisconsin (USA) we estimate this mismatch to be 1.4 ppm, and try to attribute portions of this mismatch to different factors affecting the total column. We find that errors due to the averaging kernel and prior used in forward models, water vapor in the model atmosphere, incorrect vertical transport by transport models in the free troposphere, incorrect aging of air in transport models in the stratosphere, and airmass dependence in TCCON data can explain up to 1 ppm of this mismatch. The remaining 0.4 ppm mismatch is at the edge of the accuracy requirement on satellite measurements to improve on our current estimate of surface fluxes. Uncertainties in the biosphere fluxes driving the transport models could explain a part of the remaining mismatch, implying that with corrections to the factors behind the accounted-for 1 ppm underestimation, present inverse modeling frameworks could effectively assimilate satellite CO2 measurements.
Continuous measurements of atmospheric oxygen and carbon dioxide on a North Sea gas platform
Laan-Luijkx, I.T. van der; Neubert, R.E.M. ; Laan, S. van der; Meijer, H.A.J. - \ 2010
Atmospheric Measurement Techniques 3 (2010)1. - ISSN 1867-1381 - p. 113 - 125.
klimaatverandering - kooldioxide - emissie - meting - noordzee - climatic change - carbon dioxide - emission - measurement - north sea - o-2/n-2 ratio - co2 - air - o-2 - cycle - sinks - analyzer - trend
A new atmospheric measurement station has been established on the North Sea oil and gas production platform F3, 200 km north off the Dutch coast (54°51' N, 4°44' E). Atmospheric concentrations of O2 and CO2 are continuously measured using fuel cell technology and compact infrared absorption instruments, respectively. Furthermore, the station includes an automated air flask sampler for laboratory analysis of the atmospheric concentrations of CO2, CH4, CO and O2 and isotope measurements of d13C, d18O and ¿14C from CO2. This station is the first fixed sea based station with on-site continuous O2 and CO2 measurements and therefore yields valuable information about the CO2 uptake in coastal marine regions, specifically the North Sea. This paper presents the measurement station and the used methodologies in detail. In comparison to land-based stations, the data show low day-to-day variability, as they are practically free of nightly inversions as well as human influences, due to the station’s remoteness. Therefore, the data set collected at this measurement station serves directly as background data for the coastal northwest European region. Additionally, the first data are presented showing the seasonal cycle as expected during August 2008 through June 2009. Furthermore, some short-term O2 and CO2 signals are presented. The observations at the platform include several large and fast changing negative atmospheric O2 excursions without an accompanying change in the CO2 signal, which most likely indicate marine O2 uptake
CO2, dO2/N2 and APO: observations from the Lutjewad, Mace Head and F3 platform flask sampling network
Laan-Luijkx, I.T. van der; Karstens, U. ; Steinbach, J. ; Gerbig, C. ; Sirignano, C. ; Neubert, R.E.M. ; Laan, S. van der; Meijer, H.A.J. - \ 2010
Atmospheric Chemistry and Physics 10 (2010)21. - ISSN 1680-7316 - p. 10691 - 10704.
atmospheric oxygen measurements - global carbon-cycle - gas-chromatograph - o-2/n-2 ratio - o-2 - air - variability - dioxide - sinks - emissions
We report results from our atmospheric flask sampling network for three European sites: Lutjewad in the Netherlands, Mace Head in Ireland and the North Sea F3 platform. The air samples from these stations are analyzed for their CO2 and O2 concentrations. In this paper we present the CO2 and O2 data series from these sites between 1998 and 2009, as well as the atmospheric potential oxygen (APO). The seasonal pattern and long term trends agree to a large extent between our three measurement locations. We however find a changing gradient between Mace Head and Lutjewad, both for CO2 and O2. To explain the potential contribution of fossil fuel emissions to this changing gradient we use an atmospheric transport model in combination with CO2 emission data and information on the fossil fuel mix per region. Using the APO trend from Mace Head we obtain an estimate for the global oceanic CO2 uptake of 1.8 ± 0.8 PgC/year.
A Carbon Cycle Science Update Since IPCC AR-4
Dolman, A.J. ; Werf, G.R. van der; Molen, M.K. van der; Ganssen, G. ; Erisman, J.W. ; Strengers, B. - \ 2010
Ambio 39 (2010)5-6. - ISSN 0044-7447 - p. 402 - 412.
climate-change - co2 emissions - terrestrial plants - atmospheric co2 - forests - sinks - feedbacks - trends - ocean - exchange
We review important advances in our understanding of the global carbon cycle since the publication of the IPCC AR4. We conclude that: the anthropogenic emissions of CO2 due to fossil fuel burning have increased up through 2008 at a rate near to the high end of the IPCC emission scenarios; there are contradictory analyses whether an increase in atmospheric fraction, that might indicate a declining sink strength of ocean and/or land, exists; methane emissions are increasing, possibly through enhanced natural emission from northern wetland, methane emissions from dry plants are negligible; old-growth forest take up more carbon than expected from ecological equilibrium reasoning; tropical forest also take up more carbon than previously thought, however, for the global budget to balance, this would imply a smaller uptake in the northern forest; the exchange fluxes between the atmosphere and ocean are increasingly better understood and bottom up and observation-based top down estimates are getting closer to each other; the North Atlantic and Southern ocean take up less CO2, but it is unclear whether this is part of the ‘natural’ decadal scale variability; large-scale fires and droughts, for instance in Amazonia, but also at Northern latitudes, have lead to significant decreases in carbon uptake on annual timescales; the extra uptake of CO2 stimulated by increased N-deposition is, from a greenhouse gas forcing perspective, counterbalanced by the related additional N2O emissions; the amount of carbon stored in permafrost areas appears much (two times) larger than previously thought; preservation of existing marine ecosystems could require a CO2 stabilization as low as 450 ppm; Dynamic Vegetation Models show a wide divergence for future carbon trajectories, uncertainty in the process description, lack of understanding of the CO2 fertilization effect and nitrogen–carbon interaction are major uncertainties.
Inverse modeling of European CH4 emissions: sensitivity to the observational network
Villani, M.G. ; Bergamaschi, P. ; Krol, M.C. ; Meirink, J.F. ; Dentener, F. - \ 2010
Atmospheric Chemistry and Physics 10 (2010)3. - ISSN 1680-7316 - p. 1249 - 1267.
atmospheric methane - term variations - co2 inversions - frequency data - transport - chemistry - sinks - tm5 - oh
Inverse modeling is widely employed to provide “top-down” emission estimates using atmospheric measurements. Here, we analyze the dependence of derived CH4 emissions on the sampling frequency and density of the observational surface network, using the TM5-4DVAR inverse modeling system and synthetic observations. This sensitivity study focuses on Europe. The synthetic observations are created by TM5 forward model simulations. The inversions of these synthetic observations are performed using virtually no knowledge on the a priori spatial and temporal distribution of emissions, i.e. the emissions are derived mainly from the atmospheric signal detected by the measurement network. Using the European network of stations for which continuous or weekly flask measurements are available for 2001, the synthetic experiments can retrieve the “true” annual total emissions for single countries such as France within 20%, and for all North West European countries together within ~5%. However, larger deviations are obtained for South and East European countries due to the scarcity of stations in the measurement network. Upgrading flask sites to stations with continuous measurements leads to an improvement for central Europe in emission estimates. For realistic emission estimates over the whole European domain, however, a major extension of the number of stations in the existing network is required. We demonstrate the potential of an extended network of a total of ~60 European stations to provide realistic emission estimates over the whole European domain.
A Meta-Regression Analysis of Forest Carbon Offset Costs
Kooten, G.C. van; Laaksonen-Craig, S. ; Wang, Y. - \ 2009
Canadian Journal of Forest Research 39 (2009)11. - ISSN 0045-5067 - p. 2153 - 2167.
fossil-fuel substitution - sequestering carbon - accounting methods - agricultural land - western canada - climate-change - co2 storage - sequestration - sinks - metaanalysis
The main focus of efforts to mitigate climate change is on the avoidance of fossil fuel emissions. However, the Kyoto Protocol rules permit the use of forestry activities that create carbon offset credits. These could obviate the need for lifestyle-changing reductions in fossil fuel use. Therefore, it is necessary for policy purpose to determine the cost effectiveness of creating forest sink carbon credits. In this study, meta-regression analyses with 1047 observations from 68 studies are used to determine factors that affect carbon sequestration costs. Results indicate that forest plantations and use of harvested biomass for energy make forestry activities more attractive. It also turns out that forestry activities are competitive with emissions reduction in tropical regions and, perhaps, boreal regions but certainly not in Europe. Finally, the regression estimates are used to project the potential costs of carbon uptake for various forest management scenarios— costs range from 0 to over 200US$/t CO2. Le principal objectif des efforts visant à atténuer les changements climatiques consiste à éviter les émissions de combustibles fossiles. Cependant, les règles de le protocole de Kyoto permettent d'utiliser les activités forestières qui génèrent des crédits pour compenser les émissions de carbone, ce qui pourrait éviter de devoir réduire l'utilisation de combustibles fossiles qui entraînerait un changement de style de vie. Par conséquent, pour établir des politiques il est nécessaire de déterminer le rapport coût-efficacité de la création de crédits en utilisant la forêt comme puits de carbone. Dans cette étude, des analyses de méta-régression avec 1047 observations provenant de 68 études sont utilisées pour déterminer les facteurs qui influencent les coûts de séquestration du carbone. Les résultats indiquent que les plantations forestières et l'utilisation de la biomasse qui est récoltée pour produire de l'énergie rendent les activités forestières plus attrayantes. De plus, les activités forestières sont compétitives avec la réduction des émissions dans les régions tropicales et possiblement dans les régions boréales, mais certainement pas en Europe. Finalement, les estimations des régressions sont utilisées pour prédire le coût potentiel de la séquestration du carbone associé à différents scénarios d'aménagement forestier; les coûts varient de 0 à 200 $US par tonne de CO2.
TransCom model simulations of hourly atmospheric CO2: Analysis of synoptic-scale variations for the period 2002-2003
Patra, P.K. ; Law, R.M. ; Peters, W. ; Krol, M.C. - \ 2008
Global Biogeochemical Cycles 22 (2008). - ISSN 0886-6236 - 16
klimaatverandering - kooldioxide - emissie - simulatiemodellen - climatic change - carbon dioxide - emission - simulation models - carbon-dioxide - transport models - tall tower - inversions - sinks - variability - delta-c-13 - europe - trends - cycle
The ability to reliably estimate CO2 fluxes from current in situ atmospheric CO2 measurements and future satellite CO2 measurements is dependent on transport model performance at synoptic and shorter timescales. The TransCom continuous experiment was designed to evaluate the performance of forward transport model simulations at hourly, daily, and synoptic timescales, and we focus on the latter two in this paper. Twenty-five transport models or model variants submitted hourly time series of nine predetermined tracers (seven for CO2) at 280 locations. We extracted synoptic-scale variability from daily averaged CO2 time series using a digital filter and analyzed the results by comparing them to atmospheric measurements at 35 locations. The correlations between modeled and observed synoptic CO2 variabilities were almost always largest with zero time lag and statistically significant for most models and most locations. Generally, the model results using diurnally varying land fluxes were closer to the observations compared to those obtained using monthly mean or daily average fluxes, and winter was often better simulated than summer. Model results at higher spatial resolution compared better with observations, mostly because these models were able to sample closer to the measurement site location. The amplitude and correlation of model-data variability is strongly model and season dependent. Overall similarity in modeled synoptic CO2 variability suggests that the first-order transport mechanisms are fairly well parameterized in the models, and no clear distinction was found between the meteorological analyses in capturing the synoptic-scale dynamics.
Comparison of uncertainties in carbon sequestration estimates for a tropical and a temperate forest
Nabuurs, G.J. ; Putten, B. van; Knippers, T.S. ; Mohren, G.M.J. - \ 2008
Forest Ecology and Management 256 (2008)3. - ISSN 0378-1127 - p. 237 - 245.
management - stability - projects - finland - balance - sector - soils - sinks
We compare uncertainty through sensitivity and uncertainty analyses of the modelling framework CO2FIX V.2. We apply the analyses to a Central European managed Norway spruce stand and a secondary tropical forest in Central America. Based on literature and experience we use three standard groups to express uncertainty in the input parameters: 5%, 10% and 20%. Sensitivity analyses show that parameters exhibiting highest influence on carbon sequestration are carbon content, wood density and current annual increment of stems. Three main conclusions arise from this investigation: (1) parameters that largely determine model output are stem parameters, (2) depending on initial state of the model, perturbation can lead to multiple equilibrium, and (3) the standard deviation of total carbon stock is double in the tropical secondary forest for the wood density, and current annual increment. The standard deviation caused by uncertainty in mortality rate is more than 10-fold in the tropical forest case than in the temperate managed forest. Even in a case with good access to data, the uncertainty remains very high, much higher than what can reasonably be achieved in carbon sequestration through changes in forest management
Inverse Modeling Estimates of the Global Nitrous Oxide Surface Flux from 1998-2001
Hirsch, A. ; Michalak, A. ; Bruhwiler, L. ; Peters, W. ; Dlugokencky, E. ; Tans, P.P. - \ 2006
Global Biogeochemical Cycles 20 (2006)1. - ISSN 0886-6236 - 17 p.
atmospheric transport models - trace-gas emissions - european emissions - seasonal-variation - n2o emissions - co2 sources - costa-rica - sinks - exchange - soils
Measurements of nitrous oxide in air samples from 48 sites in the Cooperative Global Air Sampling Network made by NOAA/ESRL GMD CCGG (the Carbon Cycle Greenhouse Gases group in the Global Monitoring Division at the NOAA Earth System Research Laboratory in Boulder, Colorado) and the three-dimensional chemical transport model TM3 were used to infer global nitrous oxide fluxes and their uncertainties from 1998–2001. Results are presented for four semihemispherical regions (90°S–30°S, 30°S to equator, equator to 30°N, 30°N–90°N) and six broad “super regions” (Southern Land, Southern Oceans, Tropical Land, Tropical Oceans, Northern Land, and Northern Oceans). We found that compared to our a priori estimate (from the International Geosphere-Biosphere Programme's Global Emissions Inventory Activity), the a posteriori flux was much lower from 90°S–30°S and substantially higher from equator to 30°N. Consistent with these results, the a posteriori flux from the Southern Oceans region was lower than the a priori estimate, while Tropical Land and Tropical Ocean estimates were higher. The ratio of Northern Hemisphere to Southern Hemisphere fluxes was found to range from 1.9 to 5.2 (depending on the model setup), which is higher than the a priori ratio (1.5) and at the high end of previous estimates. Globally, ocean emissions contributed 26–36% of the total flux (again depending on the model setup), consistent with the a priori estimate (29%), though somewhat higher than some other previous estimates
An improved Kalman Smoother for atmospheric inversions
Bruhwiler, L. ; Michalak, A. ; Peters, W. ; Baker, D. ; Tans, P.P. - \ 2005
Atmospheric Chemistry and Physics 5 (2005). - ISSN 1680-7316 - p. 2691 - 2702.
carbon-dioxide - trace gases - co2 sources - transport - sensitivity - models - sinks - emissions - scheme - cycle
We explore the use of a fixed-lag Kalman smoother for sequential estimation of atmospheric carbon dioxide fluxes. This technique takes advantage of the fact that most of the information about the spatial distribution of sources and sinks is observable within a few months to half of a year of emission. After this period, the spatial structure of sources is diluted by transport and cannot significantly constrain flux estimates. We therefore describe an estimation technique that steps through the observations sequentially, using only the subset of observations and modeled transport fields that most strongly constrain the fluxes at a particular time step. Estimates of each set of fluxes are sequentially updated multiple times, using measurements taken at different times, and the estimates and their uncertainties are shown to quickly converge. Final flux estimates are incorporated into the background state of CO2 and transported forward in time, and the final flux uncertainties and covariances are taken into account when estimating the covariances of the fluxes still being estimated. The computational demands of this technique are greatly reduced in comparison to the standard Bayesian synthesis technique where all observations are used at once with transport fields spanning the entire period of the observations. It therefore becomes possible to solve larger inverse problems with more observations and for fluxes discretized at finer spatial scales. We also discuss the differences between running the inversion simultaneously with the transport model and running it entirely off-line with pre-calculated transport fields. We find that the latter can be done with minimal error if time series of transport fields of adequate length are pre-calculated.
Maximum likelihood estimation of covariance parameters for Bayesian atmospheric trace gas surface flux inversions
Michalak, A.M. ; Hirsch, A. ; Bruhwiler, L. ; Gurney, K.R. ; Peters, W. ; Tans, P.P. - \ 2005
Journal of Geophysical Research: Atmospheres 110 (2005)D24. - ISSN 2169-897X - 16 p.
carbon-dioxide - co2 inversions - transport - sinks - cycle - uncertainty - delta-c-13
This paper introduces a Maximum Likelihood (ML) approach for estimating the statistical parameters required for the covariance matrices used in the solution of Bayesian inverse problems aimed at estimating surface fluxes of atmospheric trace gases. The method offers an objective methodology for populating the covariance matrices required in Bayesian inversions, thereby resulting in better estimates of the uncertainty associated with derived fluxes and minimizing the risk of inversions being biased by unrealistic covariance parameters. In addition, a method is presented for estimating the uncertainty associated with these covariance parameters. The ML method is demonstrated using a typical inversion setup with 22 flux regions and 75 observation stations from the National Oceanic and Atmospheric Administration-Climate Monitoring and Diagnostics Laboratory (NOAA-CMDL) Cooperative Air Sampling Network with available monthly averaged carbon dioxide data. Flux regions and observation locations are binned according to various characteristics, and the variances of the model-data mismatch and of the errors associated with the a priori flux distribution are estimated from the available data
An ensemble data assimilation system to estimate CO2 surface fluxes from atmospheric trace gas observations
Peters, W. ; Miller, J.B. ; Whitaker, J. ; Denning, A.S. ; Hirsch, A. ; Krol, M.C. ; Zupanski, D. ; Bruhwiler, L. ; Tans, P.P. - \ 2005
Journal of Geophysical Research: Atmospheres 110 (2005). - ISSN 2169-897X - 18 p.
air-sampling-network - carbon-dioxide data - transport model - kalman filter - interannual variability - satellite-observations - inversion - emissions - sinks - cycle
We present a data assimilation system to estimate surface fluxes of CO2 and other trace gases from observations of their atmospheric abundances. The system is based on ensemble data assimilation methods under development for Numerical Weather Prediction (NWP) and is the first of its kind to be used for CO2 flux estimation. The system was developed to overcome computational limitations encountered when a large number of observations are used to estimate a large number of unknown surface fluxes. The ensemble data assimilation approach is attractive because it returns an approximation of the covariance, does not need an adjoint model or other linearization of the observation operator, and offers the possibility to optimize fluxes of chemically active trace gases (e.g., CH4, CO) in the same framework. We assess the performance of this new system in a pseudodata experiment that resembles the real problem we will apply this system to. The sensitivity of the method to the choice of several parameters such as the assimilation window size and the number of ensemble members is investigated. We conclude that the system is able to provide satisfactory flux estimates for the relatively large scales resolved by our current observing network and that the loss of information in the approximated covariances is an acceptable price to pay for the efficient computation of a large number of surface fluxes. The full potential of this data assimilation system will be used for near–real time operational estimates of North American CO2 fluxes. This will take advantage of the large amounts of atmospheric data that will be collected by NOAA-CMDL in conjunction with the implementation of the North American Carbon Program (NACP).
The Dutch N-cascade in the European perspective
Erisman, J.W. ; Domburg, N. ; Vries, W. de; Kros, H. ; Haan, B. de; Sanders, K. - \ 2005
Science in China Series C-Life Sciences 48 (2005)Spec Issue. - ISSN 1006-9305 - p. 827 - 842.
global nitrogen-cycle - terrestrial ecosystems - deposition - netherlands - consequences - forest - soils - fluxes - sinks - fate
The Netherlands is "well known" for its nitrogen problems; it has one of the highest reactive nitrogen (Nr) emission densities in the world. It is a small country at the delta of several large European rivers. Ever since the industrial revolution, there has been a growing excess of nutrients and related emissions into the atmosphere (ammonia, nitrogen oxides and nitrous oxide) and into groundwater and surface water (nitrate), leading to a large range of cascading environmental impacts. Vehicular traffic, sewage and animal husbandry are the main sources of oxidized and reduced forms of Nr. This paper provides an overview of the origin and fate of nitrogen in the Netherlands, the various reported impacts of nitrogen, the Dutch and European policies to reduce nitrogen emissions and related impacts. In addition, ways are presented to go forward to potentially solve the problems in a European perspective. Solutions include the improvement of nitrogen efficiencies in different systems, technological options and education.
Boreal Forest Carbon Sequestration Strategies : a Case Study of the Little Red River Cree First Nation Land Tenures
Krcmar, E. ; Kooten, G.C. van - \ 2005
Canadian Journal of Agricultural Economics 53 (2005)4. - ISSN 0008-3976 - p. 325 - 341.
fossil-fuel substitution - western canada - trees - economics - sinks - wood - cost
In this paper, creation of carbon offset and emission reduction credits are examined from the perspective of the Little Red River Cree Nation (LRRCN), a forest tenure holder in northern Alberta. Carbon credits are produced under three scenarios: (1) carbon uptake in forest ecosystems, with postharvest waste left on site; (2) carbon uptake in forests and products; and (3) carbon uptake in forests with harvested fiber used for energy production. A mathematical programming model is used to solve for the minimum prices that cause the LRRCN to include production of carbon credits in its forest management and post-harvest processing strategies. If LRRCN is paid according to its costs of creating carbon credits, it will opt to use fiber for forest products as this provides the greatest earning potential. If LRRCN faces a fixed price for carbon credits, it will produce fiber for generating electricity in lieu of coal as this strategy has the lowest average cost. However, when costs of feedstock transportation and construction of a power plant are taken into account, carbon uptake in biomass and forest products turn out to be more competitive.
Diverging incentives for afforestation from carbon sequestration: an economic analysis of the EU afforestation program in the south of Italy
Tassone, V.C. ; Wesseler, J.H.H. ; Nesci, F.S. - \ 2004
Forest Policy and Economics 6 (2004)6. - ISSN 1389-9341 - p. 567 - 578.
non-timber values - agricultural lands - western canada - forest - sinks
This study analyses the change in faustmannian age considering the social benefits due to carbon sequestration under the Regulation 2080/92, the subsidies provided by the afforestation program and investigates, from the social point of view, the profitability of afforesting agricultural land. The analysis refers to Calabria, a region situated in the south of Italy. Representative species are chosen for this study. The optimal harvesting age excluding social benefits varies between 32 and 40 years according to the species considered. When including social benefits, optimal harvesting age increases for a carbon price of 20 Euro/t to 34-44 years and is close to the one excluding them. The inclusion of subsidies to encourage afforestation shortens the optimal harvesting age to 17-20 years from the forest owner's point of view. Interestingly the provision of subsidies contributes to a substantial increase in social loss due to the differences in optimal harvesting ages: starting from zero C price the loss vary between 65 and 165 Euro/ha according to the species used and increases with rising carbon prices up to 200-400 Euro/ha for carbon price of 100 Euro/t. Furthermore, results suggest that from the social point of view the profitability of afforesting agricultural land in the study region very much depends on the price of carbon, on the type of agricultural land afforested and on the species used. (C) 2003 Elsevier B.V. All rights reserved.