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  • 1
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    The BETHY/JSBACH Carbon Cycle Data Assimilation System: experiences and challenges (2013)
    Wiley
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    Publication Date: 2013-09-18
    Description: [1]  We present the concept of the Carbon Cycle Data Assimilation System and describe its evolution over the last two decades from an assimilation system around a simple diagnostic model of the terrestrial biosphere to a system for the calibration and initialization of the land component of a comprehensive earth system model. We critically review the capability of this modeling framework to integrate multiple data streams, to assess their mutual consistency and with the model, to reduce uncertainties in the simulation of the terrestrial carbon cycle, to provide, in a traceable manner, reanalysis products with documented uncertainty, and to assist the design of the observational network. We highlight some of the challenges we met and experience we gained, give recommendations for operating the system and suggest directions for future development.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    An inter-comparison of inverse models for estimating sources and sinks of CO2 using GOSAT measurements (2015)
    Wiley
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    Publication Date: 2015-05-08
    Description: This study presents the outcome of an inverse modeling inter-comparison experiment on the use of total column CO 2 retrievals from GOSAT for quantifying global sources and sinks of CO 2 . Eight research groups submitted inverse modeling results for the first year of GOSAT measurements. Inversions were carried out using only GOSAT data, a combination of GOSAT and surface measurements, and using only surface measurements. As expected, the most robust flux estimates are obtained at large scales (e.g. within 20% of the annual flux at the global scale), and they quickly diverge towards the scale of the sub-continental TRANSCOM regions and beyond (to〉100% of the annual flux). We focus our analysis on a shift in the CO 2 uptake over land from the Tropics towards the Northern Hemisphere Extra tropics of ~1 PgC/yr when GOSAT data are used in the inversions. This shift is largely driven by TRANSCOM regions Europe and Northern Africa, showing, respectively, an increased uptake and release of 0.7 and 0.9 PgC/yr. Inversions using GOSAT data show a reduced gradient between mid latitudes of the Northern Hemisphere and the Tropics, consistent with the latitudinal shift in carbon uptake. However, the reduced gradients degrade the agreement with background aircraft and surface measurements. To narrow the range of inversion-derived flux estimates will require further efforts to understand the differences not only between the retrieval schemes but also between inverse models, as their contributions to the overall uncertainty are estimated to be of similar magnitude.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Global column-averaged methane mixing ratios from 2003 to 2009 as derived from SCIAMACHY: Trends and variability (2011)
    Wiley
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    Publication Date: 2011-02-17
    Description: After a decade of stable or slightly decreasing global methane concentrations, ground-based in situ data show that CH4 began increasing again in 2007 and that this increase continued through 2009. So far, space-based retrievals sensitive to the lower troposphere in the time period under consideration have not been available. Here we report a long-term data set of column-averaged methane mixing ratios retrieved from spectra of the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) instrument onboard Envisat. The retrieval quality after 2005 was severely affected by degrading detector pixels within the methane 2ν3 absorption band. We identified the most crucial problems in SCIAMACHY detector degradation and overcame the problem by applying a strict pixel mask as well as a new dark current characterization. Even though retrieval precision after the end of 2005 is invariably degraded, consistent methane retrievals from 2003 through 2009 are now possible. Regional time series in the Sahara, Australia, tropical Africa, South America, and Asia show the methane increase in 2007–2009, but we cannot yet draw a firm conclusion concerning the origin of the increase. Tropical Africa even seems to exhibit a negative anomaly in 2006, but an impact from changes in SCIAMACHY detector degradation cannot be excluded yet. Over Assakrem, Algeria, we observed strong similarities between SCIAMACHY measurements and ground-based data in deseasonalized time series. We further show long-term SCIAMACHY xCH4 averages at high spatial resolution that provide further insight into methane variations on regional scales. The Red Basin in China exhibits, on average, the highest methane abundance worldwide, while other localized features such as the Sudd wetlands in southern Sudan can also be identified in SCIAMACHY xCH4 averages.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 4
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    Large tundra methane burst during onset of freezing (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-12-05
    Description: Terrestrial wetland emissions are the largest single source of the greenhouse gas methane. Northern high-latitude wetlands contribute significantly to the overall methane emissions from wetlands, but the relative source distribution between tropical and high-latitude wetlands remains uncertain. As a result, not all the observed spatial and seasonal patterns of atmospheric methane concentrations can be satisfactorily explained, particularly for high northern latitudes. For example, a late-autumn shoulder is consistently observed in the seasonal cycles of atmospheric methane at high-latitude sites, but the sources responsible for these increased methane concentrations remain uncertain. Here we report a data set that extends hourly methane flux measurements from a high Arctic setting into the late autumn and early winter, during the onset of soil freezing. We find that emissions fall to a low steady level after the growing season but then increase significantly during the freeze-in period. The integral of emissions during the freeze-in period is approximately equal to the amount of methane emitted during the entire summer season. Three-dimensional atmospheric chemistry and transport model simulations of global atmospheric methane concentrations indicate that the observed early winter emission burst improves the agreement between the simulated seasonal cycle and atmospheric data from latitudes north of 60 degrees N. Our findings suggest that permafrost-associated freeze-in bursts of methane emissions from tundra regions could be an important and so far unrecognized component of the seasonal distribution of methane emissions from high latitudes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mastepanov, Mikhail -- Sigsgaard, Charlotte -- Dlugokencky, Edward J -- Houweling, Sander -- Strom, Lena -- Tamstorf, Mikkel P -- Christensen, Torben R -- England -- Nature. 2008 Dec 4;456(7222):628-30. doi: 10.1038/nature07464.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉GeoBiosphere Science Centre, Physical Geography and Ecosystems Analysis, Lund University, Solvegatan 12, 22362, Lund, Sweden.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19052625" target="_blank"〉PubMed〈/a〉
    Keywords: Arctic Regions ; Atmosphere/*chemistry ; Cold Climate ; *Freezing ; Greenland ; Methane/analysis/*metabolism ; Seasons ; Soil/analysis ; *Wetlands
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 5
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    Natural and anthropogenic variations in methane sources during the past two millennia (2012)
    Nature Publishing Group (NPG)
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    Publication Date: 2012-10-06
    Description: Methane is an important greenhouse gas that is emitted from multiple natural and anthropogenic sources. Atmospheric methane concentrations have varied on a number of timescales in the past, but what has caused these variations is not always well understood. The different sources and sinks of methane have specific isotopic signatures, and the isotopic composition of methane can therefore help to identify the environmental drivers of variations in atmospheric methane concentrations. Here we present high-resolution carbon isotope data (delta(13)C content) for methane from two ice cores from Greenland for the past two millennia. We find that the delta(13)C content underwent pronounced centennial-scale variations between 100 BC and AD 1600. With the help of two-box model calculations, we show that the centennial-scale variations in isotope ratios can be attributed to changes in pyrogenic and biogenic sources. We find correlations between these source changes and both natural climate variability--such as the Medieval Climate Anomaly and the Little Ice Age--and changes in human population and land use, such as the decline of the Roman empire and the Han dynasty, and the population expansion during the medieval period.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sapart, C J -- Monteil, G -- Prokopiou, M -- van de Wal, R S W -- Kaplan, J O -- Sperlich, P -- Krumhardt, K M -- van der Veen, C -- Houweling, S -- Krol, M C -- Blunier, T -- Sowers, T -- Martinerie, P -- Witrant, E -- Dahl-Jensen, D -- Rockmann, T -- England -- Nature. 2012 Oct 4;490(7418):85-8. doi: 10.1038/nature11461.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Princetonplein 5, 3584CC Utrecht, The Netherlands. c.j.sapart@uu.nl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23038470" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/chemistry ; Biomass ; Carbon Isotopes ; Climate Change/history ; Fires/*history ; Greenland ; History, 15th Century ; History, 16th Century ; History, 17th Century ; History, 18th Century ; History, 19th Century ; History, 20th Century ; History, Ancient ; History, Medieval ; Holy Roman Empire ; Human Activities/*history ; Ice/analysis ; Methane/analysis/*history/*metabolism ; Population Dynamics ; Roman World/history
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 6
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    Iconic CO2 time series at risk (2012)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2012-09-01
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Houweling, Sander -- Badawy, Bakr -- Baker, David F -- Basu, Sourish -- Belikov, Dmitry -- Bergamaschi, Peter -- Bousquet, Philippe -- Broquet, Gregoire -- Butler, Tim -- Canadell, Josep G -- Chen, Jing -- Chevallier, Frederic -- Ciais, Philippe -- Collatz, G James -- Denning, Scott -- Engelen, Richard -- Enting, Ian G -- Fischer, Marc L -- Fraser, Annemarie -- Gerbig, Christoph -- Gloor, Manuel -- Jacobson, Andrew R -- Jones, Dylan B A -- Heimann, Martin -- Khalil, Aslam -- Kaminski, Thomas -- Kasibhatla, Prasad S -- Krakauer, Nir Y -- Krol, Maarten -- Maki, Takashi -- Maksyutov, Shamil -- Manning, Andrew -- Meesters, Antoon -- Miller, John B -- Palmer, Paul I -- Patra, Prabir -- Peters, Wouter -- Peylin, Philippe -- Poussi, Zegbeu -- Prather, Michael J -- Randerson, James T -- Rockmann, Thomas -- Rodenbeck, Christian -- Sarmiento, Jorge L -- Schimel, David S -- Scholze, Marko -- Schuh, Andrew -- Suntharalingam, Parv -- Takahashi, Taro -- Turnbull, Jocelyn -- Yurganov, Leonid -- Vermeulen, Alex -- New York, N.Y. -- Science. 2012 Aug 31;337(6098):1038-40. doi: 10.1126/science.337.6098.1038-b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22936755" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/*chemistry ; Carbon Dioxide/*analysis ; *Climate Change
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Chemical feedback from decreasing carbon monoxide emissions (2017)
    Wiley
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    Publication Date: 2017-09-14
    Description: Understanding changes in the burden and growth rate of atmospheric methane (CH 4 ) has been the focus of several recent studies but still lacks scientific consensus. Here we investigate the role of decreasing anthropogenic carbon monoxide (CO) emissions since 2002 on hydroxyl radical (OH) sinks and tropospheric CH 4 loss. We quantify this impact by contrasting two model simulations for 2002-2013: 1) a MOPITT CO reanalysis, and 2) a Control-Run without CO assimilation. These simulations are performed with the CESM/CAM-Chem fully-coupled chemistry climate model with prescribed CH 4 surface concentrations. The assimilation of MOPITT observations constrains the global CO burden, which significantly decreased over this period by ~20%. We find that this decrease results to: a) increase in CO chemical production, b) higher CH 4 oxidation by OH, and c) ~8% shorter CH 4 lifetime. We elucidate this coupling by a surrogate mechanism for CO-OH-CH 4 that is quantified from the full chemistry simulations.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    US CH4 Emissions from Oil and Gas Production: Have Recent Large Increases Been Detected? (2017)
    Wiley
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    Publication Date: 2017-03-09
    Description: Recent studies have proposed significant increases in CH 4 emissions possibly from oil and gas (O&G) production, especially for the US where O&G production has reached historically high levels over the past decade [ US EIA , 2016; Turner et al. , 2016; Hausmann et al. , 2015; Franco et al. , 2016]. In this study, we show that an ensemble of time-dependent atmospheric inversions constrained by calibrated atmospheric observations of surface CH 4 mole fraction, with some including space-based retrievals of column average CH 4 mole fractions, suggests that North American CH 4 emissions have been flat over years spanning 2000 through 2012. Estimates of emission trends using zonal gradients of column average CH 4 calculated relative to an upstream background are not easy to make due to atmospheric variability, relative insensitivity of column average CH 4 to surface emissions at regional scales, and fast zonal synoptic transport. In addition, any trends in continental enhancements of column average CH 4 are sensitive to how the upstream background is chosen, and model simulations imply that short-term (4 years or less) trends in column average CH 4 horizontal gradients of up to 1.5 ppb/yr can occur just from inter-annual transport variability acting on a strong latitudinal CH 4 gradient. Finally, trends in spatial gradients calculated from space-based column average CH 4 can be significantly biased (〉2-3 ppb/yr) due to the non-uniform and seasonally varying temporal coverage of satellite retrievals.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Atmospheric CH4 in the first decade of the 21st century: Inverse modeling analysis using SCIAMACHY satellite retrievals and NOAA surface measurements (2013)
    Wiley
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    Publication Date: 2013-05-12
    Description: [1]  The causes of renewed growth in the atmospheric CH 4 burden since 2007 are still poorly understood and the subject of intensive scientific discussion. Here, we present a reanalysis of global CH 4 emissions during the 2000s, based on the TM5-4DVAR inverse modeling system. We use high-accuracy surface observations from the NOAA Earth System Research Laboratory global cooperative air sampling network for 2000–2010, together with retrievals of column-averaged CH 4 mole fractions from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument onboard ENVISAT from 2003 onwards. [2]  Using climatological OH fields, derived global total emissions for 2007–2010 are 16–20 Tg CH 4 /yr higher than for 2003–2005. Most of the inferred increase was located in the tropics (9–14 Tg CH 4 /yr) and mid-latitudes of the northern hemisphere (6–8 Tg CH 4 /yr), while no significant trend was derived for Arctic latitudes. The atmospheric increase can be attributed mainly to an increase of anthropogenic emissions. However, the derived trend in anthropogenic emissions is significantly smaller than the one estimated in the EDGARv4.2 emission inventory. Superimposed on the increasing trend in anthropogenic CH 4 emissions are significant inter-annual variations (IAV) of CH 4 emissions from wetlands (up to ±10 Tg CH 4 /yr), and biomass burning (up to ±7 Tg CH 4 /yr). [3]  Various sensitivity experiments have been performed to investigate the impact of the SCIAMACHY observations (compared to inversions using only surface observations), of the OH fields used, and of a priori emission inventories on the derived CH 4 emission trends and their inter-annual variability. Despite significant differences among these sensitivity experiments in their latitudinal attribution of IAV of CH 4 emissions, they show a reasonably consistent picture regarding the IAV aggregated on larger latitude bands. Furthermore, all sensitivity experiments show very similar performance against a comprehensive independent dataset of observations used for validation, including NOAA ship and aircraft profile samples, HIPPO aircraft transects, and CARIBIC aircraft data. Comparison of model simulations with BARCA aircraft measurements, however, show significantly better agreement in the free troposphere over the Amazon for the inversions using the SCIAMACHY and NOAA surface observations compared to inversions using only the surface observations, demonstrating the usefulness of the satellite measurements to better constrain tropical CH 4 emissions.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 10
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    Reduced carbon uptake during the 2010 Northern Hemisphere summer from GOSAT (2013)
    Wiley
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    Publication Date: 2013-03-26
    Description: [1]  Column-averaged dry air mole fractions of carbon dioxide (XCO 2 ) measured by the Greenhouse Gases Observing Satellite (GOSAT) reveal significant interannual variation (IAV) of CO 2 uptake during the Northern Hemisphere summer between 2009 and 2010. The XCO 2 drawdown in 2010 is shallower than in 2009 by 2.4 ppm and 3.0 ppm over North America and Eurasia, respectively. Reduced carbon uptake in the summer of 2010 is most likely due to the heat wave in Eurasia driving biospheric fluxes and fire emissions. A joint inversion of GOSAT and surface data estimates an integrated biospheric and fire emission anomaly in April–September of 0.89 ± 0.20 PgC over Eurasia. In contrast, inversions of surface measurements alone fail to replicate the observed XCO 2 IAV and underestimate emission IAV over Eurasia. This shows the value of GOSAT XCO 2 in constraining the response of land-atmosphere exchange of CO 2 to climate events.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
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