{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T16:40:40Z","timestamp":1772815240559,"version":"3.50.1"},"reference-count":40,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2019,4,9]],"date-time":"2019-04-09T00:00:00Z","timestamp":1554768000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002341","name":"Academy of Finland","doi-asserted-by":"publisher","award":["312125"],"award-info":[{"award-number":["312125"]}],"id":[{"id":"10.13039\/501100002341","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002341","name":"Academy of Finland","doi-asserted-by":"publisher","award":["303876"],"award-info":[{"award-number":["303876"]}],"id":[{"id":"10.13039\/501100002341","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000844","name":"European Space Agency","doi-asserted-by":"publisher","award":["DACES project"],"award-info":[{"award-number":["DACES project"]}],"id":[{"id":"10.13039\/501100000844","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>NASA\u2019s carbon dioxide mission, Orbiting Carbon Observatory-2, began operating in September 2014. In this paper, we analyze four years (2015\u20132018) of global (60\u00b0S\u201360\u00b0N) XCO2 anomalies and their annual variations and seasonal patterns. We show that the anomaly patterns in the column-averaged CO2 dry air mole fraction, XCO2, are robust and consistent from year-to-year. We evaluate the method by comparing the anomalies to fluxes from anthropogenic, biospheric, and biomass burning and to model-simulated local concentration enhancements. We find that, despite the simplicity of the method, the anomalies describe the spatio-temporal variability of XCO2 (including anthropogenic emissions and seasonal variability related to vegetation and biomass burning) consistently with more complex model-based approaches. We see, for example, that positive anomalies correspond to fossil fuel combustion over the major industrial areas (e.g., China, eastern USA, central Europe, India, and the Highveld region in South Africa), shown as large positive XCO2 enhancements in the model simulations. We also find corresponding positive anomalies and fluxes over biomass burning areas during different fire seasons. On the other hand, the largest negative anomalies correspond to the growing season in the northern middle latitudes, characterized by negative XCO2 enhancements from simulations and high solar-induced chlorophyll fluorescence (SIF) values (indicating the occurrence of photosynthesis). The largest discrepancies between the anomaly patterns and the model-based results are observed in the tropical regions, where OCO-2 shows persistent positive anomalies over every season of every year included in this study. Finally, we demonstrate how XCO2 anomalies enable the detection of anthropogenic signatures for several local scale case studies, both in the Northern and Southern Hemisphere. In particular, we analyze the XCO2 anomalies collocated with the recent TROPOspheric Monitoring Instrument NO2 observations (used as indicator of anthropogenic fossil fuel combustion) over the Highveld region in South Africa. The results highlight the capability of satellite-based observations to monitor natural and man-made CO2 signatures on global scale.<\/jats:p>","DOI":"10.3390\/rs11070850","type":"journal-article","created":{"date-parts":[[2019,4,9]],"date-time":"2019-04-09T05:58:07Z","timestamp":1554789487000},"page":"850","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":84,"title":["Analysis of Four Years of Global XCO2 Anomalies as Seen by Orbiting Carbon Observatory-2"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5281-8985","authenticated-orcid":false,"given":"Janne","family":"Hakkarainen","sequence":"first","affiliation":[{"name":"Finnish Meteorological Institute, 00560 Helsinki, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1125-0756","authenticated-orcid":false,"given":"Iolanda","family":"Ialongo","sequence":"additional","affiliation":[{"name":"Finnish Meteorological Institute, 00560 Helsinki, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1200-9577","authenticated-orcid":false,"given":"Shamil","family":"Maksyutov","sequence":"additional","affiliation":[{"name":"Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba 305-0053, Japan"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4573-9998","authenticated-orcid":false,"given":"David","family":"Crisp","sequence":"additional","affiliation":[{"name":"Jet Propulsion Laboratory\/California Institute of Technology, Pasadena, CA 91109, USA"}]}],"member":"1968","published-online":{"date-parts":[[2019,4,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"549","DOI":"10.5194\/amt-10-549-2017","article-title":"The Orbiting Carbon Observatory-2: First 18 months of science data products","volume":"10","author":"Eldering","year":"2017","journal-title":"Atmos. Meas. Tech."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Eldering, A., Wennberg, P.O., Crisp, D., Schimel, D.S., Gunson, M.R., Chatterjee, A., Liu, J., Schwandner, F.M., Sun, Y., and O\u2019Dell, C.W. (2017). The Orbiting Carbon Observatory-2 early science investigations of regional carbon dioxide fluxes. Science, 358.","DOI":"10.1126\/science.aam5745"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"5673","DOI":"10.5194\/amt-11-5673-2018","article-title":"Quantifying methane point sources from fine-scale satellite observations of atmospheric methane plumes","volume":"11","author":"Varon","year":"2018","journal-title":"Atmos. Meas. Tech."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Chevallier, F., Br\u00e9on, F.M., and Rayner, P.J. (2007). Contribution of the Orbiting Carbon Observatory to the estimation of CO2 sources and sinks: Theoretical study in a variational data assimilation framework. J. Geophys. Res. Atmos., 112.","DOI":"10.1029\/2006JD007375"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Miller, C.E., Crisp, D., DeCola, P.L., Olsen, S.C., Randerson, J.T., Michalak, A.M., Alkhaled, A., Rayner, P., Jacob, D.J., and Suntharalingam, P. (2007). Precision requirements for space-based data. J. Geophys. Res. Atmos., 112.","DOI":"10.1029\/2006JD007659"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"445","DOI":"10.1016\/0094-5765(94)00278-T","article-title":"SCIAMACHY\u2014Scanning imaging absorption spectrometer for atmospheric chartography","volume":"35","author":"Burrows","year":"1995","journal-title":"Acta Astronaut."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"160","DOI":"10.2151\/sola.2009-041","article-title":"Global Concentrations of CO2 and CH4 Retrieved from GOSAT: First Preliminary Results","volume":"5","author":"Yokota","year":"2009","journal-title":"SOLA"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"59","DOI":"10.5194\/amt-10-59-2017","article-title":"The on-orbit performance of the Orbiting Carbon Observatory-2 (OCO-2) instrument and its radiometrically calibrated products","volume":"10","author":"Crisp","year":"2017","journal-title":"Atmos. Meas. Tech."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"621","DOI":"10.1007\/s00376-018-7312-6","article-title":"First Global Carbon Dioxide Maps Produced from TanSat Measurements","volume":"35","author":"Yang","year":"2018","journal-title":"Adv. Atmos. Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1919","DOI":"10.1007\/s11430-013-4707-1","article-title":"Analysis of CO2 retrieval sensitivity using simulated Chinese Carbon Satellite (TanSat) measurements","volume":"57","author":"Cai","year":"2014","journal-title":"Sci. China Earth Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"10045","DOI":"10.1002\/2017GL074702","article-title":"Quantifying CO2 Emissions From Individual Power Plants From Space","volume":"44","author":"Nassar","year":"2017","journal-title":"Geophys. Res. Lett."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"792","DOI":"10.1038\/ngeo2257","article-title":"Decreasing emissions of NOx relative to CO2 in East Asia inferred from satellite observations","volume":"7","author":"Reuter","year":"2014","journal-title":"Nat. Geosci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"3486","DOI":"10.1002\/2016GL067843","article-title":"Comparing GOSAT observations of localized CO2 enhancements by large emitters with inventory-based estimates","volume":"43","author":"Janardanan","year":"2016","journal-title":"Geophys. Res. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Kort, E.A., Frankenberg, C., Miller, C.E., and Oda, T. (2012). Space-based observations of megacity carbon dioxide. Geophys. Res. Lett., 39.","DOI":"10.1029\/2012GL052738"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Schwandner, F.M., Gunson, M.R., Miller, C.E., Carn, S.A., Eldering, A., Krings, T., Verhulst, K.R., Schimel, D.S., Nguyen, H.M., and Crisp, D. (2017). Spaceborne detection of localized carbon dioxide sources. Science, 358.","DOI":"10.1126\/science.aam5782"},{"key":"ref_16","first-page":"1","article-title":"Constraining fossil fuel CO2 emissions from urban area using OCO-2 observations of total column CO2","volume":"2017","author":"Ye","year":"2017","journal-title":"Atmos. Chem. Phys. Discuss."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"9462","DOI":"10.1029\/2018JD029005","article-title":"Distinguishing anthropogenic CO2 emissions from different energy intensive industrial sources using OCO-2 observations: A case study in northern China","volume":"123","author":"Wang","year":"2018","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"2209","DOI":"10.5194\/amt-10-2209-2017","article-title":"Comparisons of the Orbiting Carbon Observatory-2 (OCO-2) XCO2 measurements with TCCON","volume":"10","author":"Wunch","year":"2017","journal-title":"Atmos. Meas. Tech."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Liu, J., Bowman, K.W., Schimel, D.S., Parazoo, N.C., Jiang, Z., Lee, M., Bloom, A.A., Wunch, D., Frankenberg, C., and Sun, Y. (2017). Contrasting carbon cycle responses of the tropical continents to the 2015\u20132016 El Ni\u00f1o. Science, 358.","DOI":"10.1126\/science.aam5690"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"5253","DOI":"10.1002\/2014JD022962","article-title":"An intercomparison of inverse models for estimating sources and sinks of CO2 using GOSAT measurements","volume":"120","author":"Houweling","year":"2015","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"11400","DOI":"10.1002\/2016GL070885","article-title":"Direct space-based observations of anthropogenic CO2 emission areas from OCO-2","volume":"43","author":"Hakkarainen","year":"2016","journal-title":"Geophys. Res. Lett."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"6539","DOI":"10.5194\/amt-11-6539-2018","article-title":"Improved retrievals of carbon dioxide from Orbiting Carbon Observatory-2 with the version 8 ACOS algorithm","volume":"11","author":"Eldering","year":"2018","journal-title":"Atmos. Meas. Tech."},{"key":"ref_23","first-page":"1","article-title":"How bias correction goes wrong: Measurement of XCO2 affected by erroneous surface pressure estimates","volume":"2018","author":"Kiel","year":"2018","journal-title":"Atmos. Meas. Tech. Discuss."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"18925","DOI":"10.1073\/pnas.0708986104","article-title":"An atmospheric perspective on North American carbon dioxide exchange: CarbonTracker","volume":"104","author":"Peters","year":"2007","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.rse.2014.02.007","article-title":"Prospects for chlorophyll fluorescence remote sensing from the Orbiting Carbon Observatory-2","volume":"147","author":"Frankenberg","year":"2014","journal-title":"Remote Sens. Environ."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Sun, Y., Frankenberg, C., Wood, J.D., Schimel, D.S., Jung, M., Guanter, L., Drewry, D.T., Verma, M., Porcar-Castell, A., and Griffis, T.J. (2017). OCO-2 advances photosynthesis observation from space via solar-induced chlorophyll fluorescence. Science, 358.","DOI":"10.1126\/science.aam5747"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2461","DOI":"10.5194\/acp-5-2461-2005","article-title":"Technical note: The Lagrangian particle dispersion model FLEXPART version 6.2","volume":"5","author":"Stohl","year":"2005","journal-title":"Atmos. Chem. Phys."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"87","DOI":"10.5194\/essd-10-87-2018","article-title":"The Open-source Data Inventory for Anthropogenic CO2, version 2016 (ODIAC2016): A global monthly fossil fuel CO2 gridded emissions data product for tracer transport simulations and surface flux inversions","volume":"10","author":"Oda","year":"2018","journal-title":"Earth Syst. Sci. Data"},{"key":"ref_29","unstructured":"Eskes, H., van Geffen, J., Boersma, F., Eichmann, K.U., Apituley, A., Pedergnana, M., Sneep, M., Veefkind, J.P., and Loyola, D. (2018). Sentinel-5 precursor\/TROPOMI Level 2 Product User Manual Nitrogendioxide."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"70","DOI":"10.1016\/j.rse.2011.09.027","article-title":"TROPOMI on the ESA Sentinel-5 Precursor: A GMES mission for global observations of the atmospheric composition for climate, air quality and ozone layer applications","volume":"120","author":"Veefkind","year":"2012","journal-title":"Remote Sens. Environ."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"2141","DOI":"10.5194\/essd-10-2141-2018","article-title":"Global Carbon Budget 2018","volume":"10","author":"Andrew","year":"2018","journal-title":"Earth Syst. Sci. Data"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"555","DOI":"10.1034\/j.1600-0889.2003.00049.x","article-title":"TransCom 3 CO2 inversion intercomparison: 1. Annual mean control results and sensitivity to transport and prior flux information","volume":"55","author":"Gurney","year":"2003","journal-title":"Tellus B"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"690","DOI":"10.1038\/ngeo2493","article-title":"Rapid increases in tropospheric ozone production and export from China","volume":"8","author":"Verstraeten","year":"2015","journal-title":"Nat. Geosci."},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Lin, M., Fiore, A.M., Horowitz, L.W., Cooper, O.R., Naik, V., Holloway, J., Johnson, B.J., Middlebrook, A.M., Oltmans, S.J., and Pollack, I.B. (2012). Transport of Asian ozone pollution into surface air over the western United States in spring. J. Geophys. Res. Atmos., 117.","DOI":"10.1029\/2011JD016961"},{"key":"ref_35","unstructured":"Bergamaschi, P., Danila, A., Weiss, R.F., Ciais, P., Thompson, R.L., Brunner, D., Levin, I., Meijer, Y., Chevallier, F., and Janssens-Maenhout, G. (2018). Atmospheric Monitoring and Inverse Modelling for Verification of gReenhouse Gas Inventories, Publications Office of the European Union."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1737","DOI":"10.1126\/science.1207824","article-title":"Megacity Emissions and Lifetimes of Nitrogen Oxides Probed from Space","volume":"333","author":"Beirle","year":"2011","journal-title":"Science"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"11497","DOI":"10.5194\/acp-16-11497-2016","article-title":"A global catalogue of large SO2 sources and emissions derived from the Ozone Monitoring Instrument","volume":"16","author":"Fioletov","year":"2016","journal-title":"Atmos. Chem. Phys."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"230","DOI":"10.1126\/science.aam5962","article-title":"Tropical forests are a net carbon source based on aboveground measurements of gain and loss","volume":"358","author":"Baccini","year":"2017","journal-title":"Science"},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Hansen, M.C., Potapov, P., and Tyukavina, A. (2019). Comment on \u201cTropical forests are a net carbon source based on aboveground measurements of gain and loss\u201d. Science, 363.","DOI":"10.1126\/science.aar3629"},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Pugh, T.A.M., Lindeskog, M., Smith, B., Poulter, B., Arneth, A., Haverd, V., and Calle, L. (2019). Role of forest regrowth in global carbon sink dynamics. Proc. Natl. Acad. Sci. USA.","DOI":"10.1073\/pnas.1810512116"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/7\/850\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:43:50Z","timestamp":1760186630000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/7\/850"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,4,9]]},"references-count":40,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2019,4]]}},"alternative-id":["rs11070850"],"URL":"https:\/\/doi.org\/10.3390\/rs11070850","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,4,9]]}}}