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Published February 21, 2020 | Supplemental Material + Published
Journal Article Open

Evidence of Carbon Uptake Associated with Vegetation Greening Trends in Eastern China

Abstract

Persistent and widespread increase of vegetation cover, identified as greening, has been observed in areas of the planet over late 20th century and early 21st century by satellite-derived vegetation indices. It is difficult to verify whether these regions are net carbon sinks or sources by studying vegetation indices alone. In this study, we investigate greening trends in Eastern China (EC) and corresponding trends in atmospheric CO₂ concentrations. We used multiple vegetation indices including NDVI and EVI to characterize changes in vegetation activity over EC from 2003 to 2016. Gap-filled time series of column-averaged CO₂ dry air mole fraction (XCO₂) from January 2003 to May 2016, based on observations from SCIAMACHY, GOSAT, and OCO-2 satellites, were used to calculate XCO₂ changes during growing season for 13 years. We derived a relationship between XCO₂ and surface net CO₂ fluxes from two inversion model simulations, CarbonTracker and Monitoring Atmospheric Composition and Climate (MACC), and used those relationships to estimate the biospheric CO₂ flux enhancement based on satellite observed XCO₂ changes. We observed significant growing period (GP) greening trends in NDVI and EVI related to cropland intensification and forest growth in the region. After removing the influence of large urban center CO₂ emissions, we estimated an enhanced XCO₂ drawdown during the GP of −0.070 to −0.084 ppm yr⁻¹. Increased carbon uptake during the GP was estimated to be 28.41 to 46.04 Tg C, mainly from land management, which could offset about 2–3% of EC's annual fossil fuel emissions. These results show the potential of using multi-satellite observed XCO₂ to estimate carbon fluxes from the regional biosphere, which could be used to verify natural sinks included as national contributions of greenhouse gas emissions reduction in international climate change agreements like the UNFCC Paris Accord.

Additional Information

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Received: 24 December 2019; Accepted: 19 February 2020; Published: 21 February 2020. We thank Prabir Patra for productive conversations regarding this analysis. We also thank ESA for sharing the SCIAMACHY BESD XCO2 level 2 data, the ACOS/OCO-2 project at JPL for sharing ACOS-GOSAT v7.3 and OCO-2 v7r data, NOAA ESRL for proving CarbonTracker CT2017 results, and ECMWF for providing MACC-III results. We thank NASA, NOAA, and Google Earth Engine for providing vegetation indices. Funding: This research was funded by the Key Research Program of Chinese Academy of Sciences (ZDRW-ZS-2019-3), the National Key Research and Development Program of China (2016YFA0600303) and the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA19080303). Z.H. was supported by a University of Chinese Academy of Sciences (UCAS) Joint PhD Program scholarship. Author Contributions: Conceptualization, L.R.W. and Z.H.; methodology, L.R.W. and Z.H.; formal analysis, L.R.W., Z.H. and L.L.; software, L.L., Z.-C.Z., and M.S.; writing—original draft preparation, Z.H. and L.R.W.; writing—review and editing, L.R.W., Z.H. and L.L. All authors have read and agreed to the published version of the manuscript. The authors declare no conflict of interest.

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Additional details

Created:
August 22, 2023
Modified:
October 19, 2023