A241-02
Changes in the carbon dioxide column averages across the world during the first months of 2020

Wednesday, 16 December 2020: 11:34
Virtual
Frederic Chevallier1, Bo Zheng1, Gregoire Broquet1, Philippe Ciais2, Zhu Liu3, Steven J Davis4, Zhu Deng5, Yilong Wang6 and Christopher O'Dell7, (1)LSCE Laboratoire des Sciences du Climat et de l'Environnement, Gif-Sur-Yvette Cedex, France, (2)LSCE Laboratoire des Sciences du Climat et de l'Environnement, Gif-Sur-Yvette, France, (3)Tsinghua University, Department of Earth System Science, Beijing, China, (4)University of California Irvine, Department of Earth System Science, Irvine, CA, United States, (5)Department of Earth System Science, Tsinghua University, Beijing, China, (6)Institute of Geographical Sciences and Natural Resources Research, Beijing, China, (7)Colorado State University, Fort Collins, CO, United States
Recorded Presentation
Abstract:
The first half of 2020 represents an extreme period for the carbon cycle with both exceptionally high temperatures around the world and exceptionally low carbon dioxide (CO2) emissions associated with the use of fossil fuels. Various measurement systems that observe CO2 in the atmosphere have witnessed these changes, but despite different variability in space and time, separating natural and anthropogenic changes in observed concentrations remains difficult. Here, we study the changes in the column-average dry air-mole fraction of CO2 (XCO2) retrieved from the Second Orbiting Carbon Observatory (OCO-2) from January to May 2020.

To analyze changes due to natural fluxes, we use a global atmospheric inversion system that assimilated the full OCO-2 record, while prescribing fossil fuel fluxes based on activity data related to fossil fuel use. We show the anomaly of the carbon fluxes of terrestrial vegetation, linked in particular to an early start of the growing season in the northern hemisphere, by comparing the fluxes within the six years of the instrument.

To analyze the changes in XCO2 due to the use of fossil fuels, our starting point is a global simulation of the transport of CO2 in the atmosphere which allows us to estimate the order of magnitude and the location of the XCO2 signal induced by Covid-19. Our simulation indicates that the corresponding change in XCO2 is substantial in a few places, but is generally less than the uncertainty in the calibration of the retrievals. In addition, the main impact on XCO2 relates to areas that are poorly represented in quality-assured XCO2 retrievals from OCO-2. We then examine the local enhancements in XCO2 retrievals near isolated clusters of emissions in China, Europe, India and the USA: we remove the imprint of surface fluxes in their environment before we estimate the emission of these isolated clusters.

Based on the ability of the current OCO-2 system to pinpoint the extreme features of the carbon cycle in the first half of 2020, we will reassess user needs for future XCO2 observing systems, especially for monitoring anthropogenic emissions.

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