Local Anomalies in the Column‐Averaged Dry Air Mole Fractions of Carbon Dioxide Across the Globe During the First Months of the Coronavirus Recession

Abstract

We use a global transport model and satellite retrievals of the carbon dioxide (CO 2) column average to explore the impact of CO 2 emissions reductions that occurred during the economic downturn at the start of the Covid-19 pandemic. The changes in the column averages are substantial in a few places of the model global grid, but the induced gradients are most often less than the random errors of the retrievals. The current necessity to restrict the quality-assured column retrievals to almost cloud-free areas appears to be a major obstacle in identifying changes in CO 2 emissions. Indeed, large changes have occurred in the presence of clouds, and in places that were cloud free in 2020, the comparison with previous years is hampered by different cloud conditions during these years. We therefore recommend to favor all-weather CO 2 monitoring systems, at least in situ, to support international efforts to reduce emissions. Plain Language Summary The first half of 2020 represents an extreme period for the global carbon cycle with both exceptionally low carbon dioxide emissions from the use of fossil fuels and exceptionally high temperatures around the world. Here, we study the changes in human emissions witnessed from space by NASA's second Orbiting Carbon Observatory (OCO-2) from February to May 2020. We then reassess user needs for future carbon-dioxide observing systems that will monitor human emissions.

Can a regional-scale reduction of atmospheric CO<sub>2</sub> during the COVID-19 pandemic be detected from space? A case study for East China using satellite XCO<sub>2</sub> retrievals

“…CO 2 has many natural and anthropogenic sources and sinks, and our current understanding of them has significant gaps (e.g. Ciais et al, 2014;Chevallier et al, 2014;Reuter et al, 2017c;Friedlingstein et al, 2019). Efforts are ongoing to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes and to verify the effectiveness of policies such as the Paris Agreement (https://unfccc.int/process-and-meetings/ the-paris-agreement/the-paris-agreement, last access: 8 September 2020) aiming to reduce greenhouse gas emissions (e.g.…”

“…Efforts are ongoing to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes and to verify the effectiveness of policies such as the Paris Agreement (https://unfccc.int/process-and-meetings/ the-paris-agreement/the-paris-agreement, last access: 8 September 2020) aiming to reduce greenhouse gas emissions (e.g. Ciais et al, 2014Ciais et al, , 2015Pinty et al, 2017Pinty et al, , 2019Matsunaga and Maksyutov, 2018;Janssens-Maenhout et al, 2020).…”

Drought analysis with different indices for the Asi Basin (Turkey)

“…Many researchers discussed the drought situation combining with weather/climate conditions, such as severe weather occurrence frequency 3 – 8 .…”

Changes in China's anthropogenic emissions during the COVID-19 pandemic

“…These new approaches extrapolated the emission inventories of a baseline year to the current time in 2020 based on observational constraints or relevant activity indicators. The observation-based method ("top-down method") employed air pollutant concentrations measured by satellites (Chevallier et al, 2020;Miyazaki et al, 2020;Zhang et al, 2020;Zhang et al, 2021;Zheng et al, 2020) and ground stations (Feng et al, 2020;Xing et al, 2020) to infer the evolution of surface emissions, which are constrained by both observational data and chemical transport models. Satellite imagery of nitrogen dioxide (NO2) is widely used to constrain nitrogen oxide (NO x ) emissions due to its broad spatial coverage and high retrieval accuracy.…”