Short-term reduction of regional enhancement of atmospheric CO2 in China during the first COVID-19 pandemic period

Abstract

Recent studies have reported a 9% decrease in global carbon emissions during the COVID-19 lockdown period; however, its impact on the variation of atmospheric CO _2 level remains under question. Using atmospheric CO _2 observed at Anmyeondo station (AMY) in South Korea, downstream of China, this study examines whether the decrease in China’s emissions due to COVID-19 can be detected from the enhancement of CO _2 mole fraction (ΔCO _2 ) relative to the background value. The Weather Research and Forecasting–Stochastic Time-Inverted Lagrangian Transport model was applied to determine when the observed mole fractions at AMY were affected by air parcels from China. Atmospheric observations at AMY showed up to a −20% (−1.92 ppm) decrease in ΔCO _2 between February and March 2020 compared to the same period in 2018 and 2019, particularly with a −34% (−3.61 ppm) decrease in March. ΔCO, which was analyzed to explore the short-term effect of emission reductions, had a decrease of −43% (−80.66 ppb) during the lockdown in China. Particularly in East China, where emissions are more concentrated than in Northeast China, ΔCO _2 and ΔCO decreased by −44% and −65%, respectively. The ΔCO/ΔCO _2 ratio (24.8 ppb ppm ^−1 ), which is the indicator of emission characteristics, did not show a significant difference before and after the COVID-19 lockdown period ( α = 0.05), suggesting that this decrease in ΔCO _2 and ΔCO was associated with emission reductions rather than changes in emission sources or combustion efficiency in China. Reduced carbon emissions due to limited human activity resulted in a decrease in the short-term regional enhancement to the observed atmospheric CO _2 .

Keywords

• COVID-19
• lockdown
• carbon dioxide
• atmospheric reduction
• WRF-STILT
• China