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Newswise – Monitoring anthropogenic greenhouse gas emissions using atmospheric observations is a major policy-making challenge, such as the Paris Agreement. Huge atmospheric observation networks consisting of a variety of platforms including satellites have been developed to monitor regional / national scale changes in anthropogenic greenhouse gas emissions. The outbreak of the novel coronavirus (COVID-19) affected global socioeconomic activity, leading to a significant reduction in CO2 emissions from fossil fuels (FFCO2) and other anthropogenic air pollutants around the world. This situation gave us a unique opportunity to assess our ability to quantify changes in regional FFCO2 emissions using atmospheric observations. However, there are few observational evidence reports for the reduction of CO2 emissions due to the COVID-19 blockade, although a large number of publications have reported short-lived reductions in air pollutants from various parts of the world.
In Scientific reports of Nature Publishing, researchers from the National Institute for Environmental Studies (NIES), Japan, and the Japanese Agency for Marine-Terrestrial Science and Technology (JAMSTEC) analyzed the atmospheric concentrations of CO2 and CH4 observed at Hateruma Island, Japan, East Asian continental margin and detected signs of FFCO2 reduction in China caused by the restrictions associated with the COVID-19 outbreak in January-March 2020.
We have estimated that FFCO2 emissions decreased by around 20% in the period January-February 2020 as a result of measures to prevent the spread of COVID-19 in China and the outside world. Although a significant reduction in air pollutants has been reported, documents on atmospheric signals of FFCO2 reduction have yet to be found in the published literature. “The size of the atmospheric CO2 reservoir is quite large and the atmospheric CO2 has a relatively long lifespan. These characteristics make the change in atmospheric CO2 concentrations caused by the COVID-19 flu rather small,” said Prabir K. Patra, co. -author of the study and researcher at JAMSTEC.
To detect such weak signals in CO2 changes, the NIES and JAMSTEC research team focused on the relative change in atmospheric CO2 and CH4 observed at Hateruma Island over the past 20 years at daily time intervals. “The atmospheric observation at Hateruma Island is often affected by continental emissions during the winter due to the pattern of airflow caused by the East Asian monsoon. We know that temporal variations in atmospheric concentrations of CO2 and CH4 show considerable similarity, and the temporal change in the relationship between CO2 and CH4 changes very well tracks the temporal change of fossil fuel emissions in China for the years before 2020, “said Yasunori Tohjima, lead author of the study and NIES researcher. . “Therefore, the change ratio between CO2 and CH4 was expected to detect the signal reflecting the change in continental CO2 emissions related to COVID-19 restrictions.”
The research team found that the monthly average ratio of changes in atmospheric CO2 to CH4 in January, February and March tracked the annual increase in FFCO2 emissions from China over the period 1997-2019. However, reports showed significant reductions in February and March 2020, which coincided with the lockdown period in China. “The relationship between the variation ratio and FFCO2 emissions from China should be evaluated using an atmospheric transport model and a set of CO2 and CH4 flux maps,” said Yosuke Niwa, study co-author and NIES researcher. “We used multiple simulations of atmospheric CO2 and CH4 at Hateruma Island for various scenarios for reducing CO2 emissions from fossil fuels using NICAM-TM.” The study therefore concluded that China’s FFCO2 emissions decreased by about 30% in February and by about 20% in March 2020. “Our approach presented in this study has the potential to detect signs of emissions reductions from any specific region in near real time using continuous and high-precision measurements of CO2 and CH4, “quoted Prabir K. Patra.
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