Tokyo, Nov 8 : The Covid-19 pandemic has been affecting the global socio-economic activity, leading to a significant reduction in fossil-fuel-derived CO2 (FFCO2) emissions and other anthropogenic air pollutants in the world, say researchers, including one of Indian-origin. This situation gave a unique opportunity to assess the ability to quantify the changes in the regional FFCO2 emissions using atmospheric observations, the study, published in the journal Scientific Reports, said. However, there are few reports of observational evidence for CO2 emission reduction due to the Covid-19 lockdown, although a large number of publications have reported reductions in short-lived air pollutants from various parts of the world. In the study, the research team analysed atmospheric CO2 and CH4 concentrations observed at Hateruma Island, Japan, and detected signals related to the FFCO2 reduction in China caused by the restrictions associated with the Covid-19 outbreak in January-March 2020. "We estimated that the FFCO2 emissions decreased by about 20 per cent during January-February 2020 as a result of the measures to prevent the spread of Covid-19 within China and to the outside world," said study author Prabir K. Patra from Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in Japan. While a significant reduction of the atmospheric pollutants has been reported, papers on the atmospheric signals of the FFCO2 reduction are yet to be found in the published literature. "The size of the atmospheric reservoir of CO2 is quite large and the atmospheric CO2 has a relatively long lifetime. These characteristics make the change in the atmospheric CO2 concentrations caused by the Covid-19 influence quite small," Patra added. To detect such faint signals in the CO2 variations, the research team focused on the relative variation of the atmospheric CO2 and CH4 observed at Hateruma Island for the past 20 years at daily time intervals. The research team found that the monthly average ratio of the atmospheric CO2 to CH4 variations in January, February, and March tracked the yearly increase in FFCO2 emissions from China during 1997-2019. However, the ratios showed significant decreases in February and March 2020, which coincided with the lockdown period in China. "The relationship between the variation ratio and the FFCO2 emissions from China should be evaluated by using an atmospheric transport model and a set of CO2s and CH4 flux maps," the study authors noted. /IANS