The below figures show cumulative probability distributions of carbon dioxide (CO2) and methane (CH4), the two leading greenhouse gases, as measured in March of 2019 (red) and 2020 (green) at the Harvard-China Project’s joint observatory with Tsinghua University at Miyun, north of Beijing. Depending on prevailing winds, the site sometimes measures clean background air from the northwest and sometimes polluted air from Beijing and surrounding areas. The lowest parts of the distributions represent background air, which have higher values in 2020 compared to 2019 due to annual increases in global CO2 and CH4 levels. The upper ends of the distributions represent polluted urban plumes from Beijing. Despite the increase in the global background, the latter levels are not as high in 2020 as they were in 2019, very likely due to reduced emissions from pandemic restrictions of economic activities and transportation. The comparisons of 2019 and 2020 are not yet controlled for meteorological differences in March of the two years, but the results are indicative. Units: ppm = parts per million; ppb = parts per billion.