English: Graph shows the hemispheric and global mean concentrations of carbon tetrachloride (tetrachloromethane, CCl₄, R-10) in earth's atmosphere versus time. X-axis data interval is monthly. Y-axis concentration is parts per trillion.

The data represent a mean of combined data from the HATS (Halocarbon and Atmospheric Trace Species) programs; which include up to 15 sampling sites that are distributed over the northern and southern hemispheres. Most emissions originate at northern latitudes, and are mixed through the troposphere of both hemispheres after about 1-2 years.

Data sampling and analysis by:
Halocarbons and Other Atmospheric Trace Species Group / Global Monitoring Division / Earth Systems Research Laboratories / United States National Oceanic and Atmospheric Administration

https://www.esrl.noaa.gov/gmd/hats/