Spacecraft were not detecting all of the spectroscopic signatures of the gas, for example, and ground - based observers had to contend with interference from methane and other trace gases in Earth's atmosphere. (sciencemag.org)
Scenario C is a more drastic curtailment of emissions of chlorfluorocarbon (CFC) emissions by 2000 and reduction of CO2 and other trace gas emissions to a level such that the annual growth rates are zero (ie., the sources balance the sinks) by year 2000. (climateaudit.org)
The Trace Gas Orbiter can detect and analyse methane and other trace gases even in extremely low concentrations, with an improved accuracy of three orders of magnitude over previous measurements. (astrobio.net)