Defratyka et al. report ethane measurements from a spectroscopic instrument originally not designed to make an ethane measurement. Ethane has a small interfering absorption peak for an instrument that reports isotopic measurements of CO2 and CH4. Defratyka et al. quantify this peak, and although the ethane measurement has low precision, use it to quantify the ethane to CH4 ratio from natural gas emissions. Although the ethane measurement is not very good, and the application of this measurement

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... is limited, it nonetheless could be of some use to the scientific community. However, before this paper is ready for publication, I think some issues must be addressed. C1