CH₄ is the second most important anthropogenically emitted greenhouse gas after CO₂. Its mole fraction has increased from around 722 ppb in pre-industrial times to 1824 ppb in 2013 and the anthropogenic fraction is estimated to be 60 % of the total emissions. A promising approach to improve the understanding of the CH₄ budget is the use of isotopologues to distinguish between various CH₄ source processes.

Our group uses state-of-the-art QCLAS to continuously monitor ¹²CH₄, ¹³CH₄ and CH₃D, and the respective isotope ratios δ¹³C-CH₄ and δD-CH₄. Within an ongoing project, we have realized a field-deployable, autonomous platform by coupling a compact QCLAS spectrometer to a preconcentration unit, called TRace gas EXtractor (TREX). This unit enhances CH₄ mole fractions by a factor of up to 500 above ambient levels and quantitatively separates interfering trace gases such as N₂O and CO₂ (Eyer et al. 2014, Eyer et al., 2016).