No inter-hemispheric δ 13 CH 4 trend observed

摘要: Arising from Kai, F. M., Tyler, S. C., Randerson, J. T. & Blake, D. R. , 194–197 (2011)10.1038/nature10259 To understand the reasons for global CH4 changes since 1990s, Kai et al.1 evaluated a combined record of observed tropospheric mole fractions as well δ13C-CH4 and δD-CH4 measurements mid latitudes both hemispheres. Their data set shows strongly decreasing inter-hemispheric difference (IHD) in −0.24 ± 0.11‰ during 1989–1993 to −0.10 0.04‰ 2001–2005, which they largely attribute rice emissions last two decades. Here we show that experimental used by are probably biased because authors only one continental mountain station (Niwot Ridge, Colorado, USA) representative entire Northern Hemisphere, thereby incorrectly determining IHD δ13C-CH4. Our more comprehensive set—representing background air hemispheres—shows has changed less than 0.05‰ 1990; conclusion drawn significant reduction NH microbial sources is, thus, not constrained our data.