A global enhancement of hydrogen cyanide in the lower stratosphere throughout 2016

Sheese, Patrick E.; Walker, Kaley A.; Boone, C. D.

doi:10.1002/2017gl073519

Cited by 11 publications

(16 citation statements)

References 43 publications

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“…According to the results of Pumphrey et al (2018), data from LAU in the southern mid-latitudes are outside the region of the strongest HCN signal. This is also evident in the zonal mean HCN climatologies of Sheese et al (2017). However, ENSO accounts for up to 51 % of the variability in our biomass burning proxy record.…”

Section: Contrasting Correlation Patterns For [Ch 4 ] and δ 13 Ch 4 Vmentioning

confidence: 52%

Limited impact of El Niño–Southern Oscillation on variability and growth rate of atmospheric methane

et al. 2018

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Abstract. The El Niño–Southern Oscillation (ENSO) has been suggested as a strong forcing in the methane cycle and as a driver of recent trends in global atmospheric methane mole fractions [CH4]. Such a sensitivity of the global CH4 budget to climate events would have important repercussions for climate change mitigation strategies and the accuracy of projections for future greenhouse forcing. Here, we test the impact of ENSO on atmospheric CH4 in a correlation analysis. We use local and global records of [CH4], as well as stable carbon isotopic records of atmospheric CH4 (δ13CH4), which are particularly sensitive to the combined ENSO effects on CH4 production from wetlands and biomass burning. We use a variety of nominal, smoothed, and detrended time series including growth rate records. We find that at most 36 % of the variability in [CH4] and δ13CH4 is attributable to ENSO, but only for detrended records in the southern tropics. Trend-bearing records from the southern tropics, as well as all studied hemispheric and global records, show a minor impact of ENSO, i.e. < 24 % of variability explained. Additional analyses using hydrogen cyanide (HCN) records show a detectable ENSO influence on biomass burning (up to 51 %–55 %), suggesting that it is wetland CH4 production that responds less to ENSO than previously suggested. Dynamics of the removal by hydroxyl likely counteract the variation in emissions, but the expected isotope signal is not evident. It is possible that other processes obscure the ENSO signal, which itself indicates a minor influence of the latter on global CH4 emissions. Trends like the recent rise in atmospheric [CH4] can therefore not be attributed to ENSO. This leaves anthropogenic methane sources as the likely driver, which must be mitigated to reduce anthropogenic climate change.

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Section: Contrasting Correlation Patterns For [Ch 4 ] and δ 13 Ch 4 Vmentioning

confidence: 52%

Limited impact of El Niño–Southern Oscillation on variability and growth rate of atmospheric methane

et al. 2018

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“…According to the results of Pumphrey et al (2018), data from LAU in the Southern mid-latitudes are outside the region of the strongest HCN signal. This is also evident in the zonal mean HCN climatologies of (Sheese et al, 2017). Yet, ENSO accounts for up to 51% of the variability in our biomass burning proxy record.…”

Section: Contrasting Correlation Patterns For [Ch4] and  13 Ch4 Versmentioning

confidence: 58%

Limited impact of El Niño – Southern Oscillation on the methane cycle

Schaefer¹,

Smale²,

Nichol³

et al. 2018

Preprint

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Abstract. The El Ni&#241;o &#8211; Southern Oscillation (ENSO) has been suggested as a strong forcing in the methane cycle and as a driver of recent trends in global atmospheric methane levels. Such a sensitivity of the global CH4 budget to climate events would have important repercussions for climate change mitigation strategies and the accuracy of projections for future greenhouse forcing. Here, we test the impact of ENSO on the CH4 cycle in a correlation analysis. We use local and global records of methane mixing ratio [CH4], as well as stable carbon isotopic records of atmospheric CH4 (&#948;13CH4), which are particularly sensitive to the combined ENSO effects on CH4 production from wetlands and biomass burning. We use a variety of nominal, smoothed and detrended time series including growth rate records. We find that at most 38&#8201;% of the variability in [CH4] and &#948;13CH4 is attributable to ENSO, but only for detrended records in the Southern tropics. Trend-bearing records from the Southern tropics, as well as all studied hemispheric and global records show a minor impact of ENSO, i.e. <&#8201;25&#8201;% of variability explained. Additional analyses using hydrogen cyanide (HCN) records show a detectable ENSO influence on biomass burning (up to 51&#8201;%&#8211;55&#8201;%), suggesting that it is wetland CH4 production that responds less to ENSO than previously suggested. It is possible that other processes obscure the ENSO signal, which itself indicates a minor influence of the latter on CH4 emissions. Trends like the recent rise in atmospheric [CH4] can therefore not be attributed to ENSO. This leaves anthropogenic methane sources as the likely driver, which must be mitigated to reduce anthropogenic climate change.

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“…Uncertainties of ACE‐FTS CO version 2.2 are better than 15% in the upper troposphere (8–12 km) and better than 30% in the lower stratosphere (12–30 km, Clerbaux et al., 2008). We use ACE‐FTS v4.1 measurements of CO and HCN (Boone et al., 2020; Sheese et al., 2017) from February 2004 to December 2019. Monthly mean data are constructed by combining all the available measurements within the latitude bands (see Park et al., 2013).…”

Section: Satellite Data and Model Descriptionmentioning

confidence: 99%