Ice core and firn air 14CH4 measurements from preindustrial to present suggest that anthropogenic fossil CH4 emissions are underestimated
Loading...
Date
2019-04-08
Journal Title
Journal ISSN
Volume Title
Publisher
Copernicus GmbH
Abstract
Concentrations of atmospheric methane (CH4), a potent greenhouse gas, have more than doubled since preindustrial times yet its contemporary budget is incompletely understood, with substantial discrepancies between global emission inventories and atmospheric observations (Kirschke et al., 2013; Saunois et al., 2016). Radiomethane (14CH4) can distinguish between fossil emissions from geologic reservoirs (radiocarbon free) and contemporaneous biogenic sources, although poorly constrained direct 14CH4 emissions from nuclear reactors complicate this interpretation in the modern era (Lassey et al., 2007; Zazzeri et al 2018). It has been debated how fossil emissions (172-195 Tg CH4/yr, (Saunois et al., 2016; Schwietzke et al., 2016)) are partitioned between anthropogenic sources (such as fossil fuel extraction and consumption) and natural sources (such as geologic seeps); emission inventories suggest the latter accounts for ~50-60 Tg CH4/yr (Etiope, 2015; Etiope et al., 2008). Geologic emissions were recently shown to be much smaller at the end of the Pleistocene ~11,600 years ago (Petrenko et al. 2017); However, this period is an imperfect analog for the present day due to the much larger terrestrial ice sheet cover, lowered sea level, and more extensive permafrost. We use preindustrial ice core measurements of 14CH4 to show that natural fossil CH4 emissions to the atmosphere are ~1.7 Tg CH4/yr, with a maximum of 6.1 Tg CH4/yr (95% confidence limit), an order of magnitude smaller than estimates from global inventories. This result suggests that contemporary anthropogenic fossil emissions are likely underestimated by a corresponding amount (~48-58 Tg
CH4/yr, or ~25-33% of current estimates). © Author(s) 2019. CC Attribution 4.0 license.
Description
Keywords
Drill cores, Air, Carbon 14, Greenhouse gases, Pollution, Plumes, Industrial wastes, Fossils
Citation
Hmiel, B., Petrenko, V., Dyonisius, M., Buizert, C., Smith, A., Place, P., Harth, C., Beaudette, R., Hua, Q., Yang, B., Vimont, I., Schmitt, J., Etheridge, D., Fain, X., Weiss, R., & Severinghaus, J. (2019). Ice core and firn air 14CH4 measurements from preindustrial to present suggest that anthropogenic fossil CH4 emissions are underestimated. Paper presented to the EGU General Assembly 2019, Vienna, Austria, 7-12 April 2019. In Geophysical Research Abstracts, Vol. 21, EGU2019-11868. Retrieved from: https://meetingorganizer.copernicus.org/EGU2019/EGU2019-11868.pdf