Nature or Humans? Scenarios for constraining why atmospheric methane continues to rise

Zhen Zhang,  University of Maryland,  yuisheng@gmail.com (Presenter)
Abhishek Chatterjee,  NASA GSFC GMAO / GESTAR USRA,  abhishek.chatterjee@nasa.gov
Benjamin Poulter,  NASA GSFC,  benjamin.poulter@nasa.gov

Atmospheric methane (CH4) concentrations have shown a puzzling resumption of growth since 2007 following a period of stabilization from 2000 to 2006. Multiple hypotheses have been proposed to explain the temporal variation in CH4 growth, attributing the rise of atmospheric CH4 either to increases in emissions from fossil fuel activities, agriculture, and natural wetlands or to a decrease in the chemical sink hydroxyl radicals (OH). Here, we use a comprehensive ensemble of CH4 source estimates and isotopic ?13C-CH4 source signature data to show that the resumption of CH4 growth is most likely due to increased anthropogenic emissions. Our emission scenarios that reproduce best the observed atmospheric CH4 concentration and isotopic composition suggest that the agriculture, landfill, and waste sectors were responsible for 53±13% of the renewed growth over the period 2007-2017, compared to 2000-2006; industrial fossil fuel sources explained an additional 34±24%, and wetland sources contributed the least at 13±9%. Reproducing the isotopic record with wetland CH4 emissions results in unrealistic temperature sensitivity and CH4 growth rate. Our findings highlight the predominant role of anthropogenic activities in driving the growth of atmospheric CH4 concentrations and makes a strong argument for the continuity of high-resolution and high-density observations from remote-sensing missions such as TROPOMI (or future missions like MERLIN) to fully observe the impact of anthropogenic activities on the CH4 growth rate.

Poster: Poster_Zhang__131_25.pdf 

Presentation Type: Poster

Session: 2.5b Results expected from future missions

Session Date: Tuesday (6/15) 12:00 PM