August 15th, 2024
A comprehensive understanding of methane’s contribution as a greenhouse gas in the atmosphere, crucial for effective climate mitigation policies, remains elusive due to the overlap of natural (wetlands) and anthropogenic (natural gas, agriculture, sewage, landfills) sources. Larry Horowitz and Vaishali Naik, both Physical Scientists at GFDL, are co-Principal Investigators on a study that was awarded a 3-year grant from NOAA’s Climate Program Office, which will add methane stable isotopologue chemistry to an atmospheric component of a global Earth system model. The team’s goal is to improve the representation of sources and sinks of atmospheric methane in the GFDL AM4.1 model, which would then allow realistic assessment of the methane mitigation policies.
Dr. Naik explained that “representation of isotopologue fractionation of methane in Earth system models constrained by observations will help improve our understanding of the contribution of the natural and anthropogenic sources to atmospheric methane levels.”
To date, the isotopologues of methane have proven to be useful tools for providing information about local-to-global source attribution changes, but these have primarily been applied via local or extremely simple global models. Dr. Horowitz noted that “this study will constrain the local-to-global methane budget by simulating stable methane isotopologues within GFDL’s AM4.1 model and comparing results to new regional and existing global observations.” This study will be carried out with lead Principal Investigator Lee T. Murray and co-Principal Investigator Vasilii V. Petrenko, from University of Rochester in New York.
This is one of eight new projects just announced by NOAA’s Climate Program Office, which aim to increase our understanding of methane’s significance in the atmosphere by exploring global, regional and local concentration and trends, modeling methane budgets and frameworks for measurement and verification of emissions. The competitively selected projects total $5.3 million in grants. These projects will improve understanding of atmospheric methane sources and sinks in order to inform successful policies for reducing greenhouse gas emissions, address major sources of uncertainty in methane measurements and modeling, and ultimately reduce community-level methane emissions.
Atmospheric methane is a potent greenhouse gas that has been steadily increasing since the beginning of the Industrial Era, much like CO2, with a brief leveling off from 1999 to 2006, before resuming its increase from 2007 on. In 2021, global average methane concentrations increased by the highest amount since measurements began in 1983.
The main sources of methane are both natural (wetlands, lakes, wild animals, termites and geological seeps) and human-caused (agriculture, waste management, fossil fuel exploitation and biomass burning). There are limited capabilities of quantifying, verifying, and monitoring the sources and sinks, which can make it difficult to understand and mitigate methane emissions. An understanding of where methane comes from and how it’s removed from the atmosphere is critical for adopting successful policies for reducing greenhouse gas emissions.