Matthew Johnson: Current and Future Lake and Reservoir Methane Emissions - Data-driven Modeling

Abstract

Methane (CH4) contributes ~30% of present-day atmospheric warming and is the second most important greenhouse gas in terms of climate forcing, and both atmospheric concentrations and emissions of CH4 are rapidly increasing. Lakes and reservoirs have been highlighted as one of the largest natural sources of CH4 to the atmosphere and are considered one of the most uncertain components of the global CH4 budget. This presentation highlights recent advancements in data-driven modeling to quantify present-day and future emissions of CH4 from these inland water bodies on a global-scale. A major contribution from these studies was producing one of the first-ever global, spatially explicit data sets of lake and reservoir CH4 fluxes and identifying reasons why past estimates have overestimated global emission estimates. Using this knowledge gained, and the data-driven model developed in these studies, future predictions of inland water CH4 emissions were made using future climate predictions as a driver. The results indicate total lake and reservoir CH4 emissions increases between 24–91% over present-day emissions (lakes: 41.6 Tg CH4 yr −1; reservoirs: 10.1 Tg CH4 yr −1) under the IPCC Shared Socioeconomic Pathway (SSP) climate change scenarios SSP1-2.6 to SSP5-8.5 by 2080–2099. These studies have addressed multiple gaps and uncertainties in previous studies and represent an important contribution to studies of the global CH4 budget.

Bio

Dr. Matthew Johnson is a Research Scientist and Branch Chief of the Biospheric Science Branch in the Earth Science Division at NASA Ames Research Center.  He received his PhD in Atmospheric Sciences from North Carolina State University in December 2012, where his dissertation focused on global modeling of mineral dust aerosol transport, chemistry, and deposition. He also holds an M.S. in Atmospheric Sciences and a B.S. in Meteorology from the same institution. His research focuses on the application of satellite remote-sensing and Earth System Models (ESMs) to study air quality, tropospheric composition, and greenhouse gases. He currently serves, and has served, as Principal Investigator on multiple NASA projects including those for the Aura Science Team, Atmospheric Composition Modeling and Analysis Program, Land Cover Land Use Program, Interdisciplinary Research in Earth Science Program, and Tropospheric Ozone Lidar Network. Furthermore, his work supports key international and NASA missions such as OCO-2/3, TEMPO, and TROPOMI. Dr. Johnson is recognized for his leadership in advancing atmospheric science, high-impact publications, and collaborative research with national and international partners.