Methane Emissions from Fires: Trends and Anomalies

Biomass burning is an important source of aerosol emissions that greatly deteriorates air quality near the source and downwind regions. More importantly, large amounts of greenhouse gases (GHGs) such as carbon dioxide (CO2) and methane (CH4) are emitted from wildfires. A quantitative estimate of emissions from biomass burning is vital to understand the fire impacts on climate, weather, environment and public health because wildfires are projected to increase in frequency, severity, and extent in the warming climate. As one of the major climate drivers but with relatively short lifetime in the atmosphere, CH4 is an attractive mitigation target to restrict the pace of global warming. The estimation of spatially and temporally resolved CH4 emissions from the biomass burning sector provides critical information in developing measurement-informed CH4 inventories and assessing mitigation strategies and policy decision making. Early work in the implementation of the United States Greenhouse Gas Measurement, Monitoring, and Information System (US GHGMMIS) strategy involves the understanding of the GHG emissions from natural and anthropogenic sources. NOAA employed its Global Biomass Burning Emissions Product (GBBEPx) algorithm to estimate long-term temporal variation and geographic distribution of CH4 emissions using satellite observations from Aqua and Terra Moderate Resolution Imaging Spectroradiometer (MODIS) and Suomi NPP and NOAA-20 Visible Infrared Imaging Radiometer Suite (VIIRS). Globally, about 23 teragrams of CH4 are emitted from biomass burning every year, with nearly 49% of it released from Africa alone. We will present inter-annual variability of CH4 emissions and describe the magnitude of emissions from notable big fires such as the 2020 gigafire in California and 2023 Canadian fires and discuss the implications of treating emissions as net zero.