Wildland fire emissions, carbon, and climate: U.S. emissions inventories

• We examine how emissions inventories for wildland fire are developed.
• Comparisons are made between four emissions inventories for the contiguous USA.
• Seasonal, interannual, and regional differences are examined.
• The effects of modeling choices on emissions inventories are detailed.
• Current knowledge gaps and potential for future improvements and discussed.

Emissions from wildland fire are both highly variable and highly uncertain over a wide range of temporal and spatial scales. Wildland fire emissions change considerably due to fluctuations from year to year with overall fire season severity, from season to season as different regions pass in and out of wildfire and prescribed fire periods, and from day to day as weather patterns affect large wildfire growth events and prescribed fire windows. Emissions from wildland fire are highly uncertain in that every component used to calculate wildland fire emissions is uncertain – including how much fire occurs and at what time during the year, assessments of available fuel stocks, consumption efficiency, and emissions factors used to calculate the final emissions. As shown here, these component uncertainties result in large-scale differences between estimation methods of wildland fire emissions including greenhouse gas totals, particulate matter totals, and other emissions. Four recent emissions inventories for the contiguous United States are compared to determine inter-inventory differences and to examine how methodological choices result in different annual totals and patterns of temporal and spatial variability. Inter-model variability is detailed for several current models, and current knowledge gaps and future directions for progressing fire emissions inventories are discussed.