Importance of Uncertainties in the Spatial Distribution of Preindustrial Wildfires for Estimating Aerosol Radiative Forcing. Issue 6 (22nd March 2021)

• Record Type: Journal Article
• Authors: Wan, J. S.; Hamilton, D. S.; Mahowald, N. M.
• Is Part Of: Geophysical research letters. Volume 48:Issue 6(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-03-22
• Subjects: aerosol radiative forcing -- fires -- preindustrial aerosol -- regional aerosol impacts; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL089758
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Uncertainty in preindustrial aerosol emissions, including fires, is one of the largest sources of uncertainty in estimating anthropogenic radiative forcing. Here, we quantify the range in aerosol forcing associated with uncertainty in the location and magnitude of preindustrial fire emissions in a climate model based on four emission estimates. With varied emission location and magnitude among the fire estimates, we find the change in aerosol forcing from present‐day to preindustrial is between −0.4 and 0.3 W/m 2 for direct radiative forcing and between −1.8 and 0.6 W/m 2 for cloud albedo forcing. Altering only the spatial distribution of preindustrial fires for a fixed magnitude adds a previously unaccounted 25% uncertainty to the total aerosol radiative forcing range. Future studies must account for the uncertainty in the spatial distribution of fire and other aerosol emissions as regional differences contribute substantial additional uncertainty to anthropogenic radiative forcing estimates and the resultant climate sensitivity. Plain Language Summary: Fires are a key driver of changes to physical landscapes, biogeochemical cycles, and climate on a variety of spatial and temporal scales. In particular, the aerosol particles emitted in fire smoke influence regional and global climate by altering the atmospheric energy budget via interactions with solar radiation and by modifying clouds. In this study, we quantify the aerosol radiative impacts on climate from changing the location and strength of preindustrial fires for four different emission representations. We find that changing only the location of preindustrial fires contributes an additional 25% uncertainty to the estimated range of radiative impacts calculated. Thus, it is important to consider not only changes in the magnitude of fires, but in which regions past fires are occurring when estimating human‐induced changes to climate and the Earth System. Key Points: This study explores the radiative impacts of changing the spatial distribution and total magnitude of preindustrial fire emissions For a fixed emission magnitude, spatial uncertainty in fires adds 25% to the total radiative forcing range Global aerosol radiative forcing scales linearly with black carbon burden