Biomass burning drives changes in greenhouse gases, climate-forcing aerosols, and global atmospheric chemistry. There is controversy about the magnitude and timing of changes in biomass burning emissions on millennial time scales from preindustrial to present and about the relative importance of climate change and human activities as the underlying cause. Biomass burning is one of two notable sources of ethane in the preindustrial atmosphere. Here, we present ice core ethane measurements from Antarctica and Greenland that contain information about changes in biomass burning emissions since 1000 CE (Common Era). The biomass burning emissions of ethane during the Medieval Period (1000–1500 CE) were higher than present day and declined sharply to a minimum during the cooler Little Ice Age (1600–1800 CE). Assuming that preindustrial atmospheric reactivity and transport were the same as in the modern atmosphere, we estimate that biomass burning emissions decreased by 30 to 45% from the Medieval Period to the Little Ice Age. The timing and magnitude of this decline in biomass burning emissions is consistent with that inferred from ice core methane stable carbon isotope ratios but inconsistent with histories based on sedimentary charcoal and ice core carbon monoxide measurements. This study demonstrates that biomass burning emissions have exceeded modern levels in the past and may be highly sensitive to changes in climate.
Estimating fire emissions prior to the satellite era is challenging because observations are limited, leading to large uncertainties in the calculated aerosol climate forcing following the preindustrial era. This challenge further limits the ability of climate models to accurately project future climate change. Here, we reconstruct a gridded dataset of global biomass burning emissions from 1750 to 2010 using inverse analysis that leveraged a global array of 31 ice core records of black carbon deposition fluxes, two different historical emission inventories as a priori estimates, and emission-deposition sensitivities simulated by the atmospheric chemical transport model GEOS-Chem. The reconstructed emissions exhibit greater temporal variabilities which are more consistent with paleoclimate proxies. Our ice core constrained emissions reduced the uncertainties in simulated cloud condensation nuclei and aerosol radiative forcing associated with the discrepancy in preindustrial biomass burning emissions. The derived emissions can also be used in studies of ocean and terrestrial biogeochemistry.
more » « less- PAR ID:
- 10503588
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Biomass burning is an important component of the Earth system in terms of global biogeochemistry, atmospheric composition, climate, terrestrial ecology, and land use. This study examines published ice core trace gas measurements of acetylene, ethane, and methane, which have been used as proxies for paleofire emissions. We investigate the consistency of these records for the past 1,000 years in terms of (1) temporal trends in global fire emissions and (2) quantitative estimates for changes in global burning (dry matter burned per year). Three‐dimensional transport and box models were used to construct emissions scenarios for the trace gases consistent with each ice core record. Burning histories were inferred from trace gas emissions by accounting for biome‐specific emission factors for each trace gas. The temporal trends in fire inferred from the trace gases are in reasonable agreement, with a large decline in biomass burning emissions from the Medieval Period (MP: 1000–1500 CE) to the Little Ice Age (LIA: 1650–1750 CE). However, the three trace gas ice core records do not yield a consistent fire history, even assuming dramatic (and unrealistic) changes in the spatial distribution of fire and biomes. Substantial changes in other factors such as meteorological transport or atmospheric photochemical lifetimes appear to be required to reconcile the trace gas records.
