GFDL - Geophysical Fluid Dynamics Laboratory

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Sensitivity of tropospheric oxidants to biomass burning emissions: implications for radiative forcing

Key Findings

  • Gas and aerosol emissions combine to increase CH4 lifetime non-linearly
  • Heterogeneous processes are partly responsible for the observed lower ozone production efficiency in northern high latitudes compared to tropical regions.
  • The radiative forcing from biomass burning is shown to vary non-linearly with biomass burning strength

Jingqiu Mao, Larry W. Horowitz, Vaishali Naik, Songmiao Fan, Junfeng Liu, Arlene M. Fiore. Journal: Geophysical Research Letters. DOI: 10.1002/grl.50210

Summary

Biomass burning is one of the largest sources of trace gases and aerosols in the atmosphere, and has profound influence on tropospheric oxidants and radiative forcing. Using a fully coupled chemistry-climate model (GFDL AM3), the authors found that co-emission of trace gases and aerosol from present-day biomass burning increases the global tropospheric ozone burden by 5.1%, and decreases global mean OH, a major sink for methane, by 6.3%.

There are large uncertainties in current estimates of direct radiative forcing from biomass burning aerosols. Despite this, the warming that results from methane and methane-induced changes in ozone and stratospheric water vapor (which can be considered an indirect chemical forcing) is comparable to the cooling from biomass burning aerosols, when both direct and indirect effects are taken into account.

At present-day emission levels, biomass burning produces atmospheric cooling, but increasing emissions to over 5 times present levels would result in warming.

photo courtesy of Cameron McNaughton