Significant Effective Radiative Forcing of Stratospheric Wildfire Smoke

The radiative forcing (RF) of volcanic sulfate is well quantified. However, the RF of pyrocumulonimbus (pyroCb) smoke with absorbing carbonaceous aerosols has not been considered in climate assessment reports. With the Community Earth System Model, we studied two record-breaking wildfire events, the 2017 Pacific Northwest Event (PNE) and the 2019-2020 Australian New Year event (ANY), that perturbed stratospheric chemistry and the earth's radiation budget. We calculated a global annual-mean effective RF (ERF) of -0.04 +/- 0.02 and -0.17 +/- 0.02 W/m(2) at the top of the atmosphere (TOA) for PNE and ANY, respectively. The complexity of longwave RF led to an uncertainty of about 50% in the ERF at the TOA among climate models. We found that modeled ERF from wildfire smoke was 70%-270% more negative than the ERF of mass-equivalent sulfate aerosol, highlighting its important role in the climate radiative budget.

Automated summary

This study used the Community Earth System Model to investigate the wildfire events in 2017 and 2019-2020 and found that the radiative forcing of wildfire smoke is more significant than that of equivalent sulfate aerosols, highlighting its important role in the climate radiative budget.