Significant Effective Radiative Forcing of Stratospheric Wildfire Smoke. Issue 17 (10th September 2022)

• Record Type: Journal Article
• Authors: Liu, Cheng‐Cheng; Portmann, Robert W.; Liu, Shang; Rosenlof, Karen H.; Peng, Yifeng; Yu, Pengfei
• Is Part Of: Geophysical research letters. Volume 49:Issue 17(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-10
• Subjects: pyroCb -- effective radiative forcing -- stratosphere -- fast adjustments; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL100175
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: 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. Plain Language Summary: Extreme wildfires can directly inject a large amount of smoke into the stratosphere. Two recent record‐breaking wildfire events influenced stratospheric chemistry and the global climate. However, the climate effects of these wildfires remain relatively unclear comparing to those of well‐known volcanic eruptions. We used a climate model to simulate the global effective radiative effects. Results show that the wildfire smokes significantly cooled the Earth system, with −0.04 ± 0.02 and −0.17 ± 0.02 W/m 2 for each fire. Longwave radiation from the stratosphere warmed by the wildfire smoke was comparable to shortwave radiative forcing. We further compared the climate effects of smoke to volcanic sulfate with the same aerosol mass injected. We found that wildfire smoke can cool the atmosphere 70%–270% more effectively than sulfate aerosol. Key Points: Longwave adjustments from the stratosphere warmed by wildfire smoke are comparable to shortwave radiative forcing The simulated annual mean effective RF (ERF) from the Australian wildfire is −0.17, −0.22, and −0.37 W/m 2 at the top of the atmosphere, 200 hPa, and the surface The simulated ERF of stratospheric wildfire smoke is 70%–270% more negative than the mass‐equivalent sulfate in the CESM‐MAM3 model