Methane's Solar Radiative Forcing

Abstract Methane (CH4) has significant absorption bands at wavelengths of 1.7, 2.3, 3.3 and 7.6 μm which absorb incoming solar ‘shortwave’ (SW) radiation and contribute to radiative forcing (RF). A comprehensive quantification of CH4 SW RF is presented using a narrow‐band radiative transfer model to...

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Main Authors: R. E. Byrom, K. P. Shine
Format: Article
Language:English
Published: Wiley 2022-08-01
Series:Geophysical Research Letters
Subjects:
Online Access:https://doi.org/10.1029/2022GL098270
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author R. E. Byrom
K. P. Shine
author_facet R. E. Byrom
K. P. Shine
author_sort R. E. Byrom
collection DOAJ
description Abstract Methane (CH4) has significant absorption bands at wavelengths of 1.7, 2.3, 3.3 and 7.6 μm which absorb incoming solar ‘shortwave’ (SW) radiation and contribute to radiative forcing (RF). A comprehensive quantification of CH4 SW RF is presented using a narrow‐band radiative transfer model to calculate spatially and monthly resolved estimates of CH4 SW RF and its impact on longwave (LW) stratospheric temperature adjusted RF (SARF). These new calculations include satellite measurements of CH4 distribution and spectrally varying surface albedo, and include absorption of solar mid‐infrared radiation by methane's 7.6 μm band. These factors substantially influence methane's SW effect. For a 750–1,800 ppb perturbation, the all‐sky top‐of‐atmosphere SW instantaneous RF is 0.082 W m−2; at the tropopause it is 0.002 W m−2, considerably smaller than previous estimates. Including the impact of SW absorption on stratospheric temperature increases tropopause SARF by 0.039 W m−2 (or 7%) compared to the LW‐only SARF.
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spelling doaj-art-b9840ffc149a4914bb8015e12c9e17c02025-08-20T02:12:53ZengWileyGeophysical Research Letters0094-82761944-80072022-08-014915n/an/a10.1029/2022GL098270Methane's Solar Radiative ForcingR. E. Byrom0K. P. Shine1Department of Meteorology University of Reading Reading UKDepartment of Meteorology University of Reading Reading UKAbstract Methane (CH4) has significant absorption bands at wavelengths of 1.7, 2.3, 3.3 and 7.6 μm which absorb incoming solar ‘shortwave’ (SW) radiation and contribute to radiative forcing (RF). A comprehensive quantification of CH4 SW RF is presented using a narrow‐band radiative transfer model to calculate spatially and monthly resolved estimates of CH4 SW RF and its impact on longwave (LW) stratospheric temperature adjusted RF (SARF). These new calculations include satellite measurements of CH4 distribution and spectrally varying surface albedo, and include absorption of solar mid‐infrared radiation by methane's 7.6 μm band. These factors substantially influence methane's SW effect. For a 750–1,800 ppb perturbation, the all‐sky top‐of‐atmosphere SW instantaneous RF is 0.082 W m−2; at the tropopause it is 0.002 W m−2, considerably smaller than previous estimates. Including the impact of SW absorption on stratospheric temperature increases tropopause SARF by 0.039 W m−2 (or 7%) compared to the LW‐only SARF.https://doi.org/10.1029/2022GL098270radiative forcingmethanesolar
spellingShingle R. E. Byrom
K. P. Shine
Methane's Solar Radiative Forcing
Geophysical Research Letters
radiative forcing
methane
solar
title Methane's Solar Radiative Forcing
title_full Methane's Solar Radiative Forcing
title_fullStr Methane's Solar Radiative Forcing
title_full_unstemmed Methane's Solar Radiative Forcing
title_short Methane's Solar Radiative Forcing
title_sort methane s solar radiative forcing
topic radiative forcing
methane
solar
url https://doi.org/10.1029/2022GL098270
work_keys_str_mv AT rebyrom methanessolarradiativeforcing
AT kpshine methanessolarradiativeforcing