TY - JOUR
T1 - Forcing, Cloud Feedbacks, Cloud Masking, and Internal Variability in the Cloud Radiative Effect Satellite Record
AU - Raghuraman, Shiv Priyam
AU - Paynter, David
AU - Menzel, Raymond
AU - Ramaswamy, And V.
N1 - We thank the three anonymous reviewers for their constructive feedback. We thank Leo Donner and Yi Ming for internally reviewing this manuscript. Numerical simulations were conducted with GFDL computational resources. S.P.R. was supported by the Future Investigators in NASA Earth and Space Science and Technology Award 80NSSC19K1372 and partially supported by the High Meadows Environmental Institute at Princeton University through the Mary and Randall Hack ‘69 Research Fund. We acknowledge the World Climate Research Programme, which, through its Working Group on Coupled Modelling, coordinated and promoted CMIP6. We thank the climate modeling groups for producing and making available their model output, the Earth System Grid Federation (ESGF) for archiving the data and providing access, and the multiple funding agencies that support CMIP6 and ESGF.
Acknowledgments. We thank the three anonymous reviewers for their constructive feedback. We thank Leo Donner and Yi Ming for internally reviewing this manuscript. Numerical simulations were conducted with GFDL computational resources. S.P.R. was supported by the Future Investigators in NASA Earth and Space Science and Technology Award 80NSSC19K1372 and partially supported by the High Meadows Environmental Institute at Princeton University through the Mary and Randall Hack ‘69 Research Fund. We acknowledge the World Climate Research Programme, which, through its Working Group on Coupled Modelling, coordinated and promoted CMIP6. We thank the climate modeling groups for producing and making available their model output, the Earth System Grid Federation (ESGF) for archiving the data and providing access, and the multiple funding agencies that support CMIP6 and ESGF.
PY - 2023/6/15
Y1 - 2023/6/15
N2 - Satellite observations show a near-zero trend in the top-of-atmosphere global-mean net cloud radiative effect (CRE), suggesting that clouds did not further cool nor heat the planet over the last two decades. The causes of this observed trend are unknown and can range from effective radiative forcing (ERF) to cloud feedbacks, cloud masking, and internal variability. We find that the near-zero NetCRE trend is a result of a significant negative trend in the longwave (LW) CRE and a significant positive trend in the shortwave (SW) CRE, cooling and heating the climate system, respectively. We find that it is exceptionally unlikely (<1% probability) that internal variability can explain the observed LW and SW CRE trends. Instead, the majority of the observed LWCRE trend arises from cloud masking wherein increases in greenhouse gases reduce OLR in all-sky conditions less than in clear-sky conditions. In SWCRE, rapid cloud adjustments to greenhouse gases, aerosols, and natural forcing agents (ERF) explain a majority of the observed trend. Over the northeast Pacific, we show that ERF, hitherto an ignored factor, contributes as much as cloud feedbacks to the observed SWCRE trend. Large contributions from ERF and cloud masking to the global-mean LW and SW CRE trends are supplemented by negative LW and positive SW cloud feedback trends, which are detectable at 80%–95% confidence depending on the observational uncertainty assumed. The large global-mean LW and SW cloud feedbacks cancel, leaving a small net cloud feedback that is unconstrained in sign, implying that clouds could amplify or dampen global warming.
AB - Satellite observations show a near-zero trend in the top-of-atmosphere global-mean net cloud radiative effect (CRE), suggesting that clouds did not further cool nor heat the planet over the last two decades. The causes of this observed trend are unknown and can range from effective radiative forcing (ERF) to cloud feedbacks, cloud masking, and internal variability. We find that the near-zero NetCRE trend is a result of a significant negative trend in the longwave (LW) CRE and a significant positive trend in the shortwave (SW) CRE, cooling and heating the climate system, respectively. We find that it is exceptionally unlikely (<1% probability) that internal variability can explain the observed LW and SW CRE trends. Instead, the majority of the observed LWCRE trend arises from cloud masking wherein increases in greenhouse gases reduce OLR in all-sky conditions less than in clear-sky conditions. In SWCRE, rapid cloud adjustments to greenhouse gases, aerosols, and natural forcing agents (ERF) explain a majority of the observed trend. Over the northeast Pacific, we show that ERF, hitherto an ignored factor, contributes as much as cloud feedbacks to the observed SWCRE trend. Large contributions from ERF and cloud masking to the global-mean LW and SW CRE trends are supplemented by negative LW and positive SW cloud feedback trends, which are detectable at 80%–95% confidence depending on the observational uncertainty assumed. The large global-mean LW and SW cloud feedbacks cancel, leaving a small net cloud feedback that is unconstrained in sign, implying that clouds could amplify or dampen global warming.
KW - Climate models
KW - Cloud radiative effects
KW - Clouds
KW - Feedback
KW - Forcing
KW - Satellite observations
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U2 - 10.1175/JCLI-D-22-0555.1
DO - 10.1175/JCLI-D-22-0555.1
M3 - Article
AN - SCOPUS:85164272596
SN - 0894-8755
VL - 36
SP - 4151
EP - 4167
JO - Journal of Climate
JF - Journal of Climate
IS - 12
ER -