| 1. |
- Andrews, Timothy, et al.
(författare)
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On the Effect of Historical SST Patterns on Radiative Feedback
- 2022
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 127:18
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the dependence of radiative feedback on the pattern of sea-surface temperature (SST) change in 14 Atmospheric General Circulation Models (AGCMs) forced with observed variations in SST and sea-ice over the historical record from 1871 to near-present. We find that over 1871–1980, the Earth warmed with feedbacks largely consistent and strongly correlated with long-term climate sensitivity feedbacks (diagnosed from corresponding atmosphere-ocean GCM abrupt-4xCO2 simulations). Post 1980, however, the Earth warmed with unusual trends in tropical Pacific SSTs (enhanced warming in the west, cooling in the east) and cooling in the Southern Ocean that drove climate feedback to be uncorrelated with—and indicating much lower climate sensitivity than—that expected for long-term CO2 increase. We show that these conclusions are not strongly dependent on the Atmospheric Model Intercomparison Project (AMIP) II SST data set used to force the AGCMs, though the magnitude of feedback post 1980 is generally smaller in nine AGCMs forced with alternative HadISST1 SST boundary conditions. We quantify a “pattern effect” (defined as the difference between historical and long-term CO2 feedback) equal to 0.48 ± 0.47 [5%–95%] W m−2 K−1 for the time-period 1871–2010 when the AGCMs are forced with HadISST1 SSTs, or 0.70 ± 0.47 [5%–95%] W m−2 K−1 when forced with AMIP II SSTs. Assessed changes in the Earth's historical energy budget agree with the AGCM feedback estimates. Furthermore satellite observations of changes in top-of-atmosphere radiative fluxes since 1985 suggest that the pattern effect was particularly strong over recent decades but may be waning post 2014.
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| 2. |
- Loeb, Norman G., et al.
(författare)
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New Generation of Climate Models Track Recent Unprecedented Changes in Earth's Radiation Budget Observed by CERES
- 2020
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 47:5
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Tidskriftsartikel (refereegranskat)abstract
- We compare top-of-atmosphere (TOA) radiative fluxes observed by the Clouds and the Earth's Radiant Energy System (CERES) and simulated by seven general circulation models forced with observed sea-surface temperature (SST) and sea-ice boundary conditions. In response to increased SSTs along the equator and over the eastern Pacific (EP) following the so-called global warming hiatus of the early 21st century, simulated TOA flux changes are remarkably similar to CERES. Both show outgoing shortwave and longwave TOA flux changes that largely cancel over the west and central tropical Pacific, and large reductions in shortwave flux for EP low-cloud regions. A model's ability to represent changes in the relationship between global mean net TOA flux and surface temperature depends upon how well it represents shortwave flux changes in low-cloud regions, with most showing too little sensitivity to EP SST changes, suggesting a pattern effect that may be too weak compared to observations.
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| 3. |
- Stephens, Graeme L., et al.
(författare)
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The changing nature of Earth's reflected sunlight
- 2022
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Ingår i: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences. - : The Royal Society. - 1364-5021 .- 1471-2946. ; 478:2263
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Tidskriftsartikel (refereegranskat)abstract
- The increased rate of sea-level rise suggests that Earth's energy imbalance is also increasing over time. This study assesses whether 20 years of direct observations of this energy imbalance from Earth-orbiting satellites support the existence of a real trend in this imbalance and the components of it and finds. Changes to the imbalance observed are found to be consistent across multiple sources of observations. The majority of recent studies now clearly point to this energy imbalance being positive, while forced by increasing greenhouse gas concentrations in the atmosphere, being amplified significantly by decreases to the amount of sunlight reflected by Earth to space. Here, we show that the global changes observed appear largely from reductions in the amount of sunlight scattered by Earth's atmosphere. These reductions, in turn, are found to be almost equally split between reduced reflection from the cloudy and clear regions of the atmosphere, with the latter being suggestive of reduced scattering by aerosol particles over the observational period. Climate models, however, show an almost exclusive response from clouds, and a slightly exaggerated darkening of the surface. Thus, models that match the global shortwave change do so for the wrong reasons.
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