Effect of the temperature dependence of gas absorption in climate feedback

Huang, Yi; Ramaswamy, V.

doi:10.1029/2006jd007398

Cited by 5 publications

(4 citation statements)

References 15 publications

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“…Continuum absorption, on the other hand, decreases with temperature if gas partial pressures are held fixed with warming. The spectral features of our temperature‐dependent opacity deviation term compare closely to the “absorptivity effect” first discussed by Huang and Ramaswamy (2007) (see their Figure 4), though we find a smaller magnitude of Δ T (likely in part because Huang and Ramaswamy (2007) also include stratospheric warming). The nonlinear averaging deviation, Δ N ( ν ) (Figure 2a, purple), varies in sign across the spectrum, tracking the difference between the monochromatic brightness temperature

\left({T}_{b}^{\nu }\right)

and the effective emission temperature T e .…”

Section: Resultssupporting

confidence: 83%

“…In addition to the dominant CRONIN AND DUTTA 10.1029/2023MS003729 3 of 19 term of stratospheric masking, we find two other deviation terms that each have magnitude ∼0.1 W m −2 K −1 , but tend to cancel one another. One term, which we call "temperature-dependent opacity," is due to the general dependence of gas absorption coefficients on temperature, even at fixed concentrations, and was first discussed by Huang and Ramaswamy (2007). The other term relates to the nonlinear averaging of flux derivatives over emitting temperatures (in height) and wavenumbers (ν).…”

Section: Cronin and Duttamentioning

confidence: 99%

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How Well do We Understand the Planck Feedback?

Cronin¹

2023

J Adv Model Earth Syst

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A reference or “no‐feedback” radiative response to warming is fundamental to understanding how much global warming will occur for a given change in greenhouse gases or solar radiation incident on the Earth. The simplest estimate of this radiative response is given by the Stefan‐Boltzmann law as −4σTe‾3≈−3.8 ${-}4\sigma {\overline{{T}_{e}}}^{3}\approx -3.8$ W m−2 K−1 for Earth's present climate, where trueTe‾ $\overline{{T}_{e}}$ is a global effective emission temperature. The comparable radiative response in climate models, widely called the “Planck feedback,” averages −3.3 W m−2 K−1. This difference of 0.5 W m−2 K−1 is large compared to the uncertainty in the net climate feedback, yet it has not been studied carefully. We use radiative transfer models to analyze these two radiative feedbacks to warming, and find that the difference arises primarily from the lack of stratospheric warming assumed in calculations of the Planck feedback (traditionally justified by differing constraints on and time scales of stratospheric adjustment relative to surface and tropospheric warming). The Planck feedback is thus masked for wavelengths with non‐negligible stratospheric opacity, and this effect implicitly acts to amplify warming in current feedback analysis of climate change. Other differences between Planck and Stefan‐Boltzmann feedbacks arise from temperature‐dependent gas opacities, and several artifacts of nonlinear averaging across wavelengths, heights, and different locations; these effects partly cancel but as a whole slightly destabilize the Planck feedback. Our results point to an important role played by stratospheric opacity in Earth's climate sensitivity, and clarify a long‐overlooked but notable gap in our understanding of Earth's reference radiative response to warming.

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\left({T}_{b}^{\nu }\right)

and the effective emission temperature T e .…”

Section: Resultssupporting

confidence: 83%

Section: Cronin and Duttamentioning

confidence: 99%

How Well do We Understand the Planck Feedback?

Cronin¹

2023

J Adv Model Earth Syst

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“…The importance of the continuum for longwave radiative transfer calculations has been demonstrated in numerous studies [e.g., Clough et al , 1992; Ellingson et al , 1991; Huang and Ramaswamy , 2007; Huang et al , 2007; Schwarzkopf and Ramaswamy , 1999]. Details of the longwave radiative effects of the continuum are summarized in section 3.1 below.…”

Section: Introductionmentioning

confidence: 99%

An assessment of recent water vapor continuum measurements upon longwave and shortwave radiative transfer

Paynter

Ramaswamy

2011

J. Geophys. Res.

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[1] Recent measurements of the water vapor continuum have been combined to form an empirical continuum termed the BPS continuum model. This covers the 800 to 7500 cm −1 spectral region for the self continuum and most of the major absorbing spectral regions between 240 and 7300 cm −1 for the foreign continuum. Longwave (i.e., absorption/emission of terrestrial radiation between 1 and 3000 cm −1 ) and shortwave (i.e., using solar radiation as a source and considering atmospheric absorption between 1000 and 17000 cm −1 ) line by line (LBL) radiative transfer calculations have been performed for clear-sky conditions in three standard test atmospheres using line data from the HITRAN database. This has allowed BPS to be compared to the commonly used CKD and MT CKD continuum models, in addition to conducting a more detailed investigation of the separate roles of the self and foreign continua than previously provided in the literature. Using uncertainties obtained from multiple experimental studies it has been possible to estimate the upper and lower limits of the effects due to the continuum in many spectral regions. The outgoing longwave radiation in a midlatitude-summer (MLS) atmosphere calculated by all three continuum models agree to within 0.6 Wm −2 with a ±1.1 Wm −2 estimated uncertainty. The corresponding values for surface downwelling radiation are 1.3 Wm −2 ± 2.5 Wm −2 . For shortwave absorption, the different models agree within 1.0%, with an estimated uncertainty of ±1.7%. However, the three models differ in the amount by which the self and foreign continua contribute to shortwave absorption.Citation: Paynter, D. J., and V. Ramaswamy (2011), An assessment of recent water vapor continuum measurements upon longwave and shortwave radiative transfer,

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“…If the sum of these effects is a cooling effect, it is essential to assess what is the change in the radiative flux at TOA. Huang and Ramaswamy [14] have calculated the absorptivity effect and the Planck effect (emission rate) in the troposphere. The absorption in the gas phase increases in lower temperatures but at the same time emissivity decreases and the result is largely one of cancellation.…”

Section: Stratospheric Cooling and Warming Effectsmentioning

confidence: 99%

Radiative Forcing and Climate Sensitivity of Carbon Dioxide (CO2) Fine-tuned with CERES Data

Ollila

2023

CJAST

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An updated effective radiative forcing (ERF) value for constructing a simplified logarithmic forcing equation, and a transient climate response (TCR) value, are presented for CO2, CH4, and N2O. The results are based on line-by-line (LBL) calculations utilizing the HITRAN database and the CERES radiation flux data for fine-tuning. The ERF value derived when doubling the CO2 concentration from 280 ppm (2xCO2) is 2.65 Wm-2 which is in line with the instantaneous radiative forcing (IRF) values of climate models referred to by the IPCC. The difference between the ERF values comes from the stratospheric cooling effect. It is a question about an essential paradigm change of the IPCC approach. In the former 2xCO2 value of 3.7 Wm-2, its portion was about 5 %, and in the present value, it is about 30 %. According to this study, the same effect is 10 %. The updated TCR value is 0.7 ±0.15 °C.

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Effect of the temperature dependence of gas absorption in climate feedback

Cited by 5 publications

References 15 publications

How Well do We Understand the Planck Feedback?

How Well do We Understand the Planck Feedback?

An assessment of recent water vapor continuum measurements upon longwave and shortwave radiative transfer

Radiative Forcing and Climate Sensitivity of Carbon Dioxide (CO2) Fine-tuned with CERES Data

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