Albedo Feedback, the Meridional Structure of the Effective Heat Diffusivity, and Climatic Sensitivity: Results from Dynamic and Diffusive Models

Held, Isaac M.; Linder, David I.; Suárez, Max J.

doi:10.1175/1520-0469(1981)038<1911:aftmso>2.0.co;2

Cited by 19 publications

(6 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Origin of the nonlinearity How does the nonlinear cooling come about in the first place? Several sources of nonlinearity previously identified in climate system (asides from ocean dynamics) can give a cooling effect, to name a few: the nonlinear cooling effect of vertical masking of both clear-sky quantities (such as water vapor) and cloud 22 , the remnant effect of the stabilized small ice-cap instability giving rise to a greater cooling than a warming under opposite forcing perturbations 40 , the negative nonlinear cloud radiative effect at surface attached to the seasonality in the polar climate 41 , plus the nonlinear atmospheric dynamics 39,42 . An parallel investigation has been undertaken through a suite of methodically designed experiments wherein sea ice formation is disabled to form an ice-free climate (see Methods and ref.…”

Section: The Linear and Nonlinear Responsementioning

confidence: 99%

Neutral modes of surface temperature and the optimal ocean thermal forcing for global cooling

Liu

Leung

et al. 2020

npj Clim Atmos Sci

View full text Add to dashboard Cite

Inquiry into the climate response to external forcing perturbations has been the central interest of climate dynamics. But the understanding of two important aspects of climate change response-nonlinearity and regionality-is still lacking. Here a Green's function approach is developed to estimate the linear response functions (LRFs) for both the linear and quadratic nonlinear response to ocean thermal forcing in a climate model, whereby the most excitable temperature modes, aka the neutral modes, can be identified for the current Earth climate. The resultant leading mode of the nonlinear response is characterized by a polaramplified global cooling pattern, unveiling an intrinsic inclination of the modern climate towards cooling. Moreover, optimal forcing patterns are identified to most efficiently excite the corresponding neutral mode patterns. The forcing-response framework developed herein can be utilized to determine the optimal forcing patterns to inform solar geoengineering experiments and to interpret regional climate response and feedback in general.npj Climate and Atmospheric Science (2020) 3:9 ; https://doi.

show abstract

Section: The Linear and Nonlinear Responsementioning

confidence: 99%

Neutral modes of surface temperature and the optimal ocean thermal forcing for global cooling

Liu

Leung

et al. 2020

npj Clim Atmos Sci

View full text Add to dashboard Cite

show abstract

“…The smooth hyperbolic tangent formulation is chosen to handle the phase transition from water to ice at 273 K in order to avoid the small ice-cap instabilities seen in models with a discontinuity in the albedo function at 273 K (Held et al 1981).…”

Section: Model Setupmentioning

confidence: 99%

Habitable Climates: The Influence of Eccentricity

Dressing

Spiegel

Scharf

et al. 2010

ApJ

138

131

View full text Add to dashboard Cite

In the outer regions of the habitable zone, the risk of transitioning into a globally frozen "snowball" state poses a threat to the habitability of planets with the capacity to host water-based life. Here, we use a one-dimensional energy balance climate model (EBM) to examine how obliquity, spin rate, orbital eccentricity, and the fraction of the surface covered by ocean might influence the onset of such a snowball state. For an exoplanet, these parameters may be strikingly different from the values observed for Earth. Since, for constant semimajor axis, the annual mean stellar irradiation scales with (1 − e 2 ) −1/2 , one might expect the greatest habitable semimajor axis (for fixed atmospheric composition) to scale as (1 − e 2 ) −1/4 . We find that this standard simple ansatz provides a reasonable lower bound on the outer boundary of the habitable zone, but the influence of both obliquity and ocean fraction can be profound in the context of planets on eccentric orbits. For planets with eccentricity 0.5, for instance, our EBM suggests that the greatest habitable semimajor axis can vary by more than 0.8 AU (78%!) depending on obliquity, with higher obliquity worlds generally more stable against snowball transitions. One might also expect that the long winter at an eccentric planet's apoastron would render it more susceptible to global freezing. Our models suggest that this is not a significant risk for Earth-like planets around Sun-like stars, as considered here, since such planets are buffered by the thermal inertia provided by oceans covering at least 10% of their surface. Since planets on eccentric orbits spend much of their year particularly far from the star, such worlds might turn out to be especially good targets for direct observations with missions such as TPF-Darwin. Nevertheless, the extreme temperature variations achieved on highly eccentric exo-Earths raise questions about the adaptability of life to marginally or transiently habitable conditions.

show abstract

“…In each of our three atmospheric models, the albedo function, A[T ], is chosen to capture a rapid ice-water transition, with values of A ∼ 0.7-0.77 well below 263 K (ice-covered surface), and values ∼ 0.25-0.3 well above 273 K (ice-free surface). To avoid albedo discontinuities, which are known to result in spurious "small ice-cap" instabilities in EBMs (e.g., Held et al (1981)), the albedo transition is performed smoothly over the range 263-273 K with a hyperbolic tangent formulation. This type of albedo prescription is standard in the context of EBMs (e.g.…”

Section: Global Radiative Balancementioning

confidence: 99%

“…Climate stability is a subtle issue, even in the context of a 1D diffusion model. Held et al (1981) describe how it is ultimately an interplay between latitudinal heat transport and albedo feedback effects that determines climate stability. Here, we will not attempt a thorough exploration of climate stability with our EBM but instead will illustrate how this issue could be critical in determining the habitability of a seasonally-forced Earth-like planet.…”

Section: Climate Stabilitymentioning

confidence: 99%

Habitable Climates

Spiegel

Menou

Scharf

2008

ApJ

110

147

View full text Add to dashboard Cite

According to the standard liquid-water definition, the Earth is only partially habitable. We reconsider planetary habitability in the framework of energy-balance models, the simplest seasonal models in physical climatology, to assess the spatial and temporal habitability of Earth-like planets. We quantify the degree of climatic habitability of our models with several metrics of fractional habitability. Previous evaluations of habitable zones may have omitted important climatic conditions by focusing on close Solar System analogies. For example, we find that model pseudo-Earths with different rotation rates or different land-ocean fractions have fractional habitabilities that differ significantly from that of the Earth itself. Furthermore, the stability of a planet's climate against albedo-feedback snowball events strongly impacts its habitability. Therefore, issues of climate dynamics may be central in assessing the habitability of discovered terrestrial exoplanets, especially if astronomical forcing conditions are different from the moderate Solar System cases.Comment: Accepted by ApJ. Several references added. 41 pages, 11 figures, 2 table

show abstract

Albedo Feedback, the Meridional Structure of the Effective Heat Diffusivity, and Climatic Sensitivity: Results from Dynamic and Diffusive Models

Cited by 19 publications

References 0 publications

Neutral modes of surface temperature and the optimal ocean thermal forcing for global cooling

Neutral modes of surface temperature and the optimal ocean thermal forcing for global cooling

Habitable Climates: The Influence of Eccentricity

Habitable Climates

Contact Info

Product

Resources

About