scholarly journals Greenhouse effect dependence on atmospheric concentrations of greenhouse substances and the nature of climate stability on Earth

2002 ◽  
Vol 2 (2) ◽  
pp. 289-337 ◽  
Author(s):  
V. G. Gorshkov ◽  
A. M. Makarieva

Abstract. Due to the exponential positive feedback between sea surface temperature and saturated water vapour concentration, dependence of the planetary greenhouse effect on atmospheric water content is critical for stability of a climate with extensive liquid hydrosphere. In this paper on the basis of the law of energy conservation we develop a simple physically transparent approach to description of radiative transfer in an atmosphere containing greenhouse substances. It is shown that the analytical solution of the equation thus derived coincides with the exact solution of the well-known radiative transfer equation to the accuracy of 20% for all values of atmospheric optical depth. The derived equation makes it possible to easily take into account the non-radiative thermal fluxes (convection and latent heat) and obtain an analytical dependence of the greenhouse effect on atmospheric concentrations of a set of greenhouse substances with arbitrary absorption intervals. The established dependence is used to analyse stability of the modern climate of Earth. It is shown that the modern value of global mean surface temperature, which corresponds to the liquid state of the terrestrial hydrosphere, is physically unstable. The observed stability of modern climate over geological timescales is therefore likely to be due to dynamic singularities in the physical temperature-dependent behaviour of the greenhouse effect. We hypothesise that such singularities may appear due to controlling functioning of the natural global biota and discuss major arguments in support of this conclusion.

2013 ◽  
Vol 53 (A) ◽  
pp. 832-838
Author(s):  
Smadar Bressler ◽  
Giora Shaviv ◽  
Nir J. Shaviv

We present a radiative transfer model for Earth-Like-Planets (ELP). The model allows the assessment of the effect of a change in the concentration of an atmospheric component, especially a greenhouse gas (GHG), on the surface temperature of a planet. The model is based on the separation between the contribution of the short wavelength molecular absorption and the long wavelength one. A unique feature of the model is the condition of energy conservation at every point in the atmosphere. The radiative transfer equation is solved in the two stream approximation without assuming the existence of an LTE in any wavelength range. The model allows us to solve the Simpson paradox, whereby the greenhouse effect (GHE) has no temperature limit. On the contrary, we show that the temperature saturates, and its value depends primarily on the distance of the planet from the central star. We also show how the relative humidity affects the surface temperature of a planet and explain why the effect is smaller than the one derived when the above assumptions are neglected.


2021 ◽  
pp. 152808372110142
Author(s):  
Ariana Khakpour ◽  
Michael Gibbons ◽  
Sanjeev Chandra

Porous membranes find natural application in various fields and industries. Water condensation on membranes can block pores, reduce vapour transmissibility, and diminish the porous membranes' performance. This research investigates the rate of water vapour transmission through microporous nylon and nanofibrous Gore-Tex membranes. Testing consisted of placing the membrane at the intersection of two chambers with varied initial humidity conditions. One compartment is initially set to a high ([Formula: see text]water vapour concentration and the other low ([Formula: see text], with changes in humidity recorded as a function of time. The impact of pore blockage was explored by pre-wetting the membranes with water or interposing glycerine onto the membrane pores before testing. Pore blockage was measured using image analysis for the nylon membrane. The mass flow rate of water vapour ( ṁv) diffusing through a porous membrane is proportional to both its area (A) and the difference in vapour concentration across its two faces ([Formula: see text], such that [Formula: see text] where K is defined as the moisture diffusion coefficient. Correlations are presented for the variation of K as a function of [Formula: see text]. Liquid contamination on the porous membrane has been shown to reduce the moisture diffusion rate through the membrane due to pore blockage and the subsequent reduced open area available for vapour diffusion. Water evaporation from the membrane's surface was observed to add to the mass of vapour diffusing through the membrane. A model was developed to predict the effect of membrane wetting on vapour diffusion and showed good agreement with experimental data.


2021 ◽  
Vol 56 (1-2) ◽  
pp. 635-650 ◽  
Author(s):  
Qingxiang Li ◽  
Wenbin Sun ◽  
Xiang Yun ◽  
Boyin Huang ◽  
Wenjie Dong ◽  
...  

2021 ◽  
Author(s):  
Maximilian May ◽  
Nils Weitzel ◽  
Lukas Jonkers ◽  
Kira Rehfeld

<p>Global mean surface temperature is a fundamental measure for climate evolution in both past and present and a key quantity to evaluate climate simulations. However, for paleoclimate periods, its calculation hinges on proxy data distributed sparsely and inhomogeneously in both space and time. Thus, large sets of different proxy records need to be combined in order to obtain global mean temperature reconstructions, but there is no widely accepted method to perform this task. Building on the work of [1], we suggest and evaluate an algorithm to reconstruct spatially averaged surface temperatures on centennial to orbital timescales. As the most abundant archive for continuous temperature reconstructions, we focus on marine sediment records as input data. Our implementation is applicable to any compilation of sea-surface temperature reconstructions and capable of calculating global, hemispherical and regional temperature. Major steps of the reconstruction algorithm are interpolation to a common timescale, zonal normalization and calculation of spatially weighted sums, including uncertainty propagation via Monte Carlo methods. We assess the applicability of the algorithm by employing it to the PalMod130k marine palaeoclimate data synthesis [2] and to pseudo-proxy data generated from transient simulations of the last glacial cycle. Our results suggest that the algorithm is capable of calculating average temperatures mostly consistent with expectations, however capturing centennial-scale variability is limited due to the low spatio-temporal distribution of the input data. This underlines the importance of both increasing the amount, resolution and age control of proxy data as well as extending the algorithm such that it also incorporates other types of paleoclimate archives.</p><p> </p><p>References:</p><p>[1]  C. W. Snyder, “Evolution of global temperature over the past two million years,” Nature, vol. 538, no. 7624, pp. 226–228, 2016</p><p>[2]  L. Jonkers, O. Cartapanis, M. Langner, N. McKay, S. Mulitza, A. Strack, and M. Kucera, “Integrating palaeoclimate time series with rich metadata for uncertainty modelling:  Strategy and documentation of the PALMOD 130k marine palaeoclimate data synthesis,” Earth System Science Data, vol. 12, no. 2, pp. 1053–1081, 2020</p>


2021 ◽  
Author(s):  
Shujiro Komiya ◽  
Fumiyoshi Kondo ◽  
Heiko Moossen ◽  
Thomas Seifert ◽  
Uwe Schultz ◽  
...  

<p>Commercially available laser-based spectrometers permit continuous field measurements of water vapour (H<sub>2</sub>O) stable isotope compositions, yet continuous observations in the Amazon, a region that significantly influences atmospheric hydrological cycles on regional to global scales, are largely missing. In order to achieve accurate on-site observations in such conditions, these instruments will require regular on-site calibration, including for H<sub>2</sub>O concentration dependence ([H<sub>2</sub>O]-dependence) of isotopic accuracy.</p><p>With the aim of conducting accurate continuous δ<sup>18</sup>O and δ<sup>2</sup>H on-site observation in the Amazon rainforest, we conducted a laboratory experiment to investigate the performance and determine the optimal [H<sub>2</sub>O]-dependence calibration strategy for two commercial cavity-ring down (CRDS) analysers (L1102i and L2130i models, Picarro, Inc., USA), coupled to our custom-built automated calibration unit. We particularly focused on the rarely investigated performance of the instruments at atmospheric H<sub>2</sub>O contents above 35,000 ppm, a value regularly reached at our site.</p><p>The later analyser model (L2130i) had better precision and accuracy of δ<sup>18</sup>O and δ<sup>2</sup>H measurements with a less pronounced [H<sub>2</sub>O]-dependence compared to the older L1102i. The [H<sub>2</sub>O]-dependence calibration uncertainties did not significantly change with calibration intervals from 28 h up to 196 h, suggesting that one [H<sub>2</sub>O]-dependence calibration per week for the L2130i and L1102i analysers is enough. This study shows that with both CRDS analysers, correctly calibrated, we should be able to discriminate natural diel, seasonal and interannual signals of stable water vapour isotopes in a tropical rainforest environment.</p><p> </p>


2017 ◽  
Vol 13 (8) ◽  
pp. 1037-1048 ◽  
Author(s):  
Henrik Carlson ◽  
Rodrigo Caballero

Abstract. Recent work in modelling the warm climates of the early Eocene shows that it is possible to obtain a reasonable global match between model surface temperature and proxy reconstructions, but only by using extremely high atmospheric CO2 concentrations or more modest CO2 levels complemented by a reduction in global cloud albedo. Understanding the mix of radiative forcing that gave rise to Eocene warmth has important implications for constraining Earth's climate sensitivity, but progress in this direction is hampered by the lack of direct proxy constraints on cloud properties. Here, we explore the potential for distinguishing among different radiative forcing scenarios via their impact on regional climate changes. We do this by comparing climate model simulations of two end-member scenarios: one in which the climate is warmed entirely by CO2 (which we refer to as the greenhouse gas (GHG) scenario) and another in which it is warmed entirely by reduced cloud albedo (which we refer to as the low CO2–thin clouds or LCTC scenario) . The two simulations have an almost identical global-mean surface temperature and equator-to-pole temperature difference, but the LCTC scenario has  ∼  11 % greater global-mean precipitation than the GHG scenario. The LCTC scenario also has cooler midlatitude continents and warmer oceans than the GHG scenario and a tropical climate which is significantly more El Niño-like. Extremely high warm-season temperatures in the subtropics are mitigated in the LCTC scenario, while cool-season temperatures are lower at all latitudes. These changes appear large enough to motivate further, more detailed study using other climate models and a more realistic set of modelling assumptions.


2014 ◽  
Vol 32 (3) ◽  
pp. 207-222 ◽  
Author(s):  
V. Barabash ◽  
A. Osepian ◽  
P. Dalin

Abstract. Mesospheric water vapour concentration effects on the ion composition and electron density in the lower ionosphere under quiet geophysical conditions were examined. Water vapour is an important compound in the mesosphere and the lower thermosphere that affects ion composition due to hydrogen radical production and consequently modifies the electron number density. Recent lower-ionosphere investigations have primarily concentrated on the geomagnetic disturbance periods. Meanwhile, studies on the electron density under quiet conditions are quite rare. The goal of this study is to contribute to a better understanding of the ionospheric parameter responses to water vapour variability in the quiet lower ionosphere. By applying a numerical D region ion chemistry model, we evaluated efficiencies for the channels forming hydrated cluster ions from the NO+ and O2+ primary ions (i.e. NO+.H2O and O2+.H2O, respectively), and the channel forming H+(H2O)n proton hydrates from water clusters at different altitudes using profiles with low and high water vapour concentrations. Profiles for positive ions, effective recombination coefficients and electrons were modelled for three particular cases using electron density measurements obtained during rocket campaigns. It was found that the water vapour concentration variations in the mesosphere affect the position of both the Cl2+ proton hydrate layer upper border, comprising the NO+(H2O)n and O2+(H2O)n hydrated cluster ions, and the Cl1+ hydrate cluster layer lower border, comprising the H+(H2O)n pure proton hydrates, as well as the numerical cluster densities. The water variations caused large changes in the effective recombination coefficient and electron density between altitudes of 75 and 87 km. However, the effective recombination coefficient, αeff, and electron number density did not respond even to large water vapour concentration variations occurring at other altitudes in the mesosphere. We determined the water vapour concentration upper limit at altitudes between 75 and 87 km, beyond which the water vapour concentration ceases to influence the numerical densities of Cl2+ and Cl1+, the effective recombination coefficient and the electron number density in the summer ionosphere. This water vapour concentration limit corresponds to values found in the H2O-1 profile that was observed in the summer mesosphere by the Upper Atmosphere Research Satellite (UARS). The electron density modelled using the H2O-1 profile agreed well with the electron density measured in the summer ionosphere when the measured profiles did not have sharp gradients. For sharp gradients in electron and positive ion number densities, a water profile that can reproduce the characteristic behaviour of the ionospheric parameters should have an inhomogeneous height distribution of water vapour.


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