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--JACOB SEELEY, describing what happens to Earth's atmosphere during a hothouse climate. Seely and Robin Wordsworth, both of Harvard University, modeled the atmospheric response when sea surface temperatures reached 130[degrees]F, [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2008.11.024 Byline: L.C. Zuchowski, Y.H. Yamazaki, P.L. Read Keywords: Jovian planets; Jupiter; atmosphere; Atmospheres; dynamics Abstract: We have investigated the formation of jet scale meridional circulation cells on Jupiter in response to radiative and zonal momentum forcing. In the framework of semi-geostrophic theory, the meridional streamfunction is described by an elliptic equation with a source term dependent on the sum of the latitudinal derivative of the radiative forcing and the vertical derivative of the zonal momentum forcing. Using this equation with analytic terms similar to the assumed forcing on Jupiter, we obtained two set of atmospheric circulations cells, a stratospheric and a tropospheric one. A possible shift in the overturning circulation of the high and deep atmosphere can be induced by breaking the latitudinal alignment of radiative heating with the enforced belt and zones. A series of numerical simulations was conducted with the Jovian GCM OPUS, which was initiated with observational data obtained from the Cassini CIRS temperature cross-section and a corresponding geostrophic zonal wind field. Newtonian forcing of potential temperature as well as zonal momentum was applied respectively towards latitudinally and vertically uniform equilibrium fields. In accordance with the analytic illustrations two rows of jet scale circulation cells were created. The stratospheric circulation showed the distribution of upwelling over zones and downwelling over belts, consistent with cloud observations. The tropospheric cells featured a partial reversal of the downward vertical velocity over the belts and a considerable reduction of the upward movement over the zones in the domain, consistent with recent detections of high water clouds and lightning in belts. We also used the modeled new forcing fields as source terms for the semi-geostrophic Poisson equation to attribute the origin of the modeled secondary circulation. In this analysis, the stratospheric circulation cells observed in the model are primarily generated in response to radiative forcing, while momentum forcing induces the shifted configurations in the deep atmosphere. Author Affiliation: University of Oxford, Clarendon Laboratory, Parks Road, OX1 3PU Oxford, UK Article History: Received 13 May 2008; Revised 18 November 2008; Accepted 19 November 2008

A thermal model is developed for heating and cooling of an agricultural greenhouse integrated with an aquifer coupled cavity flow heat exchanger system (ACCFHES). The ACCFHES works on the principal of utilizing deep aquifer water available at the ground surface through an irrigation tube well already installed in every agricultural field at constant year-round temperature of 24 [degrees]C. The analysis is based on the energy balance equations for different components of the greenhouse. Using the derived analytical expressions, a computer program is developed in [C.sup.++] for computing the hourly greenhouse plant and room air temperature for various design and climatic parameters. Experimental validation of the developed model is carried out using the measured plant and room air temperature data of the greenhouse (in which capsicum is grown) for the winter and summer conditions of the year 2004-2005 at Chandigarh (31 [degrees]N and 78 [degrees]E), Punjab, India. It is observed that the predicted and measured values are in close agreement. Greenhouse room air and plant temperature is maintained 6-7 K and 5-6 K below ambient, respectively for an extreme summer day and 7-8 K and 5-6 K above ambient, respectively for an extreme winter night. Finally, parametric studies are conducted to observe the effect of various operating parameters such as mass of the plant, area of the plant, mass flow rate of the circulating air and area of the ACCFHES on the greenhouse room air and plant temperature. Keywords: Greenhouse; Aquifer water; Thermal model; Solar energy; Cooling-heating systems

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.07.009 Byline: Erika Kaufmann, Norbert I. Komle, Gunter Kargl Keywords: Ices; Experimental techniques Abstract: Icy surfaces like the polar caps of Mars, comets, Edgeworth-Kuiper belt objects or the surface areas of many moons in the outer Solar System behave different than rock and soil surfaces when irradiated by solar light. The latter ones absorb and reflect incoming solar radiation immediately at the surface. In contrast, ices are partially transparent in the visible spectral range and opaque in the infrared. Due to this fact it is possible for the solar radiation to reach a certain depth and increase the temperature of the sub-surface layers directly. This internal temperature rise is called 'solid-state greenhouse effect,' in analogy to the classical greenhouse effect in an atmosphere. It may play an important role in the energy balance of various icy bodies in the Solar System. Within the scope of a project conducted at the Space Research Institute of the Austrian Academy of Sciences in Graz the solid-state greenhouse effect was investigated experimentally and theoretically. A number of experiments with diverse materials, focussing mainly on layered samples with a surface cover consisting of transparent H.sub.2O-ice, were performed. The samples were irradiated under cryo-vacuum conditions by a solar simulator. The temperature distributions inside the samples were measured and compared with the results of numerical model calculations. We found that the predicted sub-surface temperature maximum is very clearly measurable in glass beads samples with various particle size distributions, but can also be detected in transparent compact surface ice layers. However, in the latter case it is less distinct than originally expected. Measuring the effect by laboratory methods turned out to be a difficult task due to the shallow depth where the temperature maximum occurs. Author Affiliation: Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz, Austria Article History: Received 27 March 2006; Revised 29 June 2006

A numerical study on the runaway greenhouse state is performed by using a general circulation model (GCM) with simplified hydrologic and radiative processes. Except for the inclusion of three-dimensional atmospheric motion, the system utilized is basically equivalent to the one-dimensional radiative-convective equilibrium model of Nakajima et al. in which the runaway greenhouse state is defined. The results of integrations with various values of solar constant show that there exists an upper limit of the solar constant with which the atmosphere can reach a statistical equilibrium state. When the value of solar constant exceeds the limit, 1600 W [m.sup.-2], the atmosphere sets in a 'thermally runaway' state. It is characterized by continuous increase of the amount of water vapor, continuous decrease of the outgoing longwave radiation, and continuous warming of the atmosphere and the ground surface. The upper-limit value of the solar constant obtained by the GCM experiments corresponds to the upper limit of outgoing longwave radiation determined by the one-dimensional model of Nakajima et al. with a fixed value of relative humidity, 60%, which is a typical value obtained by the GCM. The thermally runaway states realized in the GCM are caused by the radiation structure found by Nakajima et al. that prohibits the existence of thermal equilibrium states. The calculated values of the upper limit of radiation and water vapor content cannot be directly applied to describing real planetary atmospheres, since the model physical processes are quite simple-gray radiation scheme without clouds. However, because of this simplification, the GCM gives deeper insight into the structure of a runaway atmosphere.

The industrial and scientific revolutions of the past two centuries have brought much of the physical world under our control. Yet our lives can still be upended by what insurance [...]

The antigreenhouse effect results from a high altitude haze which blocks sunlight while allowing transmission of thermal infrared. An antigreenhouse is observed on Titan and has been proposed for the early Earth. Here, we derive an analytic solution useful for computing the atmospheric and surface temperature with both the greenhouse and antigreenhouse effects included. In agreement with detailed calculations, the analytic solution predicts that a runaway greenhouse on early Titan caused by accretional heat would collapse when the flux fell to 0.9 W [m.sup.-2]. For the present value of the solar luminosity a runaway greenhouse collapses at a geothermal heat flux of 0.4 W [m.sup.-2]. We show that the antigreenhouse effect may compromise attempts to solve the faint young sun problem on the early Earth with a methane-ammonia greenhouse shielded by an organic haze, more than doubling the infrared opacity needed to warm the early Earth compared to the case with no antigreenhouse. Key Words: Titan; atmosphere; greenhouse effect; antigreenhouse effect.

Two models are proposed for evaluating the effects of CO2 emissions on the atmosphere. The models, namely, PAGE and Intera, are used to compute the marginal impact of CO2 emissions and the marginal costs involved in existing CO2 emission reduction policies. Results indicate that existing policies will require an average of $50 to offset the detrimental environmental effect of one ton of CO2.

Climate change policymakers are constrained by uncertainties regarding the avoided costs of climate change and the costs of greenhouse gas emission abatement. These uncertainties may be mitigated by using a sequential approach. The no-regret policy and the innovation process exploitation policy minimize learning time when inertia constraints in the decision process are taken care of.

Technical innovation in energy technologies and systems are induced by need but are restrained by potentially large transitional costs. Nevertheless, it is evident that energy systems accommodate external pressures by adapting slowly over time. A simple integrated model of optimal greenhouse gas abatement over time which incorporates fixed and transitional elements was developed to show that induced technical change and other adaptive responses in energy systems affect climate change assessments and are thus important for abatement policies.

Economists working on integrated assessment models of climate change employ various methods to account for the damages that could result from climate change over a long period and to compare intertemporal costs that would be incurred from greenhouse gas abatement strategies over time. The derived discount rates range from 5% to 8%, implying that even significant damages from climate change will be negligible when considered at present value. In contrast, ethical reasoning yields artificially low discount rates that lead to climate change policies that are inconsistent with most public policy decisions.

This report summarizes discussions on general circulation model studies of climate-chemistry interaction from two workshops whose main objective was to recommend specific general circulation model (GCM) studies of the ozone distribution and the climatic effect of its changes. The workshops also discussed the climatic implications of increasing sulfate aerosols because of their importance to regional climate. The workshops were organized into four working groups: observation of atmospheric [O.sub.3]; modeling of atmospheric chemical composition; modeling of sulfate aerosols; and aspects of climate modeling, Specific recommendations are indicated.

The production of carbon dioxide by industry must be reduced before emissions of greenhouse gases can be controlled, and estimates of the costs of various levels of control are needed. The Energy Modeling Forum's EMF 12 working group used technoeconomic models to study various levels of carbon-dioxide emissions control, including no control, a 50% reduction in emissions and stabilization to 1990 levels. Research indicates that the control of carbon-dioxide emissions may have little effect on global climate change and that market intervention is needed to control emissions.

Three alternative policy instruments used in controlling the accumulation of CO2 and other greenhouse gases in the atmosphere are evaluated. The performance of these policy instruments, namely: the limited policy, the tax policy and the cumulative limit policy, are studiedusing a carbon emission trajectory assessment model. Results reveal that the tax policy instrument is more efficient than its counterparts in controlling CO2 emissions.

Climate modes with enhanced greenhouse gas concentrations have projected temperature increase of 2 ° to 4 °C, winter precipitation increases of up to 15 percent, and summer precipitation decreases of [...]

Surface temperatures over the Arctic Ocean recorded between 1950 and 1990 failed to confirm the atmospheric greenhouse model that predicted a general warming trend for the Arctic. In fact, the Arctic during this time became cooler rather than warmer. Biases that may exist in these temperature records are insufficient to overturn this result. Revised greenhouse models should be based on better knowledge of polar climatic phenomena.