The Martian paleoclimate and enhanced atmospheric carbon dioxide

Current evidence indicates that the Martian surface is abundant with water presently in the form of ice, while the atmosphere was at one time more massive with a past surface pressure of as much as 1 atm of CO₂. In an attempt to understand the Martian paleoclimate, we have modeled a past CO₂H₂O greenhouse and find global temperatures which are consistent with an earlier presence of liquid surface water, a finding which agrees with the extensive evidence for past fluvial erosion. An important aspect of the CO₂H₂O greenhouse model is the detailed inclusion of CO₂ hot bands. For a surface pressure of 1 atm of CO₂, the present greenhouse model predicts a global mean surface temperature of 294°K, but if the hot bands are excluded, a surface temperature of only 250°K is achieved.     

An analysis of the strong zonal circulation within the stratosphere of Venus

A dynamical model is presented for the observed strong zonal circulation within the stratosphere of Venus. The model neglects rotational effects and considers a compressible and radiating atmosphere. It is shown that diurnal radiative heating is negligible within the lower stratosphere, a region below 85km, while observational evidence for the strong zonal circulation pertains to the lower stratosphere within which a direct thermal driving for the circulation is absent. The analysis, however, suggests that propagating internal gravity waves generated by diurnal solar heating of the upper stratosphere induce mean zonal velocities within the upper and lower stratosphere.Considering the linearized equations of motion and energy, and following Stern's (1971) analysis for an analogous problem, it is shown that the zonal velocity induced by internal gravity waves is retrograde in direction, a result which is in agreement with observation. The nonlinear equations of motion and energy are then solved by an approximate analytical method to determine the magnitude of the zonal velocity. This velocity increases from zero at the tropopause to about 200 msec^?1 at the 85 km level. The velocity near the uv-cloud level compares favorably with the observed value of 100 msec^?1.     

A commentary on the recent CO2-climate controversy

Suggestions have persisted over the past few years that, contary to conventional estimates, increasing levels of atmospheric carbon dioxide will produce negligible warming of the earth's surface, or might even result in surface cooling. In the present paper we reexamine several aspects of these suggestions and illustrate that they are either founded in various violations of the first law of thermodynamics, or that they are based upon misinterpretations of historical data.     

The effects of scattering and conduction upon radiative transfer in lunar and mercurian surfaces

The linearized analysis of Cess and Srinivasan (1971) for thermal emission from lunar and Mercurian surfaces following a sudden eclipse has been extended to include two additional factors. One is the separate influence of scattering upon the radiative transport process within the surface material. The second is the effect of thermal conduction as an additional energy transport mechainsm.     

The influence of ethane and acetylene upon the thermal structure of the Jovian atmosphere

Ethane and acetylene, both of which possess more efficient emission bands than methane, have been incorporated into a thermal structure model for the atmosphere of Jupiter. Choosing for illustrative purposes the mixing ratios $\text{[}\text{C}{}_2\text{H}{}_6\text{]}\text{[}\text{H}{}_2\text{]}\text{= 10}{}^{\mathrm{?5}}$ and $\text{[}\text{C}{}_2\text{H}{}_2\text{]}\text{[}\text{H}{}_2\text{]}\text{= 5 × 10}{}^{\mathrm{?7}}$, it is found that these hydrocarbon gases lower the atmospheric temperature within the thermal inversion region by as much as 20 K, subsequently reducing the emission intensity of the 7.7 μm CH₄ band below the observed result. It is qualitatively shown, however, that this cooling by C₂H₆ and C₂H₂ could be compensated by aerosol heating resulting from a uniformily mixed aerosol which absorbs 15% of the incident solar radiation. Such aerosol heating has been suggested by uv albedo observations.     

A Saturnian stratospheric seasonal climate model

Motivated by recent observational evidence that seasonal processes occur within Saturn's stratosphere, we have constructed a seasonal stratospheric climate model. This model predicts stratospheric temperatures, above the P = 0.1-atm level, as a function of time throughout the Saturnian year. Specific results are presented for South-polar and equatorial temperatures. The model predicts that substantial seasonal phase lags exist; maximum stratospheric temperatures at the South pole occur at the Southern Hemisphere's autumnal equinox. Brightness temperature observations at 17.8 μm, taken during 1977/1978, indicate that stratospheric temperatures are greater at the South pole than at the equator. The model is consistent with these observations, predicting enhanced South-polar temperatures, relative to the equator, from 1975 to 1983.     

Latitudinal variations in Jovian stratospheric temperature

Ground-based observations of Jupiter show that the planet's stratospheric and tropospheric thermal emission are anticorrelated. The observations can possibly be explained by latitudinal variations in cloud altitude. These variations cause differential stratospheric heating by sunlight which is reflected off the clouds and then absorbed within the stratosphere by visible and near-infrared bands of methane.     

A model for the temperature inversion within the atmosphere of Saturn

A model for the temperature inversion within the atmosphere of Saturn is proposed and is shown to be consistent with photometric data in the 17- to 25-μm region. The proposed model incorporates solar heating by some “aerosol,” with the aerosol heating per unit mass of the atmosphere being uniformly distributed throughout that portion of the atmosphere overlying the upper cloud deck. For a methane-to-hydrogen mixing ratio of 7 × 10^?4, the model results suggest that 20% of the incident solar radiation is absorbed by the aerosol, while this is reduced to 16% for an enhanced methane mixing ratio of 2.1 × 10^?3.     

A clarification of certain issues related to the CO2—Climate problem

In this paper we examine and clarify several arguments that have been put forth by Dr. S. B. Idso in an article appearing within this issue of Climatic Change.