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LJWorld.com weblogs Science Becoming Religion

Venus Not an Example of Greenhouse Gas Effect

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Global warming groups falsely claim Venus provides an example of what they call the greenhouse gas effect. According to the greenhouse gas theory, the sun heats the surface of a planet and the atmosphere prevents infrared radiation (IR) from leaving which causes heating. Even if the theory about "trapping" had not been disproved in 1909 by [R. W. Wood][1] , the sun cannot be heating the surface of Venus to a [temperature][2] of 460 C.

Mercury's surface [temperature][3] only reaches 425 C and it is closer to the sun. Mercury's surface doesn't have an atmosphere that reflects 75% of the incoming solar radiation like Venus has. Thus solar radiation cannot be causing the high temperature of Venus. The surface of Venus even receives less solar radiation than earth's surface.

If the sun were heating Venus, there should be a temperature gradient with the highest temperature in the daylight area and the lowest temperature on the night area. Instead the temperature is the same in both areas as well as the [same][4] at the poles and the equator.

The only plausible explanation is that there is no significant heat input from outside. The atmosphere of Venus is more likely to be hot because the solid portion of the planet is hot and distributes that heat uniformly to the surface.

One explanation could be that Venus has a greater amount of radioactive material somewhere below its surface. Earth has deposits of uranium, but they are dispersed and produced no real heating of the surrounding material. Venus could have begun with much larger deposits that heated the subsurface areas for a long period of time.

Those who believe in greenhouse gases generally don't understand that earth's surface cools (loses heat) primarily by transferring heat energy to the atmosphere rather than by converting it to radiation. The surface conducts heat to the atmosphere through direct contact with the air.

Bodies of water transfer heat to the atmosphere through the evaporation of water. The ground can also transfer heat energy to the air through evaporation of water. Each gram of water that evaporates takes sufficient heat to reduce the temperature of 540 grams of water by 1 C. This process doesn't necessarily raise the temperature of the atmosphere except that wet air cools slower than dry air.

Greenhouse gas believers tend to ignore the fact that a significant portion of solar energy on earth is stored by plants as the electron bonds holding sugars and other complex carbon molecules together. Plants are not present on Venus to perform this function.

Gravity cools earth's atmosphere. Heat is the kinetic energy or motion of atoms/molecules. Any object attempting to move away from earth's surface whether it's a ball or a water molecule has part of its kinetic energy converted to potential energy. As air molecules move away from the surface they slow down and thus cool. When objects fall back to earth the potential energy is reconverted to kinetic energy, but for air molecules this energy is usually the kinetic energy of the air mass rather than the energy of individual molecules. Only rarely is the potential energy converted to heat energy such as in the [Chinook][5] wind along the east slope of the Rockies or the [heat bursts][6] associated with the collapse of thunderstorms.

On earth, high air pressure such as a [Bermuda High][7] and clouds can prevent heated air from cooling by rising. Venus has clouds that block heated air from rising and air pressure much higher than that of a Bermuda High.

Air doesn't convert heat to radiation very well so it doesn't cool significantly by producing radiation. Radiation by solids depends upon physical characteristics of the material. For example, dark material produces more radiation that light material. Scientists have insufficient data about the surface of Venus to determine how well it converts heat energy to radiation.

A common misconception about heat is that it can be "trapped". That would only be possible if heat were a fluid as Ben Franklin believed. Only heated matter such as gas molecules can be trapped. Greenhouses don't trap heat itself. They trap heated air.

The uniformity of temperature is not the only way Venus differs from other planets. Its rotation on its axis is clockwise which is the reverse of earth and other planets. Other large planets have moons but Venus does not. Venus doesn't have as many impact craters as other bodies including earth's moon. The atmosphere is mostly carbon dioxide instead of an oxygen / nitrogen mix like earth. Venus lacks atmospheric and surface water and its clouds are comprised of sulfuric acid.

All of these conditions could be explained by a single event in the planet's relatively recent past, possibly within the last few hundred million years.

Dr. J Huw Davies of the School of Earth and Ocean Sciences at Cardiff University in the U.K. believes Venus once suffered a head on [collision][8] with another large body in its early history. He believes such a collision could have caused Venus to reverse its rotation.

What if such a collision occurred relatively recently and involved a body coming from the direction of the sun on a comet like trajectory? Such a body would have been very hot and moving at high speed to escape the sun's gravitational pull.

To reverse Venus rotation the body would have needed to hit Venus off center and at an angle so that the force would be applied opposite to the Venus direction of rotation.

The body could have been soft if not molten from passing close to the sun. The high speed collision with Venus would have generated heat for the body and Venus.

Instead of a hard impact that might have dislodged a piece of Venus to form a moon (the process many believe produced earth's moon), the body would have spread over the surface of Venus at a high velocity. This process

Comments

Stu Clark 2 years, 11 months ago

It's hard to know where to begin to critique this piece. The sun has to be an important determinant of Venus' temperature. To assert otherwise is nonsensical. While it is true that there is no net inflow of heat from the sun, the 25% of solar energy that is absorbed must be re-emitted out to space.

The physics is that the spectral radiance of an object is a function of its temperature (Planck). So the sun emits a lot of short wave radiation which must then be re-emitted by Venus as long wave. Many gases, CO2, water vapor, methane, while transparent to the short wave energy, absorb in the long wave region. This forms a resistance to the radiative heat flow to space. An increase in this resistance will not result in heat being "trapped", but it will cause the temperature of the radiating material to increase. In other words, the temperature of the radiating material must rise to push the same amount of heat through the increased resistance.

The same rules apply to the Earth. This article goes into a lot of speculation on other sources of heat, convection, and so on, but the ultimate heat loss from a planet is 100% by radiation. Increasing the resistance of this path will, all other things being equal, work to increase the temperature of the planet's surface and atmosphere.

The "all other things being equal" is important stipulation. Climate is the outcome of a complex set of conditions. Hence the ambiguity that allows some to claim that climate change is a non-event without sounding totally nuts.

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Reason McLucus 2 years, 10 months ago

The idea that heat "flows" as radiation is a variation of the long discredited theory proposed by Ben Franklin that heat involved some type of "fluid". The current view of heat energy is that heat is the kinetic energy or motion of atoms/molecules. Heat energy does not need to "flow into space" to cease being heat energy. In the atmosphere some of the kinetic energy of individual air molecules is converted into the kinetic energy of air masses. A major cause of the slowing. or cooling, of air molecules is the conversion of the kinetic energy of air molecules into potential energy by gravity as air molecules move away from the ground. Energy is also essentially "lost" through the process of entropy which represents the fact that no energy transfer or conversion is 100% efficient.

Incidentally, the correct terms for the wavelength of infrared is "near", "mid" and "far". the wavelength of IR is measured in microns (a millionth of a meter) which is a very short distance. The term "long wave" in electromagnetic radiation is more accurately applied to some radio waves.

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Stu Clark 2 years, 10 months ago

For one thing radiant heat does flow. The flow is made up of photons, the smallest quanta of electromagnetic radiation. No transport fluid is needed. These photons have a range of energies. In the kind of work that I do, we are generally concerned with just two energy bands, the visible light band which typifies most of the sun's emission and the IR band typifying the heat emitted from bodies around room temperature and below. We typically do not subdivide these bands.

For another, your explanation violates the conservation of energy principle. Heat energy flowing into space does not cease to be heat energy. The photons simply travel at light speed until they hit an object where they are either absorbed, transferring energy to the object, or reflected. If the object is in thermal equilibrium, the heat radiated out must equal the amount absorbed. Entropy does not enter into the equation.

Your rationale regarding atmospheric molecules is interesting but irrelevant to the heat balance of the object. The surface of the moon has a temperature but no atmosphere at all. The point of the greenhouse analogy is that some of the Earth's atmospheric gases are absorptive in the IR range. See my August 29 post (which should have qualified "absorbing gas" as "IR absorbing gas").

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devobrun 2 years, 11 months ago

And none of it is science.

Science requires experiment. The test.

And all the hypotheses in the world cannot make science, unless an experiment is done.

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Paul Decelles 2 years, 11 months ago

@CA,

I agree with you. But the original post shows a common rhetorical trick used to "debate" science and that is to set up a straw man. For example the poster is wrong in the assertion

"Greenhouse gas believers tend to ignore the fact that a significant portion of solar energy on earth is stored by plants as the electron bonds holding sugars and other complex carbon molecules together. Plants are not present on Venus to perform this function."

About the only thing that is most certainly correct in this assertion is that plants are not present on Venus, though Devo might argue that until we do some sort of experiment, we are just making up stuff. From what I have seen in numerous articles, climate scientists do attempt to incorporate photosynthesis into modeling of the carbon cycle. The problem is that the effect of increasing carbon dioxide on plant growth and on large scale ecosystems is not as straightforward as one might think.

It is one thing to argue about why you think global warming is happening (or not) but there ought to be at least a modicum of scientific reasoning used if you are going to argue the science.

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Stu Clark 2 years, 11 months ago

Well, OK, but spectral radiation from the sun and from Venus has been measured. The radiative properties of various gases have also been measured. So we should not need more experiments to determine these, nor the 4th power radiation relationship between heat flow and temperature. Given this, I can make a simple radiative model and show that Increasing the amount of absorbing gas in an atmosphere will cause the planet temperature to increase as well. That much is based on proven physics.

My only point is that the author was is error in dismissing the effect of "greenhouse" gases.

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