I came across the following essay. Published in 2004, it is still relevant.
The Greenhouse Gas Myth
by Reason McLucus
The debate over human impact on climate is distressing because of the lack of science on both sides of the debate. The scientists involved are behaving more like people involved in political debates than in scientific debates. The debate focuses on superficial issues like average temperature rather than on the amount of heat present. Debaters talk about the amount of carbon dioxide(CO2) in the atmosphere and ignore the possible impact of the heat generated by human activity and the alteration of the thermal characteristics of the physical environment.
This situation is common in human political debates. Another common practice in political debates is looking at only those conditions which appear to validate the arguments of one side or the other rather than looking at all possibilities. Typically this process involves a linear view of relationships. Climate is highly chaotic and cannot be explained as the result of any linear process.
Those who warm of “global warming” claim that humans are increasing average temperatures by increasing the amount of the carbon dioxide in the atmosphere which they claim serves as a global thermostat even though it only constitutes about 0.035% of the atmosphere. Opponents claim if there is any such “warming” that it results solely from increases in the sun’s radiation output even though the earth’s billions of humans add terra calories of heat to the atmosphere daily and have modified the thermal characteristics of the earth’s surface..
The term “global warming” while useful as a political slogan has little scientific value. Average temperatures are as meaningless as the average family size which typically includes a fraction of a person. For example, temperature ranges between 60 and 90 F would have the same average temperature as a range between 50 and 100 F, but the former would be more conducive to biological activity than the latter.
Temperatures can be highly localized. The amount of shade present can affect temperatures as can structures which reflect light or protect an area from the wind. In winter low areas may have lower overnight temperatures than other areas. Areas near water may have higher temperatures. If temperature measurements aren’t taken from all types of areas the measurements may not reflect the actual global averages.
The impact of temperature depends more on the range of temperatures than on the average. For example, plants need temperatures within a particular range. Temperatures that are too cold, particularly below freezing, can cause plants to become inactive or even die. Temperatures that are too high can also inhibit growth or even cause fatal wilting.
Climate depends upon temperature distribution rather than average temperature. Climate in different regions can change with no change in average global temperature. For example, this past summer northwestern Europe suffered from high temperatures while the northeastern United States had cooler than normal temperatures.
The earth normally receives sufficient heat energy from the sun to preclude polar ice fields. The tilt of the earth prevents polar regions from receiving heat directly from the sun during part of the year allowing these regions to become extremely cold. The earth’s heat redistribution system moves some excess heat from tropical regions to polar regions. An increase in such heat movement, such as increased velocity for the Gulf Stream, can reduce ice cover. A decrease in heat movement, such as a blockage in the Gulf Stream’s return flow, could cause an increase in ice cover.
One sub debate involves the question of whether average temperatures were higher in the past than today. Such information cannot be obtained. Physical evidence and human accounts can show the extent to which conditions might have favored plant growth, for example, but not what the average temperature was. Favorable conditions would likely indicate a more moderate range of temperatures rather than temperatures too low or too high for plant growth. The “Medieval Warming Period” may not have been a period of higher average temperatures but a period of moderate weather instead of a period of frigid winters and hot summers.
Those who claim that CO2 plays a controlling role in atmospheric temperature fail to provide a scientific basis for this theory. The theory was originally proposed by Svante Arrhenius. His theory is based on earlier theories about the atom and its relationship with light that were subsequently disproved.[...]
The debate over heating involved the question of whether CO2 or H2O were the primary molecules involved in heating. Arrhenius theorized that CO2 was most important and that changes in the amount of CO2 would produce corresponding changes in ground temperature. An increase in CO2 would increase temperature. A decrease would decrease temperature.
Svante Arrhenius (1859-1927) "On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground" Philosophical Magazine 41, 237-276 (1896) http://webserver.lemoyne.edu/faculty/giunta/ARRHENIUS.HTML[...]
Arrhenius’ theory assumed that the continued absorption of IR would cause heating because the energy wouldn’t be released as radiation. The modern theory suggests that the emission of radiation would cause heating. Such a process is unlikely because individual molecules are unlikely to absorb significant amounts of energy per wave and thus would not release radiation with any significant amount of radiant energy. The initial radiation would carry more energy than the parts of waves absorbed by molecules and re-emitted by individual CO2 molecules. The emission of the same wavelength of radiation from multiple sources creates destructive interference that neutralizes the radiation.
According to thermodynamic theory, each absorption and emission event would result in a very small amount of entropy, the loss of usable energy. The greater the number on times radiation is absorbed and re-emitted, the greater the entropy.
Any radiation emitted by CO2 molecules would only be absorbed by other CO2 molecules rather than by other molecules in the atmosphere. Thus CO2 radiation of IR wouldn’t affect the rest of the atmosphere.
Many of those who support the idea of CO2 as a greenhouse gas may not understand that IR is not a specific wavelength of light, but a very wide spectrum of light. The wavelength and wattage of IR emitted by various substances varies greatly according to the nature and temperature of the substance emitting the radiation. The absorption of radiation by specific chemicals involves specific wavelengths rather than a wide range. IR isn’t the only form of radiation emitted by matter. Engineers are currently working on cameras that detect radiation in the terra hertz range, sometimes called T-rays.
There are other serious problems with the claim that a minor atmospheric chemical can play a major role in regulating planetary temperature. CO2 comprises less than 0.04% of the atmosphere. Earth is generally a poor radiator of energy except for human artifacts.
The very small amount of CO2 means CO2 molecules would have to generate a substantial amount of extra heat to heat the rest of the atmosphere. CO2 has approximately the same specific heat as dry air. Thus each gram of CO2 would have to generate over 2,000 times the amount of heat necessary to heat a gram of CO2.
Water vapor can achieve this ratio because of water’s high specific heat(1.0 - dry air less than 0.25) and high heat of vaporization(540 calories per gram at the boiling point – about 580 at normal temperatures). Condensation of water vapor can release sufficient heat to raise the temperature of air with a mass of over 2,000 times the mass of the water.
This process is particularly important at the dew point, the temperature at which the atmosphere is saturated with water vapor. At this temperature the air normally cannot cool further without the condensation of water vapor. The 540 calories per gram that water vapor must release to condense keeps the air from cooling. The high specific heat of water magnifies this affect.
The combustion of hydrogen in hydrocarbon fuels adds water vapor to the atmosphere. If rainfall doesn’t increase by the same amount as the water added to the atmosphere by human activity then the water vapor content of the air will increase. If this increase raises the dew point above freezing, it will impact the amount of ice/snow cover.
Although the small percentage of CO2 in the atmosphere would limit any warming impact, if there was an impact, once the amount of CO2 reached a sufficient level to absorb all IR in the specific wavelength no more warming [due to CO2] could occur.
Arrhenius and other 19th Century scientists believed that earth needed to radiate as much, or nearly as much, energy back into space as it received from the sun – that is function as a “black body”. Some scientists confuse the rock and water portion of the planet with the planet itself. The gaseous envelop that surrounds the planet is just as much a part of the planet as is the rock and water portion. Solar radiation that reaches the earth’s surface must penetrate miles of relatively dense atmosphere to heat the “interior” of the planet.
A biologically active planet like earth must use a significant portion of the energy it receives from the sun to fuel biological life. Plants convert sunlight into the chemical bonds used to produce plant structure. Plants in turn provide energy to animals that eat portions of the plants. Solar energy is also used to “do work” by evaporating water and then moving water vapor from the oceans deep inland to provide water for biological life. Entropy occurs at each energy transition stage.
The rock and water portion of earth is actually a poor radiator. Water like other transparent substances is a poor radiator because it is a poor absorber. Water generally releases heat through evaporation rather than radiation. Plants, which cover much of the rock, are ineffective radiators. Much of the energy they absorb is used to “do work” by growing the plant rather than to produce heat. Plants tend to be crowded together and radiation is more likely to be intercepted by other plants or other parts of the same plant than to be radiated toward space. Plants tend to release excess heat through evaporation of water rather than radiation because evaporation cools the plant faster than radiation would.
Desert sands tend to be poor radiators because they reflect much of the radiation back into space rather than absorbing it all and heating up.
Many human artifacts are good radiators. Black asphalt pavement is a particularly good absorber and radiator of solar energy. Buildings also may absorb and radiate heat well. Reflective glass buildings reflect radiation back and significantly increase heating of the air if several are in close proximity.
Mechanical devices directly heat the air as well as produce radiation. Outdoor lights radiate visible light into space as well as IR. Human beings are themselves good radiators. A human will stand out like a beacon against a natural background when viewed through IR sensitive cameras.
The subject of climatic change needs some real science to replace the believe in atmospheric gases with magical powers. In addition to the issue of how changes in solar radiation affect global heating, science should examine issues such:
1. The amount of heat energy present on the planet rather than looking at superficial atmospheric temperature;
2. How heat generated by humans affects the amount of heat energy present in the system and how human artifacts affect heating on the rock surface;
3. The role of conduction and convection in redistributing heat energy among different areas as well as moving heat upward through the atmosphere;
4. The role of water vapor in moving heat around on the earth’s surface and moving heat from the rock and water portion of the planet upward through the atmosphere.
Although the earth’s interior is hot, the sun is responsible for heating the surface and atmosphere. Changes in solar radiation received are likely to cause different temperatures, but this impact is likely to involve a complex equation. Changes in solar radiation may not cause the same percentage change in earth’s temperature.
For example, the polar ice feedback loops may magnify the impact of changing radiation levels on temperature. As radiation increases, the area covered by ice declines causing less reflection of solar radiation back into space resulting in increased heating. As heating increases more ice melts, etc. Conversely reduced radiation means less melting and increased ice cover causing more reflection of radiation back into space lowering temperatures and further reducing melting.
1. Heat Energy Present
Looking only at atmospheric temperatures cannot provide an accurate measure of the amount of heat energy present on the planet. For example, an area with lower air temperature may actually have more heat energy than an area of higher temperature if the air in the cooler area has a higher water content. Water vapor has more heat energy than dry air because of water’s high heat of vaporization and higher coefficient of heat than dry air.
The relative amount of solid, liquid and gaseous water on the planet needs to be examined. Water’s heat of fusion of 80 calories per gram means that liquid water contains significantly more heat than frozen water. Thus the melting of polar ice caps means the planet contains more heat energy.
Soil and water temperature increases will cause eventual increases in air temperatures depending on the process of heat transfer to the atmosphere.
2. Direct Human Impact on Temperature
Humans generate substantial amounts of heat. Human artifacts can also affect temperatures. Scientists have known about urban heat islands for years. Cities may have temperatures as much as 10 degrees F higher than the surrounding countryside.
Asphalt roads are good radiation absorbers that also radiate well. Roads and buildings also transfer heat energy directly to the air through conduction. Plants are good absorbers of radiation, but they convert radiation into the chemical bonds of organic molecules rather Replacing plants, especially trees with roads and buildings increases heating.
Another way in which humans can increase heating isn’t as obvious. Cold blooded animals in water absorb heat from solar radiation and the surrounding water. Thus a reduction in the ocean’s fish population could increase water temperature and eventually air temperature.Human induced changes in water composition may also impact temperature by changing the rate at which water transfers heat to atmosphere.
3. Conduction and Convection
Those who talk about global warming emphasize energy transfer through radiation, but conduction and convection play a more important role in redistributing heat energy including heating the air. Conversion of heat energy into radiation is fixed according to the temperature and radiative characteristics of the radiating substance.
Conduction is potentially much faster because it depends on the relative differences in temperatures of the substances exchanging heat energy as well as their heat coefficients. A human body will lose heat faster in cold water than in cold air because water has a higher coefficient of heat than air. Water must absorb more heat to change its temperature.
As water and rock heat up from absorption of solar radiation they immediately begin heating the air in thermal contact. That heated air then rises because air becomes lighter in weight as it warms. Cooler air falls to the surface and begins warming.
Even highly radiative surfaces like asphalt roadways transmit significant amounts of heat energy to air through conduction. The “heat waves” rising from such surfaces are caused by conductive heating of the air by the roadway. On a sunny day partially exposed sections of roadway will conduct sufficient heat energy to ice covered areas to cause melting and evaporation of some of that ice even when air temperatures are below freezing.
Movement of large air masses can transfer heat from hotter areas to colder areas. Movement of cold air masses can cause cooling of surfaces in areas that had been warmer by increasing conduction of heat to the air.
4. Role of Water in Moving Heat
The Gulf Stream and other ocean currents move heat from tropic areas to colder regions. Water vapor plays a major role in moving heat from the surface up through the atmosphere.
Traditional physics has taught that the primary forms of heat transfer are conduction, convection and radiation. Evaporation is a fourth method of heat transfer. Evaporation transfers substantial amounts of heat from bodies of water, biological life and water covered solids to the atmosphere. Plants evaporate water from their leaves to release excess heat. Animals release heat through exhaling water vapor. Humans and some other animals lose water through the skin which then evaporates into the air.
As water vapor moves upward through the atmosphere it takes that heat with it. The condensation of that vapor in the atmosphere to form clouds releases this heat. In warm areas, some of this heat energy is converted into electrical discharges including discharges above the clouds called by such names as “sprites” and “blue jets”.
Clouds have a mixed impact on earth’s temperature. They reflect solar radiation back into space to reduce heating of the surface. Clouds also prevent air from rising and thus hold heated air closer to the surface.The amount of water vapor in the atmosphere determines the minimum air temperature. The dew point is the temperature at which the air is so saturated with water vapor that some of it must condense out of the air. At ground level the air temperature normally will not drop below the dew point. Thus if the water vapor content of the air increases so will the average minimum temperature. The impact is most important from late fall through early spring. An increase in the number of days in which the dew point is above freezing reduces freezing and increases melting of ice. Northern waterways may freeze over later and resume flow earlier.
Original - http://reasonmclucus.tripod.com/CO2myth.html