I actually started to write about lightning, and went to my old textbooks to get the exact scientific terminology for the mechanisms at play, and happened across a very interesting section about carbon dioxide in my Chemistry 101 text. The book, “Chemistry: the central science,” was published in 1977. It was the required text for the required chemistry course for all freshman engineering students in 1979. A little research reveals the authors Lemay and Brown have continually updated it, keeping it one of the prominent chemistry texts in engineering schools. There, on page 301, began the section: Water Vapor, Carbon Dioxide, and Climate I had recently had an email discussion with a friend from the neighborhood about the climate crisis, as he sits firmly in the camp of disbelief. So I read with interest to make sure I had accurately represented scientific phenomena well. It turns out I did an OK job, but was unclear or not specific enough about the interplay of infrared radiation and CO2. Backtracking a little, I should cover the fundamentals. The book says it well:
We have seen how the atmosphere makes life as we know it possible on earth by screening out harmful short-wavelength radiation. In addition, the atmosphere is essential in maintaining a reasonably uniform and moderate temperature on the surface of the planet. The two atmospheric components of major importance in maintenance of the earth’s surface temperature are carbon dioxide and water.
In other words, the upper atmosphere absorbs and reflects high-frequency radiation from the sun that would kill us all, like x-rays and gamma-rays, and CO2 and water are the primary temperature regulators of the planet’s surface temperature. It continues:
About 71 percent of all solar radiation that strikes the outer atmosphere is eventually absorbed by the planet. The remainder is reflected back out into space. The temperature of the planet as seen from outer space is determined by the amount of absorbed energy. The maximum in intensity of solar radiation occurs in the visible portion of the spectrum. Because the earth’s atmoshpere is reasonably transparent in this region of the spectrum, most absorption of solar radiation takes place at the earth’s surface.
So, most of the radiation from the sun is in the range of frequencies we consider “light.” As this energy strikes the surface, it is absorbed. We know that the rate of absorption depends on a lot of things, like mass and reflectivity of the surface material. For example, given similar surface areas and thicknesses, black concrete absorbs more energy than white ice, which would reflect more of the radiation striking it. This is known as the albedo effect. The color and “heat capacity,” (a function of mass) of all materials on the surface affect the absorption of radiation.
Like all bodies in space, the earth radiates energy back into space at the same rate it absorbs energy from the sun. This is known as being in thermal balance. The radiation emitted by earth is within the infrared radiation range of frequencies (you can think of them as a spectrum of colors) due to the temperature of the earth. While the atmosphere is relatively transparent to visible light, it is not transparent to infrared radiation. Water vapor and carbon dioxide absorb infrared waves emanating from the surface. Water vapor’s absorption of infrared rays keeps the nighttime low temperatures relatively close to the daily high temps when the surface is emitting radiation but receiving none from the sun. This stabilizing or radiation-capturing phenomenon is starkly apparent when virtually no water vapor is present to absorb the infrared emanating from the surface, such as in dry desert areas, where it can be extremely hot during the day, yet very cold at night. The concentration of water vapor varies from place to place over time, but only close to the surface. As elevation increases, air density decreases, so potential maximum concentration of water vapor decreases. The water vapor concentration at 30km altitude in the stratosphere is only 3 parts per million. CO2, however, gets distributed and suspended evenly throughout the atmosphere.
According to a study the authors cite (Update: Peer reviewed reference on figure 10.13 “(After B. Bolin and W. Bischof, Tellus, 22, 431, 1970)”) that was published in 1970, CO2 levels were measured to be approximately 320 parts per million, having increased steadily from slightly more than 314 ppm in 1960. Today, global mean CO2 concentrations have been measured to be approximately 390ppm. Again, when published, there was no “debate” as to the source of the increasing levels of CO2:
“The worldwide combustion of fossil fuels, principally coal and oil, on a prodigious scale in the modern era has materially increased the carbon dioxide level of the atmosphere. From measurements such as those graphed (from the cited study) it is clear that the CO2 concentration in the atmosphere is steadily increasing. From a knowledge of the infrared-absorbing characteristics of CO2 and water, and using a theoretical model for the atmosphere, it has been estimated that if the CO2 level were to double from its present level, the average surface temperature of the planet would increase 2.3 degrees Celcius. On the basis of present and expected future rates of fossil-fuel use, about 70 percent of the present known reserves of coal and essentially all the oil will have been consumed by about 2050. This amount of fuel consumption should just about double the atmospheric CO2 level. If the calculated effect of a doubling of CO2 level on surface temperature is correct, this means that the earth’s temperature will be 2.3 degrees C higher within 75 years. Such a small change may seem insignificant, but it is not. Major changes in global climate could result from a temperature change of this or even smaller magnitude. Because so many factors go into determining climate, it is not possible to predict with certainty precisely what changes will occur. It is clear, however, that humanity has acquired the potential, by changing the CO2 concentration in the atmosphere, for substantially altering the climate of the planet.”
The closing two sentences of the paragraph and the chapter on the chemistry of the atmosphere sound an ominous warning:
Unfortunately, if it should turn out for the worst, as seems altogether likely, there is little or nothing we can presently visualize that could be done about it. The continued high rate of combustion of fossil fuels is therefore a matter for long-range concern.”
With wind turbine technological advances and hybrid electric vehicles, and the recent advances in thin-film solar panels, we have come pretty far in our ability to reduce fossil fuel consumption if these were propagated more aggressively and became more ubiquitous, becoming the rule rather than the exception. But before delving into strategies to reduce carbon dioxide emissions, it is important to understand what we know about “the infrared-absorbing characteristics of CO2…”
Every material on earth absorbs electromagnetic energy, some frequencies of the electromagnetic spectrum better than others. The spacing between atoms in a material or molecule and the overall density determine which frequencies pass through, are absorbed, or reflected. This is classically illustrated in the use of X-rays. The higher frequency wave (than visible light) passes through flesh, is reflected by denser bone, and is absorbed by the extremely dense metal lead, which is used to protect health care professionals who would otherwise be constantly exposed.
Microwave radiation passes through plastics and ceramics, but is absorbed by water molecules. Actually, microwaves are such a match for water molecules that they force the water molecules to rotate back and forth with the changing electric field of the wave, and the friction between oscillating water molecules imparts heat to all surrounding matter… our food.
Carbon dioxide absorbs two distinct frequencies of infrared radiation. A simple way to think of this is that CO2 absorbs two “colors” within the range of frequencies known as “infrared” extremely efficiently. Remember we only see colors that are not absorbed by the materials we look at, that are reflected. When we see a white surface, all frequencies of the visible light spectrum are being reflected, and when we see black, no frequencies of the spectrum are being reflected. All colors in between imply the visible spectrum is being absorbed except for the color we see. (Of course, perfect reflection of all frequencies is only accomplished by a mirror, a material with enough surface electrons to instantaneously oscillate at the exact frequencies hitting it, re-radiating them in all directions.) Stealth technology employs materials and shapes that completely absorb radar frequencies, rendering aircraft and ships covered with them virtually invisible to radar equipment.
This all implies all light energy striking earth’s surface is absorbed. As the energy is absorbed, it increases molecular activity, increasing the effects of molecular friction, which generates heat, or infrared radiation. This is emitted in all directions, into the surface and back toward space. When atmospheric CO2 absorbs these two frequencies of infrared, the atoms of the molecule, one carbon and two oxygen, oscillate as if orbs on springs, and they oscillate at the frequencies they absorb. They re-radiate the absorbed energy in all directions, essentially reflecting much of it back toward earth. This is a good thing. As mentioned previously, this provides stability in temperatures between day and night.
How do we know CO2 absorbs two frequencies of infrared radiation? Infrared Spectroscopy.
Spectroscopy is the study of the interaction of electromagnetic radiation with matter. From an overview on infrared spectroscopy at ttp://www.wag.caltech.edu/home/jang/genchem/infrared.htm, which was adapted from “Modern Methods of Chemical Analysis” (R. L. Pecsok, L. D. Shields, 1968); and “Chemistry in Context” (A.T. Schwartz et al. American Chemical Society, Washington, DC 1994):
An infrared spectrometer consists of a glowing filament that generates infrared radiation (heat), which is passed through the sample to be studied. A detector measures the amount of radiation at various wavelengths that is transmitted by the sample. This information is recorded on a chart, where the percent of the incident light that is transmitted through the sample (% transmission) is plotted against wavelength in microns (um) or the frequency.
Figure 6 shows the infrared spectrum of a gaseous sample of carbon dioxide. Note that the intensity of the transmitted light is close to 100% everywhere except where the sample absorbs: at 2349 (4.26 um) and at 667 (15.00 um).
So we know CO2 completely absorbs 4.26 micron and 15 micron wavelength infrared radiation. It has helped maintain life as we know it on the earth. What is the impact of more CO2 in the atmosphere? More infrared radiation from the earth is reflected back toward the earth.
In other words, more heat is trapped by the atmosphere. Another way of looking at things, is that CO2 is a heavier molecule than oxygen and nitrogen. Therefore, there is more thermal mass, and the atmosphere has a higher “heat capacity.” Heat capacity is the amount of heat something can store, and is dependent on the object’s mass. Less overnight cooling due to more infrared reflected back toward earth by the more numerous CO2 molecules leads to higher daily average temperatures. These increases in one geographic spot would be imperceptibly small, but the net effect would be slightly higher global annual average temperatures.
The problem, then, is the upward trend of CO2 concentration. I’ve read a contrarian theory that suggests that the atmospheric CO2 is already absorbing 100% of the 4.26 and 15.00 micron infrared radiation emitted by earth. Therefore, more CO2 wouldn’t have any impact, since all the earth’s emitted infrared radiation is already reflected back toward it. More CO2 would just imply, according to this theory, that a lower percentage of atmospherically suspended CO2 molecules would be doing what the existing ones do at the lower percentage.
The fundamental flaw in this argument is that it assumes the only infrared radiation at play is that radiating from the surface. Readily available graphs and charts from NASA and other sources show that the atmospheric water vapor and CO2 absorb the frequencies coming from the sun we would now expect them to. This implies more CO2 in the atmosphere would be capable of absorbing more heat coming directly from the sun… as expected.
Another flaw by omission is the impact of the albedo effect. If the planet loses its polar ice, the amount of energy the darker oceans would absorb would increase dramatically compared to when frozen and white. This would increase the amount of infrared radiation given off by earth’s surface, only to be absorbed by more abundant CO2 and reflected back toward earth as diffuse radiation. It seems redundant to say this would lead to ever-increasing temperatures.
Another article I read placed huge emphasis on one NASA insider’s opinion that Hansen, one of the people in the public eye bringing awareness to the phenomenon of global warming, didn’t account for clouds correctly in his analysis of the data. No peer reviewed study, data or conclusions or numbers were provided, only an opinion that Hansen was wrong, an alarmist, or whatever, because he did not include clouds in his projections of temperature increases. Water vapor, while being a principle component of the “green house effect” is not a “forcing” component. Its lifetime in air is a matter of days, while CO2 lasts for years. There is probably a whole post’s worth of material discussing forcing functions and feedback functions…
Others cite satellite data collected since 1979 that showed a cooling trend. In August of 2005, an anomaly in satellite time-of-day settings was corrected. The satellites had been measuring evening and night time temperatures instead of daytime temperatures, skewing results lower. Once corrected, the satellite data supported all working model projections.
Others cite a cooling trend from 1998 to present. 1998 was the warmest year on record. Using that as a starting point for a trend can only lead to a conclusion the global average temperatures are decreasing. It is a deceptive tactic to prejudice trends observed for many years.
In my next post I’ll cover some data that gives an idea of what the authors of my 32 year old text meant by “…combustion of fossil fuels, principally coal and oil, on a prodigious scale…” On this topic, a parting reminder:
One gallon of gasoline weights approximately 6.5 pounds. When burned, one gallon produces approximately 19.5 pounds of CO2. Remember the process of burning means combining with oxygen, or oxidizing. Diesel produces 22 pounds CO2 per gallon. The greatest contributor of CO2 to the environment, however, is coal, because the volumes burned to produce electricity. One pound of coal produces approximately 3.7 pounds of CO2 when burned. The volumes we emit from transportation and electricity production in this country alone are stunning.
Since we seem to be on an irreversible trend toward higher and higher concentrations of atmospheric CO2, one of the next logical steps for science is to ask the question: “what will the planet’s surface look like?” and “has it ever been like this before?” “With no polar ice, will ocean currents collapse?” “What effect will extreme atmospheric changes (like much weaker ocean currents due to lack of polar ice) have on all the planet’s farmland?” “What if mountain snow melt no longer exists after May, if it all melts by the end of March?”
This is where controversy really sets in, because best guesses can be downright frightening to people who really would like “this year to be much like last year.” If the ocean rises 3 feet, what would happen to our economy, our way of life, the planet’s economy, if San Diego, CA, most of Florida, and Manhattan became uninhabitable, not to mention Bahrain and Saudi Arabia? How many million people would have to move inland? How will my kids eat? This is when people freak out. Just as much as the next guy, I’d prefer to be able to kick back and go to a fantasy football draft party. Instead, I get wrapped up in projects to do my part to reduce my contribution to the consumption of fossil fuels. This post is one part. So, in conclusion, the chemical and electromagnetic phenomena associated with what is now known as “global warming” and “the climate crisis” have been under observation by scientists for well over 30 years. And yes, as George Carlin is famous for saying, the planet will be fine. However, the planet’s ability to support life as we have come to know it seems to be at risk. Since I live on it with my kids, and eventually, my grandkids, I care.