Faithful reader Florence Algar has been asking the Fib Finder to comment on the issue of global warming for the last year. After having just finished shoveling out from under 24 inches of global warming in the last week, it seemed about the right time to sit down with aching back and ponder the topic.
The Earth is blanketed in an atmosphere of gases which allows us to breathe, fly kites, and enjoy blue skies. Perhaps most importantly, the atmosphere acts as a greenhouse. Heat from the sun would quickly radiate away from the Earth each night without the atmosphere. The result would be toasty warm days, but bitterly cold nights.
Such a situation exists on Mercury. As the closest planet to the sun, days on Mercury are quite hot--high enough to melt lead. However, with no atmosphere to retain the heat, nights on Mercury are very cold--perhaps as low as -250 F.
Venus, on the other hand, has a dense atmosphere which is composed largely of gases which retain much of the sun's energy. Though Venus is farther from the sun than Mercury, the days are even hotter. Importantly, nights on Venus are nearly as hot as the days. Venus is a situation which we would call a runaway greenhouse.
The global warming crowd is not concerned with Earth being a greenhouse. It is a greenhouse, and must be so to remain hospitable. The concern is the Earth will become a runaway greenhouse like Venus.
Our atmosphere contains nearly 80% nitrogen, about 20% oxygen, less than 1% carbon dioxide and traces of several others. While this mixture remains constant over long periods of time, dynamic changes occur constantly. Microbes fix nitrogen and remove it from the air. Organisms that respire (all plants and animals) consume oxygen and add carbon dioxide. Photosynthesis (all plants) adds oxygen. Anaerobic degradation of biomatter generates methane (such as the digestive systems of cattle and compost piles). Combustion (forest fires and fuel consumption) adds carbon dioxide.
Different gases have different abilities to retain heat from the sun. Carbon dioxide and methane, for instance, retain heat better than nitrogen and oxygen. The "global warning" is that our huge consumption of fuels is adding sufficient carbon dioxide to the air that the greenhouse will retain more heat and bad things will happen.
That is a simple statement of the theory, which was first stated a century ago. (1) Proving the theory is ,however, another matter (unless you are Al Gore and believe that a "controlling legal authority" can decide all earthly issues).
The fact is that the Earth is quite large and many factors contribute to heat retention. No one has yet devised a model that we can all agree upon. We haven't kept records nearly long enough to detect any real trends. We probably don't have sufficient computing power to do the job, and we certainly don't have the apparatus in place to collect the data that would have to be entered into the model.
Attempts have been made, to be sure. But each valiant attempt, each conflicting result, serves mostly to illustrate the complexity of the situation and the feebleness of our efforts to describe it.
We only started monitoring carbon dioxide concentrations in the air in 1958. (2) We have only monitored temperatures for about 100 years. And while there have been clear increases in both in that time, we don't understand the reasons why. It may well be an entirely natural cycle.
Until about 1975, the carbon dioxide concentration increase tracked increases in fuel burning. But in the last 15 years, carbon dioxide levels have surged ahead of fuel burning and then lagged behind. This suggests natural factors at work. Warmer land increases the growth of vegetation, which removes carbon dioxide; warmer ocean water expels the gas as its solubility decreases, etc. (2)
It has been suggested that increased vegetation would increase the greenhouse effect. At higher carbon dioxide levels, plants release less water, increasing the temperature near the plants, and ultimately increasing the temperature of the earth. (3)
On the other hand, attempts to calculate the total carbon in the cycle by comparing carbon dioxide emissions against the known mechanisms for its removal from the air suggest that 1.8 gigatons/year of carbon dioxide "disappear." (4) In other words, we don't know all the mechanisms that control carbon dioxide levels.
Published papers have concluded that greenhouse gases are increasing the temperature of the troposphere and stratosphere. (5) However, another study finds that clouds reflect more heat back into space than had been predicted. (6)
It is argued that temperatures, both day and night, are increasing, and will continue to do so for the next couple hundred years. This is considered to be consistent with "the model" for the greenhouse effect. (7) But, loblolly pines were found to trap huge quantities of carbon dioxide below the ground where it may be stable for thousands of years. (8)
And while there has been an increase in the total number of hot, humid days--results generally consistent with an enhanced greenhouse, (9) "the model" also predicts increased precipitation and flooding--which has not materialized in the last 50 years. (10)
The most gloomy greenhouse predictions have relied on a doubling of methane concentration by the year 2100, but methane concentrations have been increasing at a slower than predicted rate and may soon begin to abate. (11)
The tree huggers implore us to plant more forests, but it would prove to be a temporary decline in carbon dioxide at best. At the trees died, they would mostly compost back to carbon dioxide. (12) Right now, decay of forest debris returns 85 billion tons of carbon dioxide to the atmosphere annually. (13)
Satellite data has always suggested the Earth is cooling at 0.1 F/decade while surface measurements suggest a warming of 0.2 F/decade. New findings correct for orbital variations of the satellites and now report warming of 0.15 F/decade. But wait, there's more. The guy that invented the satellite technique has now applied yet another correction factor and reports overall cooling again. (14)
So, what are we supposed to do? Who do we believe?
I say, do whatever you want. It won't make any difference. Logging practices have changed dramatically in the last quarter century. Today, there is more forested acreage in the US than 100 years ago. We have twice as many cars on the road now as 30 years ago, but we only use 10% more gasoline. The entire history of the industrial revolution has been one of continued improvement in efficiency of energy use and pollution abatement. The problem, if it exists, is going to be solved before it is proved.
I have to go. Another 4 inches of global warming just fell and needs to be shoveled. We are now only 2 inches away from the snowiest January on record--which was 1978. But wait......I have heard it said that all this snow is actually predicted by the global warming model.........
1. D. A. H. Taylor, Chemical and Engineering News, (May 6, 1996) p. 60.
2. R. Monastersky, Science News 147.
3. P. J. Sellers, T. G. Jensen, et. al., Science, 271 (1996) p. 1402.
4. K. L. Griffin, J. R. Seeman, Chemistry and Biology, 3 (1996) pp. 245-54.
5. S. F. B. Tett, et. al., Science, 274 (1996) p. 1170.
6. R. D. Cess, et. al., Science, 267 (1995) p. 496; V. Ramanathan, et. al., Science, 267 (1995) p. 499; Chemical and Engineering News, (February 6, 1995) p. 23; B. Hileman, Chemical and Engineering News, (February 13, 1995) p. 33.
7. B. Hileman, Chemical and Engineering News, (November 27, 1995) pp. 18-23.
8. Science News, 150 (September 21, 1996) p. 186.
9. D. J. Gaffon, R. J. Ross, Nature, (December 10, 1998); Science News, 155 (January 16, 1999) p. 47.
10. H. F. Lins, J. R. Slack, Geophysical Research Letters, (January 15, 1999); Science News, 155 (January 16, 1999) p. 47.
11. D. Schneider, Scientific American, 278 (June, 1998) p. 14.
12. H. C. McKee, Chemical and Engineering News, (March 23, 1998) p. 4.
13. Omni, 17 (February, 1995) p. 33.
14. B. Hileman, Chemical and Engineering News, (August 17, 1998) p. 7-8.
