The Greenhouse Effect

Meteorologist Craig James, new Squire columnist

In last week’s article I gave you the basic overview of what I think the science really says about human induced global warming. Let’s start this article by taking a look at the poorly named greenhouse effect.

I think there are several things about our atmosphere most people are not aware of. The first is that the energy from the sun, short wave radiation, does not heat up the air. About half of the solar radiation is reflected back into space from clouds, water, ice, etc while the other half is absorbed by the ground. As the ground absorbs the short wave radiation, it heats up and emits what is called long wave radiation back into the atmosphere and this long wave radiation is what heats the air.

Some of this long wave radiation passes through the atmosphere back out into space but most is absorbed by greenhouse gas molecules and clouds, then re-emitted in all directions. Much of the re-emitted radiation goes back to earth while other greenhouse gas molecules and clouds absorb some of this energy only to re-emit it again. The effect of all of this is to warm the air. Without our atmosphere, the earth would average about 50 degrees colder than it is now.

However, at no time does the atmosphere act like a blanket or a greenhouse and trap heat. When someone says CO2 traps heat in the atmosphere they don’t understand what is actually occurring. Nothing is trapped. The energy courses through the system without being trapped within it and this process, poorly labeled the greenhouse effect, is absolutely necessary for life as we know it.

If the amount of energy leaving the top of the atmosphere equals the amount of energy being added to the atmosphere from the sun and the greenhouse gases, the earth’s average temperature will remain unchanged. Many natural processes such as a change in the amount of cloud cover or volcanic eruptions disturb this balance and the earth is always cooling or warming slightly at any time.

It seems to be rather intuitive then that if you add more greenhouse gases to the atmosphere, you will increase the temperature of the atmosphere. The question is, how much? There are currently 390 molecules of CO2 per one million molecules of atmosphere. That represents just 0.039%, or just a trace amount. By far and away, the most prevalent and effective greenhouse gas is water vapor. As you can see from this pie chart, water vapor contributes about 95% to the greenhouse effect and CO2 from human activity contributes about 0.28%.





We do know for certain that the amount of CO2 in the atmosphere is increasing, but how much of a direct effect does an increase in CO2 produce? Let’s pretend we have an atmosphere with no CO2. As you can see from the following graph, the first 20 parts of CO2 we add to the atmosphere have a much greater impact on the temperature than the next 20 parts and the next 20 parts, etc.

There is only a small effect on the temperature as we increase the CO2 from 280 parts per million, the pre-industrial level, to the current level. Doubling the CO2 concentration from here would have very little direct effect at all. Adding CO2 to the atmosphere has what is called a logarithmic effect, not a linear one. The more CO2 you add, the less impact there is upon the temperature. What is amazing is even the people who believe in catastrophic global warming agree that this is so.

So how do we get to catastrophic warming by adding more carbon dioxide to the atmosphere? Ah…it is from those wonderful computer models. The models that are tuned to bad data, incorporate false assumptions about the atmosphere, and have proven to be wrong where we can test them. I’ll show you this in future articles.

Craig James has been retired since July 1, 2008, after 40 years of broadcasting television weather. He was chief meteorologist at WZZM-TV for 12 years and chief meteorologist at WOOD-TV for 24 years. He is a graduate of Penn State University, where he received a Centennial Fellowship Award. He was also honored as a Fellow of the American Meteorological Society.



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