CO2 and Global Warming
Jim Blair

This post is largely in response to recent articles about global warming that have appeared in The Economist, April 1-7 (Global Warming and Cooling Enthusiasm p33, and Reading the Patterns p65) and in National Review, May 1 (Hot Air in Berlin p18). These articles were topical because of the United Nations Climate Conference in Berlin last month.

The first Economist article is mostly about the international politics of the debate: OPEC nations strongly oppose any action to reduce emissions since "greenhouse gases" means mostly CO2 which comes from burning petroleum. Low islands and countries with low sea coast regions are more interested in doing something. Poor countries don't want their energy options limited before the can industrialize--unless they are compensated. The rich energy efficient nations of Europe made promises to reduce emissions, but now, faced with keeping them, are losing enthusiasm.

But my concern here is with the science: Will current practice alter the climate of the earth?

What gas?

Every object emits energy depending on its temperature:("black body" radiation). The hotter the object the shorter the wavelength. For very hot objects the radiation can be seen, as in "red hot", or if even hotter, "white hot". For cooler objects, you can't see the energy, but it is still there as infrared (IR) which you may feel as heat, or microwave which you can't feel. A sidewinder snake can find a mouse in the dark by detecting the heat the mouse emits. The earth emits in the long IR. Even the black empty space of the universe emits 7.35 cm radio energy, corresponding to 3 degrees K, heat left over from the Big Bang.

Polyatomic gas molecules absorb long IR and microwave energy when they tumble. CO2, with 3 atoms per molecule does this. So does methane (CH4) and water vapor (H2O). These gases in the air adsorb IR energy that the earth would otherwise radiate into space. They act like a blanket.

"Greenhouse gases do not "absorb" heat. They make the atmosphere less transparent to the infrared."

I think it perfectly acceptable to say that CO2 "absorbs heat". Infrared radiation that would otherwise pass through an atmosphere goes in one side (here the bottom) and does not come out the top. It has been "absorbed". The energy of the IR is transferred to the CO2 molecules causing them to tumble faster, and this transfers some of the energy formerly in the IR radiation to the other gases in the atmosphere by the collisions. They then move faster. This is commonly called being "warmer".

If anyone thinks that the transfer of IR energy (commonly called "heat") into the earth's atmosphere will not result in any change, they should offer some explanation as to just what they think happens to that extra energy. And besides more energy there is also a change in the energy distribution of the atmosphere. More heat absorbed in the lower atmosphere would mean less made it to the upper atmosphere: the lower would be warmer, but the upper would be cooler. So to measure this effect, it is important just which part of the atmosphere is examined.

Who, us?

Human activity releases CO2 from the fossil fuels that we burn, especially since the industrial revolution. The CO2 level in the air has been monitored since the 1950's and is increasing. Besides a natural annual change (it drops each spring as plants grow and rises each fall as leaves decay), there has been a steady background rise of about 20% in the past 100 years. This is caused by humans. And it should cause the earth to get warmer.

Nearly 100 years ago the Swedish chemist Svante Arrhenius and the American geologist Thomas C. Chamberlin independently advanced the hypothesis that changes in the abundance of carbon dioxide in the atmosphere would affect the surface temperature of the earth. Arrhenius estimated that a doubling of the concentration would cause a global warming of about nine degrees C. In 1939 G. S. Callendar suggested that the global warming observed over the previous 60 years might have been caused by an increase in atmospheric carbon dioxide from the burning of fossil fuels. Gilbert N. Plass argued along similar lines in the early 1950's.

None of the above is in dispute. But when coal burns it also releases small particles and SO2 which forms small droplets: these reflect incoming sunlight and cool the earth. This offsets the warming effect, but the relative balance is in dispute. Also there is a "law of diminishing returns" here. Maybe CO2 levels are already high enough that more does not make much more difference.

The real issue: compared to what?

The other two articles cited both view the problem as a "signal-to-noise ratio" problem, and so do most who discuss it. Is the earth actually warming? Can the warming "signal" be measured against the natural variations in temperature "noise level"? But they misunderstand the nature of the problem: it is actually a "compared-to-what" problem. What is the basis of the comparison? That is, is the earth warmer than what?

Humans have been raising the CO2 level for several hundred years. The earth was warning up as expected until about 1940, but has not warmed up as much as predicted since then. The implied comparison is to a "flat" baseline of constant temperature. There is no "control earth" without a build up of CO2 to compare to. But the proper comparison is to the expected temperature.

I am surprised no one else seems to understand this because I thought it was common knowledge that history has been characterized by warm and cold cycles of 50 to 100 year duration, for example, ice skating and winter fairs on the Thames river in London during the "little ice age" of the 17th century.

Where did the little ice age go? Global warming ate it!

Studies of the ice cores drilled in the Greenland glacier suggest a pattern of cold spells based on the superposition of two cycles: 80 years and 180 years. The causes of this complex pattern is not known (but there is some C-14 evidence that the 180 cycle may be due to changes in the sun). At any rate this pattern fits all the cold spells since 1200 A.D.--except that we should now be in a cold period that should have started about 1950 and continue until about 2000 A.D. These results were published in the 1970's.

The cycles are associated with Willy Dansgaard, and are discussed in the chapter on the history of climate in the text book GEOLOGY TODAY from CRM. See Figure 1 for the past record of warm and cold spells since 1200 AD, and the predicted "little Ice Age of 1970-2000 AD.

At about the same time, the proponents of the greenhouse effect were predicting a global warming, but they did not consider the natural climate cycle.

Since neither the predicted warming nor the predicted cold spell has happened, the conventual wisdom is that both ideas are wrong. I think it is at least as likely that both are correct: but since 1950 the two have been canceling each other out. Just when the natural cool period was beginning to weaken, the eruption of Mt. Pinatubo produced a few years of extended cooling. Now that effect is wearing off, and the natural cold cycle will give way to a warm cycle which will add to the greenhouse warming rather than subtract from it. Things should warm up in the next decade. See Figure 2 for how the expected cold spell is greatly reduced by the effect of the CO2 increase.

The twisted politics of energy - nuclear power

There is a strange political component to what should be a technical- scientific question. The Left believes in the green-house effect and the Right doubts it. But the Left opposes nuclear power while the Right supports it. When the dangers of CO2 are understood, the greenhouse effect is a compelling argument for shutting down coal and gas power plants, and only nuclear ones can replace them - at least in the short run.

Solar or wind is not yet capable of replacing the coal plants. Steam turbine natural gas (ie methane) has been proposed as an alternative, but although methane releases less CO2 per kilowatt of electricity generated, it still burns to CO2. And the more it is used, the more will leak or spill into the atmosphere, where it is much more effective as a greenhouse gas than CO2.

Until the collapse of the Soviet Union, the three major objections to the use of nuclear reactors to generate electric power were the mining of uranium, the safety of the reactor operation, and the disposal of the reactor waste products. No one seems to realize that it is a different world today.

The former Soviet Republics have about 28,000 nuclear warheads, and the US about as many. They contain enough uranium and plutonium to supply the worlds electricity, probably until solar or fusion becomes practical. Whatever the risk of a state-of-the-art nuclear power plant, it is certainly safer than a nuclear warhead. And reactor waste presents less of a disposal problem than weapons grade uranium or plutonium. See 'GREENHOUSE GAS & THE ECONOMY' (on my web site) for my plan to deal with these problems.

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