Before there was Global Warming Theory to scare the public into rash action, there was Nuclear Winter Theory. The two theories are contradictory, but both were peddled by the political left, and both used some similar rhetorical and political tactics.

This year is the 25th  anniversary of Carl Sagan's Cosmos series on public television, a landmark in the public's awareness and interest in science issues. Sagan achieved a degree of celebrity  few if any scientists today enjoy, particularly among the bon pensants who tend to treat anything produced by PBS as holy writ.  It is a fitting time to look back at the genesis of today's climate debates, for Sagan became one of the first politicizers of fear of catastrophic climate change.

By 1983, Sagan and others had formed a group known as TTAPS (Turco, Toon, Ackerman, Pollack & Sagan). They proposed that a consequence of nuclear war would be a major cooling of the Earth's atmosphere, an effect they called 'Nuclear Winter.'  This was the first great politicized debate over climate.

Sagan even appeared with Walter Mondale on the campaign trail in 1984 to promote the Nuclear Freeze Movement as an alternative to Ronald Reagan's 'Star Wars' missile defense initiatives. Reagan was building up our armed forces and positioning Pershing missiles in Europe. History has proven Reagan's policies superior to Sagan/Mondale. So could it also be that Sagan & TTAPS need re—evaluation from a historical point of view? Let us make an attempt at a few aspects of a very complex issue. 

Public Credulity

Given that the issue of climate is extremely complex, the public and the politicians are inclined to rely on 'expert opinion.'  Simply put, they do not have the knowledge base to make a coherent criticism of something this technical.

Science relies on getting a new idea published in refereed journals and then letting skeptics blast away at the hypothesis.  TTAPS instead  relied on a public relations effort, a 'Conference on the Long—Term Worldwide Biological Consequences of  Nuclear War' (1983 : Washington, DC). The conference transcript forms a part of Sagan's book,  The Cold and the Dark, the World after Nuclear War, published by W. W. Norton & Company,  New York, N.Y., a work which will be quoted extensively herein.

Despite the complexity of the issue, anyone is entitled to challenge the assumptions and/or fallacies within. This need for open—minded questioning is why we re—tell our children the story of The Emperor's New Clothes. So here are some questions and comments the interested novice might have posed to that august collection of luminaries who first used fear of climate change as a political weapon.

Appeals to Authority

TTAPS (and nowadays the global warming crowd) liked to make statements to the effect that 'most credible scientists agree....' Yet the scientific conventional wisdom can be wrong. What do you think the global warming crowd would say to the following Sagan statement?

Let me stress that the CO2 greenhouse effect is a long—term trend. There is no undoing it on time scales of decades.  (pg. 31)

Not exactly a hearty endorsement of the Kyoto Treaty is it?  But Carl Sagan was a media star, the most famous scientist of the day. The point is that at that time Sagan was trying to peddle his 'Nuclear Winter' scenario and he could not allow the CO2 from the combustion of cities to mitigate the horror of the world freezing in the dark. He wanted the maximum panic by the public to push through his political agenda. He was more politician than scientist.

The Missing Products of Combustion

The principal culprit in the 'Nuclear Winter' scenario was soot in the smoke form burning cities. As we've just seen, TTAPS downplayed the CO2. The other major constituent of smoke is water vapor. Indeed, it is the condensing water which becomes visible to the naked eye, that most people would identify as 'smoke.' Sagan dismisses the effects of water and clouds,

...in our calculations we assumed that rainout of fine particles occurred through the entire troposphere. But under realistic circumstances, at least the upper troposphere may be very dry, and any dust or soot carried there initially may take much longer to rainout' (pg. 21).

Those following the global warming debate will find that the issue of clouds is still a very hot topic of debate. Note that by eliminating the two major products of combustion TTAPS can focus the discussion exclusively on soot.

Real World Analogies

For a hypothesis to advance toward acceptance, it needs to enhance our basic understanding of natural processes.  We ought to be able to draw new insight into old observations. So let us look at some unrelated situations and try to draw analogies.

Smudge Pots: the dense sooty smoke from burning cities has another name, smudge. Back in the days before the EPA, citrus growers used smudge pots to keep their groves from freezing during cold nights.  This was a proven, successful way to prevent freezes. So how does Sagan's smudge result in 'nuclear winter'? This question exposes a critical failing of the TTAPS scenario. They used a climate model based on a time—averaged solar input. Their model never sees a cycle of day followed by night,  just a constant dim sunlight.

If a cloud blocks the rays of the sun, we notice a cooling effect. But at night, clouds prevent the loss of infrared radiation to deep space and we feel warmer. The coldest nights are those where a snow cover under a clear sky reflects the day's sunlight out to space, followed by a clear night allowing unimpeded infrared radiation. The lower solar input combined with enhanced radiation leads to frigid nights.

Planetary Comparisons: the TTAPS modelers used Mars for the basis of much of their theorizing. But Mars'atmosphere is largely composed of CO2 and contains little water. There are only occasional cirrus ice clouds on Mars. So let us create our own simple planetary model with clouds. To keep it simple, let's start with a planet about the size of Earth. We'll enshroud it in a cloud layer covering the whole planet. We set the amount of solar energy at the surface at about 1—2% of that which normally reaches the surface of Earth. What does our model reveal? A pronounced cooling , a small +/— effect or pronounced heating? 

Made your choice? The answer is pronounced heating, because I've just described the planet, Venus. Its surface temperature is high enough to melt lead! So maybe clouds do matter after all.

A Three Dimensional World:  the TTAPS model was a one—dimensional radiation—convective model. The limitations of then current computational capabilities precluded using a three—dimensional model. To quote Sagan,

the detailed TTAPS calculations described here are one—dimensional; that is, they assume the fine particles to move vertically by all the appropriate laws of physics, but neglect the spreading in latitude and longitude.

There are many fine illusionists who delight the public by presenting a two—dimensional view to them, while acting in the third dimension.  A one—dimensional model is hopelessly inadequate,  but that did not restrain the boasts of Sagan et al.

Lessons

The key to looking at climate science is to remain humble, and admit that there is much that we do not know. Without that basic honest humility, the public should remain skeptical of all doomsday scenarios, but especially those which are being used for political gain.

It is also important to recognize that most climate scientists receive their funding either directly or indirectly through federal government grants (e.g. through NASA).  To increase funding it helps to have the political class anxious to use their findings as a political club. Climatologists are unusually vulnerable to the temptation to exaggerate to keep the money flowing.

Caveat Emptor.