Tuesday, October 26, 2004

Politics and Atmospheric Physics

The recent approval of the Kyoto Treaty by the Russian Duma presages its eventual passage and signature by Vladimir Putin. Once Russia approves the treaty it will take effect for all signatory nations. John Kerry will be pleased with the UN effort. The only major first world economies to not sign the treaty are the United States and Australia. We can be sure the UN, Old Europe and the enviros will start wailing. So a little review of the history of the confluence of politics and atmospheric physics is in order.

The first big push was made in 1983-84 under the banner of “Nuclear Winter”. It was an adjunct to the Nuclear Freeze movement. John Kerry was lieutenant governor to its prime adherent, Democratic presidential candidate Michael Dukakis. The leading public scientific face was Carl Sagan. He was one of the authors (TTAPS - Turco, Toon, Ackerman, Pollack & Sagan) of the leading study initially published in the magazine, Scientific American.
The synopsis of the theory was that a nuclear exchange targeted on cities would cause extensive fires. Soot and dust rising from them would rise into the stratosphere where it would block out the sun. This would cause global cooling and plunge the world into a period of greatly reduced temperature that would last a long time as the soot would be above the natural cleansing effect of rain in the troposphere.

No one was inclined to defend the concept of all out nuclear war, so it was hard to hear the skepticism that existed. But a cursory review of the physics would show enormous uncertainties in the theory. The average citizen would likely be sufficiently credulous to believe the scenario. If the sky was darkened, they might expect it to be cooler based on their experience with the sun hiding behind a cloud. It’s “cooler in the shade” seems to support the notion. But what about at night? Aren’t the coldest times of day just before dawn on a really clear night? Ooops! We might wish to consider diurnal variation in our theory. But TTAPS used a time averaged model that simulated a continuous twilight. And the model was a one-dimensional radiation-convection model in a three dimensional universe!

Obviously, the model was weak. One way of approaching a problem beyond your computational capabilities is to devise a simplified model. Let’s try one. Imagine an Earth sized planet surrounded by a cloud bank that reduced solar radiation at the surface to 1-2% of the average radiation seen at Earth’s equator. What would you think would happen to the surface temperature? Would it drop 25-50 degrees as predicted by TTAPS? No!. Because I’ve just described the planet Venus where surface temperatures are hot enough to melt lead. So the plausibility to the credulous public does not signify scientific truth. But the awfulness of the post-war effects of a nuclear war were enough to stampede the populations of Europe! It meshed with the Soviet disinformation campaign to prevent the installation of Pershing missiles in Europe. It was a political force, if not a scientific one. I’ll probably do more posts on the subject of “nuclear winter”, but I think you can start to see the emperor’s new clothes.


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