by Gunter Chang

Created on: January 23, 2009

The term and theory of "nuclear winter" was popularized in 1983 by Carl Sagan and associates stemming from a scientific paper, "Global Atmospheric Consequences of Nuclear War".Written by R. P. Turco, 0. B. Toon, T. P. Ackerman, J. B. Pollack and Carl Sagan, this work is also referred to as "TTAPS" from the initials of the authors' last names. The premise was that nuclear war would create a global environmental catastrophe, regardless of where it occurred, resulting in the earth being plunged into a "nuclear winter". While, nuclear winter describes the climatic effects stemming from a nuclear war, it has also been used to describe the aftermath of asteroid impacts and super-volcano eruptions since the mechanisms are similar.

In theory, vast amounts of dust kicked up into the upper atmosphere from impact, and smoke from burning cities would obscure the sun for days, if not weeks after a nuclear war. This effectively cools the climate and damages the ecosystem during a prolonged state of winter-like conditions. The trail of destruction eventually encompasses millions who may not have even been involved in the nuclear exchange yet still succumb to mass starvation brought on by the ensuing crop failures. At the time of the study, there were only 50,000 nuclear weapons, yielding more than 13,000 megatons of destructive power. Twenty-six years later, the world has seen the emergence of new super-powers and their arsenals, as well as increasing capacity in the pre-existing arsenals.

Cooling from smoke and dust isn't the only mechanism at work here. It was discovered in the 1970's that high-yield airbursts chemically burn nitrogen and convert it into nitrogen oxides; these then combine with ozone in the upper atmosphere, destroying the protective ozone in the Earth's stratosphere. Without the ozone shield, deadly solar ultraviolet radiation would take a toll on the biology of the planet. But, where in this "micro-waved popcorn" nightmare scenario does the nuclear winter prospect come in? The other piece of the puzzle came in 1971, when Mariner 9 arrived at Mars in the midst of a global dust storm. Taking temperature readings over the next months, scientists noticed as the fine dust settled, the Martian surface heated up.

Sagan's study postulated an explosion of 5,000 to 10,000 megatons in a nuclear conflict and calculated the devastating climatic effects. Sagan and associates knew that nuclear explosions, especially ground-bursts, would throw tremendous quantities of soil

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