The Nuclear Winter by Carl Sagan Read Free Book Online Page B

[The scientific paper, "Global Atmospheric Consequences of Nuclear War," was written by R. P. Turco, 0.
    B. Toon, T. P. Ackerman, J. B. Pollack and Carl Sagan. From the last names
    of the authors, this work is generally referred to as "TTAPS."]
    We knew that nuclear explosions, particularly groundbursts, would lift an
    enormous quantity of fine soil particles into the atmosphere (more than 100,000 tons of fine dust for every megaton exploded in a surface burst).
    Our work was further spurred by Paul Crutzen of the Max Planck Institute
    for Chemistry in Mainz, West Germany, and by John Birks of the University
    of Colorado, who pointed out that huge quantities of smoke would be generated in the burning of cities and forests following a nuclear war.
    Croundburst -- at hardened missile silos, for example -- generate fine dust. Airbursts -- over cities and unhardened military installations --
    make fires and therefore smoke. The amount of dust and soot generated depends on the conduct of the war, the yields of the weapons employed and
    the ratio of groundbursts to airbursts. So we ran computer models for several dozen different nuclear war scenarios. Our baseline case, as in many other studies, was a 5000-megaton war with only a modest fraction of
    the yield (20 percent) expended on urban or industrial targets. Our job,
    for each case, was to follow the dust and smoke generated, see how much sunlight was absorbed and by how much the temperatures changed, figure out
    how the particles spread in longitude and latitude, and calculate how long
    before it all fell out in the air back onto the surface. Since the radioactivity would be attached to these same fine particles, our calculations also revealed the extent and timing of the subsequent radioactive fallout.
    Some of what I am about to describe is horrifying. I know, because it horrifies me. There is a tendency -- psychiatrists call it "denial" --
    to
    put it out of our minds, not to think about it. But if we are to deal intelligently, wisely, with the nuclear arms race, then we must steel ourselves to contemplate the horrors of nuclear war.
    The results of our calculations astonished us. In the baseline case, the
    amount of sunlight at the ground was reduced to a few percent of normal-much darker, in daylight, than in a heavy overcast and too dark for
    plants to make a living from photosynthesis. At least in the Northern Hemisphere, where the great preponderance of strategic targets lies, an unbroken and deadly gloom would persist for weeks.
    Even more unexpected were the temperatures calculated. In the baseline case, land temperatures, except for narrow strips of coastline, dropped to
    minus 250 Celsius (minus 13 degrees Fahrenheit) and stayed below freezing
    for months -- even for a summer war. (Because the atmospheric structure becomes much more stable as the upper atmosphere is heated and the low air
    is cooled, we may have severely underestimated how long the cold and the
    dark would last.) The oceans, a significant heat reservoir, would not freeze, however, and a major ice age would probably not be triggered.
    But
    because the temperatures would drop so catastrophically, virtually all crops and farm animals, at least in the Northern Hemisphere, would be destroyed, as would most varieties of uncultivated or domesticated food supplies. Most of the human survivors would starve.
    In addition, the amount of radioactive fallout is much more than expected.
    Many previous calculations simply ignored the intermediate time-scale fallout. That is, calculations were made for the prompt fallout -- the plumes of radioactive debris blown downwind from each target-and for the
    long-term fallout, the fine radioactive particles lofted into the stratosphere that would descend about a year later, after most of the radioactivity had decayed. However, the radioactivity carried into the upper atmosphere (but not as high as the stratosphere) seems to have been
    largely forgotten. We found for the