In the 1980s, well known scientists such as Carl Sagan, initially using information provided by satellite image analyses of planet-wide Martian dust storms, concluded that a nuclear weapon exchange as small as 100 megatons (about what could be provided by one US nuclear missile submarine) would decimate the Earth with a "nuclear winter," dropping surface temperatures for several months by about 50° (to around -9°F if the conflict occurred in summer for the northern hemisphere). Though this effect would be temporary, normal mercury readings expected to be restored in from one to several years, it might be sufficient to kill off a large proportion of our kind, not to mention other animals and many of the world's plants.

This concept was popularized in the press, books, or movies, and by interest groups, not to mention by governments, such as the USSR, since it was in their interest to have people think a nuclear war was not survivable and hence no longer a viable option.

Although there are plenty of reasons not to have even a modest nuclear exchange (radiation poisoning spread around the globe, destruction of the upper atmosphere's ozone layer [making everything alive more vulnerable to ultraviolet rays], agricultural damage, economic devastation, city and population decimation from the nuclear blasts themselves, etc.), subsequent research has somewhat discredited the notion of a nuclear winter from a merely small-scale nuclear exchange. More recent estimates suggest that a "typical," modest nuclear war, involving maybe 50 times the nuclear force of the Hiroshima atomic bomb detonation, would only lower the world's temperatures in the range of 2 to 20°F, a far more manageable amount.

And since there is general agreement that such heat reductions would be of fairly short duration, a few months to about a decade at most, it seems now less likely that even a global thermonuclear war would permanently alter the climate, though it might result in the deaths of many, from altered climate conditions alone, before a proper balance would be restored.

On the other hand, the world's arsenal of nuclear weapons is absolutely huge, with tens of thousands of atomic or hydrogen bombs and missiles at our disposal, plenty for all the desired obliteration of any conceivable enemy, with still the equivalent of millions and millions of tons of TNT explosive energy left in reserve.

In fact, with up to a couple dozen or so additions to the nuclear club projected over the next 20 or 30 years, and a conflict that could well have led to the world's first nuclear exchange as recent as the late 1990s (between Pakistan and India), it does not stretch credulity to think that events may overrun speculation before too much longer. Then we may, willy-nilly, have our next big test of human ingenuity and weather manipulation, once nuclear missiles are soon being flung back and forth. We can then determine directly whether or not the results are sufficient to offset the global warming counter-trend.

But I suggest a more proactive approach. Why not harness all that energy like a world air-conditioning system, the "on" switch triggered by a satellite tracking "thermostat" that would show whenever, as is now the case, the globe is starting to heat up again?

Consider that when the biggest recorded volcanic explosion occurred, Tambora (1815), so much extra gas, dust, and soot were pumped into the atmosphere that they blotted out a significant portion of the sunlight that normally would have reached Earth, causing a "year without a summer," significantly dropping global temperatures for several months or years afterward. That spring was terribly cold, and snow still occurred in much of Europe the following June and July. Icebergs drifted into the major Atlantic sea lanes. Current estimates show such effects also would occur from a major nuclear conflict and could last for up to several years due to an enormous volume of tiny particles being thrust into the upper atmosphere.

Nothing quite so dramatic would be required, however. The exact number and size of nuclear explosions would need to be worked out, but, assuming a 1-2° tolerance for upwardly moving mercury before we would need another quota of nuclear cooling, it seems reasonable to anticipate that a mere 50 or so atomic or hydrogen detonations every 4-5 years, strategically located, should do the trick. (Or, if preferred, the same result might be achieved with only about 10 thermonuclear detonations annually, indefinitely into the future.)

Initially, ground zero might be countries where there is already a perceived need for regime change, particularly if the prevailing landscapes there would lend themselves to the lifting into high atmosphere of massive amounts of debris, such as the huge tonnage of silica micro-particles that might be generated from common forms of desert sand caught on the fringes of nuclear explosions.

Next, we might consider using the enormous wastelands of the American west, many already depleted of oil or natural gas resources and offering few advantages to the population as a whole. Surely some accommodation could be made with Indian nations currently dwelling in some of these desolate regions. Nuclear blasts there could be repeated almost endlessly without disrupting the lives of busy urban commuters, highly paid political contributors, farmers or ranchers in more habitable parts of the country, or the majority of the electorate.

Given the enormously redundant supplies of nuclear weapons already being maintained at great cost but to nobody's advantage, it is likely that a nuclear cooling program could be sustained for generations, perhaps longer, without much addition to budget deficits.

In the interim, our species could gradually wean itself of the harmful forms of energy generation or transportation that produce global warming. Meanwhile too, politicians might have a chance to see the benefits of a more progressive approach to climate change than our simply putting more and more carbon dioxide into the air.

The Atmospheric and Climatic Consequences of Nuclear War. Carl Sagan in "The Cold and the Dark: The World After Nuclear War (10/31/83)," at mindfully.org.

Climate Effects of Volcanic Eruptions, at the Department of Geological Sciences, San Diego State University web site.

Climate 'would reel from A-bombs.' Jonathan Amos in BBC News, 12/12/06

The Dangers from Nuclear Weapons: Myths and Facts. Nuclear War Survival Skills at oism.org.

Small Nuclear War Would Devastate Global Climate, Scientists Warn. Richard A. Lovett in National Geographic News, 12/13/06.