The latest calculations on the effects of regional nuclear conflict (“Regional Forecasts,” May/June 2007 Bulletin) are reminiscent of an important shock of the 1980s: the concept of “nuclear winter.” At the time it was thought that a few hundred nuclear detonations in the megaton range on highly combustible targets such as cities and oil refineries could cause prolonged global cooling and loss of sunlight, and catastrophic impacts upon food supplies.

Thanks to these new simulations, we now know that even a detonation of around 100 “small” nuclear weapons of the size used on Hiroshima (12- to 15-kiloton range) could trigger a cooling effect larger than that witnessed during the pre-industrial Little Ice Age.

This is a shocking reminder of the devastating potential of even relatively low-yield nuclear weapons. But it is significant that the new research does not address the potential impact of larger weapons belonging to major nuclear powers such as Britain, France, Russia, China, or the United States. Perhaps the researchers wanted to distance themselves from implied criticism of U.S. nuclear strategy and policy?

Using their figures and applying well-known scaling laws, it is possible to make some first-order approximations of the destructive potential of some of the bigger nuclear weapons out there. Consider one Trident nuclear missile submarine: The British variant has 16 missiles with 48 independently targetable 100-kiloton warheads. One 100-kiloton warhead is approximately eight times the size of the Hiroshima bomb and would cause blast and fire effects over four times the area. Crudely, then, the area impacted by 48 100- kiloton warheads would be equivalent to 192 Hiroshimas. This is already nearly twice the impact of the scenario used in these latest nuclear winter simulations, and in fact, is likely to be an underestimation because a key effect, widespread fires, are particularly significant for larger-scale nuclear detonations.

The aforementioned estimates utilize blast and fire casualty predictions developed by the now-defunct U.S. Office of Technology Assessment (OTA). The fire spread model developed by Theodore Postol at MIT predicts that fires are likely to rage over areas some three and a half to four times larger than OTA estimates. Taking this into account, one British Trident submarine has the destructive potential of 768 Hiroshima-type explosions. This is roughly seven times the level predicted by the new simulations of regional conflict in India and Pakistan, making it clear that just one British submarine with a full complement of Trident nuclear missiles has the potential to trigger significant and long- lasting global cooling.

The major nuclear powers need to be challenged to respond to these findings. It suits us to focus our thoughts on the global war on terror or regional conflicts rather than on our own hypocritical policies and actions as we silently threaten nuclear obliteration every day.

This information must move out of the technical journals and into mainstream debate and media, and be used to shake people out of a state of complacency about the threat posed by our own nuclear weapons. Armed with the facts, most people could not be persuaded to pay for several global doomsday machines called Trident.

We must challenge the nuclear powers to reduce warhead numbers to a few tens at most and to take the rest off patrol and alert, and put them into verifiable secure storage with inspection. In Britain, this should be a major new component in the “Rethink Trident” campaign.