The event horizon

As these lines are written some 16,000 nuclear weapons are ready for launch worldwide. The details of a nuclear coup-de-grace may never be known. Once global communication channels break down, historians, should such survive, would not know exactly what took place—was it an accidental missile launch triggered by a computer glitch or by radar error, or a deliberate preventive strike following a use-them-or-lose-them strategy, where even a limited strike can trigger a near-total response. As cable and satellite communication cease and television, mobile phone and radio channels break down the hapless members of H. sapiens, having lived for more than 70 years under a nuclear Damocles Sword, would only be able to guess what has transpired. An attack on an urban population by 100 one-megaton weapons would kill up to 20% of the population through blast, heat, ground shock and neutrons and gamma rays, while an attack by 1000 one-megaton weapons would kill immediately almost half the population. Further deaths would occur from fires, lack of medical attention, starvation. Long-lived strontium-90 or cesium-137 would contaminate hot spots and enter the food chain causing internal damage. For survivors of a nuclear war, this lingering radiation hazard could represent a grave threat for as long as 1–5 years after the attack. Whereas models of nuclear war and nuclear winter, such as by Turco, Sagan and others have a large margin of error, the scale of a global or even large regional nuclear conflict can only lead to the largest calamity the human species has ever endured. Survivors of a nuclear event would emerge into an initially cold and subsequently further warming lands encroached by rising oceans.