Bright, Hot, then Cold: The City After Nuclear Blast

Dec 28th, 2016 | By | Category: Arstechnica, Nukes

Nuclear war offers a multitude of bad ways to die. The bulk of the initial deaths from a nuclear bomb come from the intense heat from the detonation itself, followed by the firestorms triggered by the blast. Extrapolating from the incendiary bomb attacks in World War II (Tokyo and Dresden being among the more infamous), the authors note, “the projected number of injured requiring medical treatment would be drastically reduced relative to that projected by blast scaling, as many injured that would otherwise require treatment would be consumed in the fires.” If not vaporized at the center of a blast, many of those who survive the initial moments would then promptly be burned alive by a raging super-fire extending for many kilometers from the hypocenter of the blast.

It’s fascinating to see how scientists struggle to determine what would happen during an extraordinary event–like the detonation of megaton fusion-fission bomb over a contemporary city. There really isn’t data; one is left to take data from other events, stretch and make educated estimates of what a different magnitude event would be like.

How big of a firestorm would result? How much soot would be produced? What color soot? The answers to these questions for a modern nuclear bomb (~ 300 kt range) over a modern American city are tricky–and the key for understanding how many would die, and how deep and dark the subsequent nuclear winter would be.

To answer, scientists have attempted to extrapolate from the firebombing of German and Japanese cities in World War II. For the latter (with extensive paper and wood construction) the data may be an overestimate. German cities were constructed more in line with modern construction techniques. Our cities presently have extensive petrochemical stores (gas stations and the like) as well as much plastic (that didn’t exist in the 1940’s). We’re left with (unsatisfying) broad ranges of possibilities. Perhaps the key point is, all of the reasonable possibilities are horrible.

Why wasn’t there a nuclear winter following all the atmospheric tests of nuclear weapons? The test sites were selected explicitly for the lack of flammable materials to throw up into the atmosphere–a constructed best-case scenario.