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See Inside May 2010

Readers Respond on "Looking for Life in the Multiverse"

Letters to the editor from the January 2010 issue of Scientific American

Nuclear Inferno
In “Local Nuclear War, Global Suffering,” Alan Robock and Owen Brian Toon claim that a nuclear exchange of 100 Hiroshima-size weapons between India and Pakistan would cause a global catastrophe from smoke particles lofted into the stratosphere. How do the authors reconcile the massive amount of smoke pumped into the earth’s atmosphere during World War II?

Toward the end of the war, more than 60 Japanese cities were firebombed. Other areas to consider, of course, are the British, German and Russian cities burned and destroyed during the war, as well as particularly “dirty” bombings like the oil refineries at Ploesti, Romania and numerous major battles. In my opinion, the authors have overstated the global damage from a nuclear war of the type they describe, and perhaps they did not consider thoroughly enough the environmental effects incurred during WWII.
Kevin A. Capps
Corona del Mar, Calif.

THE AUTHORS REPLY: There were indeed numerous fires in Japan and Europe during World War II, several of which occurred near the end of the war.

The observational database from WWII is not adequate to tell if smoke from these fires reached the stratosphere. For the scenario discussed by Capps, over a period of four weeks, 155 square kilometers (60 square miles) of cities burned in Japan. Unless each fire was of a sufficient intensity to produce a firestorm, the smoke would not have been pumped into the stratosphere and would have remained in the troposphere, like the smoke from the oil well fires during the Gulf War in 1991. This means the smoke would have a lifetime in the atmosphere of only about a week, with only small, short-term local effects. Even if all the smoke did get into the stratosphere, the optical depth would have been much less than that from the regional nuclear conflict we studied: the burned area we considered was 1,300 km2. The number of large firestorms in WW II was small compared with the 100 in our study.

Our models suggest that the small number of events in WWII would not have produced climate effects that would have been detectable against the background of natural weather and climate variability. We do not know if there was a small effect on climate from the smoke generated in WWII, because nobody has studied it. Thus, WWII does not give any evidence that our results are incorrect. In fact, the unfortunate example of cities burning supports our theory that large firestorms would follow atomic bombing. More recent studies of large forest and brush fires, such as in Australia during January 2003, do show that smoke can be injected into the lower stratosphere and may be lofted by sunlight to higher altitudes.

This article was originally published with the title "Antimatter Nanotech Safety Firestorms."

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