U.S. WEATHER BUREAU PHOTO FIGURE 2.—Generalized drawing of the earth’s atmosphere. ceeeaeOE etacet cee ees regions and one year or somewhatless at the equator. Radioactive debris from nuclear detonations occurring at very high altitudes (about 30 miles and higher) may have a residence half-time of five years or more. Roughly two-thirds of the radioactive particulate debris injected into the lower stratosphere at the north polar regions has been observed to fall in the 30°-60° North latitude zone, where about 80 percent of the world’s population live. Injection at the equatorial regions has been observed to result in a more even distribution between the two hemispheres. For surface bursts of high (million ton range) yield about 50-80 percent of the radioactive debris is deposited as “early fallout,” ie., within 24 hours. Air bursts—wherethe fireball does not approach the surface — result in little, if any, localfallout. Table 2 tabulates some of the key data on estimated nuclear energyyields from all past nuclear weapons tests. Of the total energy released of 511 million tons equivalent of TNT about 70 TABLE 2.—Estimates of Yields from All Nuclear Weapons Tests Total million tons*.....0...0.0 ccc cceceeeatueeeeeens Fission million tons..........0.0.0..cc.cccecceecccueaeeeeeceueeas Fission million tons scattered globally...........00000.... USSR US and UK Totalt 350 141 110 161 82 51 511 193 161 *TNT equivalent. +The French tests have contributed only smali amounts. 749-413 O-64—2 9 G05 % a U 3