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Scientists are also looking for the chemical signature of a “bomb spike” lingering in the backbones of basking sharks to learn more about the sharks’ largely unknown lifestyle. Levels of radioactive carbon-14 in the atmosphere spiked in the late 1950s and early 1960s because of nuclear weapons testing. 14C levels in both the Northern (dark gray) and Southern (light gray) Hemispheres nearly doubled from historical levels until the 1963 Limited Test Ban Treaty prohibited testing in the atmosphere. (Based on GNUPLOT 4.2 patchlevel 2)[back]
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