Bomb pulse

The bomb pulse is the sudden increase of <a href="/facts/Carbon-14/Ut8SBNNa">carbon-14</a> (14C) in <a href="/facts/Earth%2527s_atmosphere/FV97Am25">Earth's atmosphere</a> due to the hundreds of above-ground <a href="/facts/Nuclear_tests/s2srGDFP">nuclear tests</a> that started in 1945 and intensified after 1950 until 1963, when the <a href="/facts/Limited_Test_Ban_Treaty/vhF6shhg">Limited Test Ban Treaty</a> was signed by the United States, the Soviet Union and the United Kingdom. These blasts were followed by a doubling of the relative concentration of 14C in the atmosphere.
Measurements of 14C levels by mass spectrometers are most accurately made by comparison to another carbon isotope, often the common isotope 12C. The figure shows how the relative concentration of 14C in the atmosphere, of order only 1 part per 1012, changed following the <a href="/facts/Trinity_(nuclear_test)/0aHtpyUN">first bomb test in 1945</a>. The increase in atmospheric 12C since 1955 has reduced the relative concentration of 14C to pre-1955 values, even though the absolute 14C concentration remains elevated.
14C naturally develops in trace amounts in the atmosphere and can be detected in all living things. Carbon of all types is continually used to form the molecules of the <a href="/facts/Cell_(biology)/bLM9UQvy">cells</a> of organisms. Doubling of the concentration of 14C in the atmosphere is reflected in the tissues and cells of all organisms that lived around the period of nuclear testing. This property has many applications in biology and <a href="/facts/Forensics/4upVa2vB">forensics</a>.

Bomb pulse open-in-new

Bomb pulse