Climate science required the invention and mastery of many difficult techniques.These had pitfalls, which could lead to controversy.An example of the ingenious technical work and hard-fought debates underlying the main story is the use of radioactive carbon-14 to assign dates to the distant past.

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The prodigious mobilization of science that produced nuclear weapons was so far-reaching that it revolutionized even the study of ancient climates.

Nuclear laboratories, awash with funds and prestige, spun off the discovery of an amazing new technique — radiocarbon dating.

The radioactive isotope carbon-14 is created in the upper atmosphere when cosmic-ray particles from outer space strike nitrogen atoms and transform them into radioactive carbon.

Some of the carbon-14 might find its way into living creatures.

After a creature's death the isotope would slowly decay away over millennia at a fixed rate.

Thus the less of it that remained in an object, in proportion to normal carbon, the older the object was.By 1950, Willard Libby and his group at the University of Chicago had worked out ways to measure this proportion precisely.Their exquisitely sensitive instrumentation was originally developed for studies in entirely different fields including nuclear physics, biomedicine, and detecting fallout from bomb tests.(1) Much of the initial interest in carbon-14 came from archeology, for the isotope could assign dates to Egyptian mummies and the like.As for still earlier periods, carbon-14 dating excited scientists (including some climate scientists) largely because it might shed light on human evolution — the timing of our development as a species, and how climate changes had affected that.(2) It was especially fascinating to discover that our particular species of humans arose something like 100,000 years ago, no doubt deeply influenced by the ice ages.(3) A few scientists noticed that the techniques might also be helpful for the study of climate itself.From its origins in Chicago, carbon-14 dating spread rapidly to other centers, for example the grandly named Geochronometric Laboratory at Yale University.The best way to transfer the exacting techniques was in the heads of the scientists themselves, as they moved to a new job.