"Speaking at the American Chemical Society meeting in San Francisco, chemist Graham Jones said that prior to the 1940s, all the carbon-14 in the Earth’s biosphere was produced by cosmic rays and nitrogen in the upper atmosphere. However, from the late 1940s to 1963, atomic bomb tests released radioactive material and significantly increased the amount of carbon-14 in the atmosphere. Ever since the atomic tests stopped in ‘63, this “bomb-pulse” C-14 has been gradually diluted by the CO2 formed by the burning of fossil fuels" - τorƍue