In the mid-20th century, a dramatic transformation occurred above Earth’s surface – a transformation that would leave an indelible mark on life, oceans, sediments, and even the human body. The “bomb spike,” a legacy of extensive above-ground nuclear testing during the 1950s, brought about a unique chemical shift in the atmosphere. This shift, while not harmful, has proven invaluable to scientists, offering insights into human history, biological processes, and even the definition of a new geological era.
Unlike the immediate radioactive fallout from the explosions, the bomb spike is a lasting imprint, found everywhere from human teeth to the deepest ocean trenches. This silver lining, as some call it, has become a vital tool for various scientific discoveries.
Initially, these nuclear tests released radioactive material into the atmosphere, including the isotope carbon-14. Overground nuclear testing resulted in nearly double the amount of carbon-14 compared to pre-bomb levels. This isotope found its way into Earth’s various carbon pools, from water to vegetation, and eventually to humans. Walter Kutschera of the University of Vienna describes how bomb carbon-14 has left its mark on every carbon exchange with atmospheric CO2 since the late 1950s.
Scientists eventually recognized the potential of the bomb spike’s imprint. Carbon-14, used previously for radiocarbon dating of ancient remains, offered a new perspective. Unlike its traditional use, bomb carbon-14 allowed dating within the past 70-80 years. By analyzing the carbon-14 proportions in organic matter exposed to atmospheric carbon since the tests, scientists could pinpoint their formation window to within one to two years. This technique even applies to humans. For instance, the amount of bomb carbon-14 accumulated in tissues can indicate a person’s birth era
Beyond dating, the bomb spike has been an indispensable tool in forensic science. From identifying age in unidentified human remains to assisting in investigations of war crimes and genocide, bomb carbon-14 has provided valuable insights. It even helped uncover new knowledge about our bodies and brains. Biologist Kirsty Spalding’s research, utilizing bomb carbon-14 in DNA, revealed the relative ages of our cells, including the discovery of adult neurogenesis – the production of new neurons throughout life. This finding could lead to breakthroughs in medical strategies to prevent neuron loss or promote neuron generation.
The bomb spike’s significance extends even further, shaping the definition of a new geological era, the Anthropocene. Characterized by human impact on Earth, this era’s official start was proposed as the 1950s due to markers like bomb carbon-14 and other nuclear elements. A recent recommendation from the Anthropocene Working Group suggests that Canada’s Crawford Lake holds the golden spike, marking the beginning of this era in sediment layers.
Intriguingly, the bomb spike leaves a mark not only in sediments but also within us. As bomb carbon-14 levels return to pre-atomic levels, our bodies will hold a unique signifier of this pivotal moment in human history, a testament to a time when nuclear bombs and humanity’s profound impact on nature began to reshape the world.