How do we know if the changes in Earth's climate today are an aberration due to human activities or just one more chapter in a 4.6-billion-year-long story? One way is through the study of cores from ice and ocean sediments. Like tree rings, each layer in the core records conditions about the atmosphere – oxygen isotopes, methane concentrations, dust content, even volcanic eruptions – in the sediment and dead microorganisms such as foraminifera.
The evidence shows that in the 1800s, as the Industrial Revolution took off, atmospheric CO2 concentrations begin an unprecedented upward climb, rising rapidly from 280 ppm (parts per million) in the early 1800s to a current level of 376 ppm. Data from core drilling has also enabled scientists to make a connection between rapid climate change and shifts in ocean circulation patterns.