Ice cores are cylinders of ice that results in a sample of snow and ice accumulation over several years and which are obtained by drilling an ice sheet or glacier. Most ice core records come from Antarctica and Greenland, and the longest ice cores extend to
3km in depth.
The ice cores contain information about various aspects of the past, such as greenhouse gases concentration (CO2 and CH4) and the presence of isotopes [1] which allow us to infer conclusions about the past temperature and investigate climate changes over time.
When the ice forms, small air bubbles become trapped in it. This give to us samples of the atmosphere of the that time. From the analysis of these bubbles it is possible to directly measure the concentration of carbon dioxide - CO2, and methane - CH4 in the atmosphere of that time.
Through comparison between Antarctica ice cores (ie. Law Dome and South Pole) and taking into account the necessary precautions to ensure the results were not affected by other impurities, it was found that the concentration of carbon dioxide (CO2) has been stable over the last millennium until the early nineteenth century. It then started to rise and currently it’s concentration is nearly 40% higher than it was before the industrial revolution. The concentration of Methane (CH4) over the last two centuries also shows an unprecedented rise. Its concentration is now more than double its pre-industrial level.
[1] isotope - two atoms of the same chemical element with different mass numbers and equal atomic numbers.
Source:
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Steffensen, J. P., Andersen, K. K., Bigler, M., Clausen, H. B., Dahl-Jensen, D., Fischer, H., ... & Masson-Delmotte, V. (2008). High-resolution Greenland ice core data show abrupt climate change happens in few years. Science, 321(5889), 680-684. doi: 10.1126/science.1157707
Author: Patricia Azinhaga