Snow falling seasonally in Greenland and Antarctica or on glaciers around the globe is slowly compressed into ice and during this process, bubbles of air remained trapped in the ice. Scientists and researchers, using ice cores, are able "to read" these bubbles and thus to measure the concentration of gases, including the one of CO2 for a specific period of time.Ice cores are created drilling the ice pack as shown in the picture underneath.
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| Researcher Margarita Marinova uses an auger to drill a core from the ice pack Credit: Jennifer Heldman, National Science Foundation (NSF) |
The layers of ice accumulating in the coldest regions of Earth become thus a sort of paper where scientists can read the type of atmosphere characterising other times. Ice core records allow us to get continuous reconstructions of past climate, going back a minimum of 800,000 years in the history of world's ancient amosphere. By watching past concentrations of greenhouse gases in layers in ice cores, scientists can calculate how modern amounts of CO2 and methane compare to those of the past, and, essentially, compare past concentrations of greenhouse gases to temperature.