Ice samples produced by drilling in Antarctica show that for hundreds of thousands of years the proportion of greenhouse gases in the atmosphere has not increased as it has due to human activity
One of the ice samples removed from Dome C. The greenhouse gases were detected inside air bubbles trapped in the ice
Samples of ancient ice extracted by drilling in the frozen depths of Antarctica reveal that for at least 650 thousand years the concentrations of three important greenhouse gases did not reach the levels that exist today in the atmosphere due to human activity. The gases in question are carbon dioxide, methane and nitric oxide. The concentrations of these gases in the atmosphere have increased in recent centuries at a much greater rate than before man began to cut down forests and burn coal and other fuels intensively.
The ice drilling and the testing of the samples were done by the "European Antarctic Ice Drilling Program", and the results were recently published in the journal "Science". The greenhouse gases were discovered inside air bubbles trapped in the ice samples, which were extracted with the help of drilling to a depth of almost 3.5 kilometers in a remote area in East Antarctica known as "Dome C".
Experts who were not involved in the research said that the samples provide a vital picture of the changes in the Antarctic atmosphere and climate over time. According to them, the data will help test and improve computer models used to predict how the accumulation of greenhouse gases will affect the climate.
The earliest evidence to date of changes in the concentration of carbon dioxide in the atmosphere, collected in ice cores at the Russian research station in East Antarctica, is from a little more than 400 thousand years ago. "Now the researchers were able to go back another 250 years and found that nature did not go as far as humans," said Richard Ely, a professor of earth sciences at the University of Pennsylvania and an expert on ice samples. "We are changing the world tremendously - far beyond the state it has been in for a very long time."
The new data also provide the first detailed picture of the conditions that prevailed during the Ice Age cycles, which occurred more than 400 years ago. This is a period of time in the two million year history of the Earth, which was characterized by cycles of cold and warm periods, after which, due to some unknown factor, the cold periods became longer and the hot periods shortened, but became more intense. Before and after this transition period, ice samples show, there was always a close relationship between the amounts of greenhouse gases and the temperature.
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