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Glacial retreat during last Ice Age was caused by increased levels of greenhouse gases

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Posted August 24, 2015

Climate change is still a very hot topic, as world leaders cannot decide on strict regulations to reduce emissions of greenhouse gasses. However, it is still debated in the academic community as well, because it is not clear if climate change can be stopped at all and what accounts the most for it.

Our glaciers are melting and human actions are at least partly responsible for that. It was confirmed by this new study which demonstrates how increasing levels of greenhouse gases were the main force behind glacial retreat during the last Ice Age. Image credit: oregonstate.edu

Our glaciers are melting and human actions are at least partly responsible for that. It was confirmed by this new study which demonstrates how increasing levels of greenhouse gases were the main force behind glacial retreat during the last Ice Age. Image credit: oregonstate.edu

But now scientists from Oregon State University, Boston College and other institutions have performed a research about glacial retreat during last Ice Age and found it was due to rising levels of carbon dioxide and other greenhouse gases, as opposed to other types of forces.

This knowledge confirms rather dark and sad predictions – most of the world’s glaciers may disappear in the next few centuries during future glacial retreats. It is because of the simple fact that carbon dioxide levels are now significantly higher than they were at the time when the last big glacial retreat happened during the last Ice Age. It is because of the Industrial Revolution and other human activities, which mean now dangerous amounts of greenhouse gases may cause glaciers to melt quicker. This new research tackled some of the uncertainties about glacial melting that were raised because of misinterpretation of data from some of the boulders, which were uncovered more than 11,500 years ago.

Professor Peter Clark, one of the authors of the study, explained that only the increase in carbon dioxide and other greenhouse gases could have caused the glacial retreat at the end of the last Ice Age and not some kind of other forces. He said – “This study validates predictions that future glacial loss will occur due to the on-going increase in greenhouse gas levels from human activities”. He also noted that “we could lose 80-90% of the world’s glaciers in the next several centuries if greenhouse gases continue to rise at the current rate.”

Of course, losing glaciers is not just losing amazing creations of nature. It will cause rising sea levels and, in some cases, have impacts on local water supplies. And current carbon dioxide emissions are much higher than those that caused the last Ice Age to come to an end. The ending period of the last Ice Age started around 19,000 years ago and lasted for about 7,000 years. At that time the levels of carbon dioxide in the atmosphere increased from 180 parts per million to 280 parts per million. But only in the last 150 years the levels of carbon dioxide have increased from 280 to about 400 parts per million.

New findings were made because scientists recalculated the ages at which more than 1,100 glacial boulders from 159 glacial moraines around the world were uncovered from the ice after being buried for thousands of years.

Dating when rock is uncovered to the atmosphere is pretty common in science. When boulders are exposed to cosmic rays, cosmogenic nuclides are produced. And they can be used to measured and used calculate the time of exposure. However, now this dating method is more advanced. Now scientists made new calculations and found the rise in carbon dioxide levels, which were determined from ancient ice cores, matches up nicely with the time at which glacial retreat took place.

Scientists have been speculating, why these boulders got exposed at that particular time. They were not sure what kind of forces were behind the glacial retreat, because time then boulders got uncovered did not match with the increase in greenhouse gases. Now scientists know that previously performed dating was simply inaccurate and the glaciers began to melt and retreat as soon as the greenhouse gas levels began to rise.

However, scientists are quick to note that on other cases there may be other forces that can cause glacial melting on a local or regional scale. For example, glacial retreat may be caused by changes in the Earth’s orbit around the sun or shifts in ocean heat distribution. In fact, these factors most likely had effect on the last Ice Age too, but only on a more local case. Global retreat of glaciers was caused by tremendous increase of greenhouse gas levels. This means that in the future we may expect something similar happening on our current glaciers as well, which will definitely cause some major problems.

Source: oregonstate.edu

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