There is much debate about global warming and whether it is a natural process or something which man is contributing towards. The discovery of the World’s oldest known DNA samples now adds further weight to the argument that global warming is a natural process.

DNA samples have been retrieved from below a mile-deep cap of ice, revealing a “lost world” that once thrived on Greenland before it froze over. The DNA samples show that Greenland was once covered in a dense forest, full of animals and plants, less than a million years ago. Scientists have analysed the DNA and estimated that it is around 450,000 – 900,000 years old. The DNA is the oldest authenticated DNA taken from biological material.

Greenland is currently house a 2km thick layer of ice. The DNA evidence shows that it once houses a very different environment to the one we see today. Pine, yew and alder trees were found indicating that the climate would be akin to the forests in Canada and Sweden that we see today.

The species of trees found mean that scientists can estimate the types of temperatures that Greenland must have experienced because different trees require different environments in order to survive. The prescence of yew trees meant that winters cannot have had temperatures of less than -17 C, and the prescence of some other varieites of trees show that the summer temperature cannot have been less than about 10 C.

These temperatures show that that area of the world was a lot warmer than previously thought. The discovery also appears to disprove the theory that there was no ice on Greenland around 125,000 years ago when the global climate was around 5C warmer than current temperatures – the study suggests that Greenland’s ice cap has existed for more than 450,000 years.

The age of the ice cap shows that it is far more stable than previously thought and may have implications for how ice sheets respond to global warming. In the last interglacial, sea levels rose by about 6 metres however, if the ice cap didn’t melt, the water must have come from other sources such as Antarctic ice.

However, if man is helping to fuel climate change and the world is already heading for a natural increase in temperature, it could mean that bigger temperature rises than previously thought could occur.

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