Factory smoke Photo: MARTIN POPE
A new study suggests bigger cuts in carbon dioxide (CO2) emissions may be needed to prevent drastic long term climate change.
The evidence was obtained by scientists looking back three million years to the Pliocene epoch, when global temperatures were 5.4F (3C) to 9F (5C) higher than they are today.
They found that levels of CO2 in the atmosphere at the time should not have produced such a warm world.
Climate models used to predict modern levels of man-made global warming, temperatures in the mid-Pliocene should have been lower.
The findings suggest the Earth’s temperature may be 30 per cent to 50 per cent more sensitive to atmospheric carbon dioxide than experts have assumed.
The discrepancy can be explained by long term changes in vegetation and ice cover.
Ice reflects solar radiation back into space and therefore helps to prevent the Earth heating up. When ice melts and disappears this “albedo” effect is lessened, contributing to a rise in temperature.
Vegetation absorbs carbon dioxide but also keeps the Earth warm by preventing heat reflection.
The scientists compared temperature reconstructions from sediments in the ocean floor with a global climate simulation model which aimed to map climate three million years ago.