Carbon dioxide ended last Ice Age

http://www.theaustralian.com.au/news/health-science/carbon-dioxide-ended-last-ice-age-scientists-new-study-says/story-e6frg8y6-1226319448088

Published in the British journal Nature, the investigation looked at 80 ice cores and sedimentary samples taken from Greenland, lake bottoms and sea floors on every continent.

"Putting all of these records together into a reconstruction of global temperatures shows a beautiful correlation with rising CO2 at the end of the Ice Age," said Mr Shakun.

A rise in carbon dioxide "actually precedes global temperature range, which is what you would expect if CO2 is causing the warming."

The scientists theorise that orbital shift boosted sunlight that warmed the northern hemisphere, causing some of its icesheet to melt and spill gigatonnes of chilly freshwater into the North Atlantic.

The big gush had a dampening effect on a well-known "conveyor belt" of current by which warm water travels northwards on the surface of the Atlantic before cooling and returning southwards at depth.

When the current braked, warm water began to build up in the southern Atlantic, where it swiftly started to warm up Antarctica and the Southern Ocean.

Warming the south in turn shifted the wind and melted sea ice, releasing some of the vast amounts of CO2 that had been absorbed by the ocean and stored in its depths, according to their hypothesis.

Today, CO2 - disgorged by the burning of coal, oil and gas - is again in the frame.

In London last week, 20 winners of the Blue Planet Prize, one of the world's most prestigious green awards, said current emissions of warming gases were so high there was only a "50-50" chance of limiting the temperature rise to three degrees Celsius.

There were "serious risks" of a 5.0 C rise, a temperature last seen on the planet 30 million years ago, they said.

"CO2 was a big part of bringing the world out of the last Ice Age and it took about 10,000 years to do it," said Mr Shakun.

"Now CO2 levels are rising again, but this time an equivalent increase in CO2 has occurred in only about 200 years, and there are clear signs that the planet is already beginning to respond."