Washington, Sept 28 : Carbon dioxide did not cause the end of the last ice age, according to new study by a University of Southern California geologist.

Deep-sea temperatures rose 1,300 years before the rise in atmospheric CO2, ruling out the greenhouse gas as driver of meltdown, Lowell Stott said in his study published online Sept 27 in Science Express.

“There has been this continual reference to the correspondence between CO2 and climate change as reflected in ice core records as justification for the role of CO2 in climate change. You can no longer argue that CO2 alone caused the end of the ice ages,” Stott said.

He said the finding suggested that the rise in greenhouse gas was likely a result of warming and may have accelerated the meltdown – but was not its main cause.

“I don’t want anyone to leave thinking that this is evidence that CO2 doesn’t affect climate. It does, but the important point is that CO2 is not the beginning and end of climate change,” Stott added.

He said while an increase in atmospheric CO2 and the end of the ice ages occurred at roughly the same time, scientists have debated whether CO2 caused the warming or was released later by an already warming sea.

He said the best estimate from other studies of when CO2 began to rise is no earlier than 18,000 years ago, yet the new study has shown that the deep sea, which reflects oceanic temperature trends, started warming about 19,000 years ago.

“What this means is that a lot of energy went into the ocean long before the rise in atmospheric CO2. But where did this energy come from? Evidence points southward. Water’s salinity and temperature are properties that can be used to trace its origin – and the warming deep water appeared to come from the Antarctic Ocean,” he said.

He said this water was then transported northward over 1,000 years via well-known deep-sea currents, a conclusion supported by carbon-dating evidence.

In addition, deep-sea temperature increases coincided with the retreat of Antarctic sea ice, both occurring 19,000 years ago, before the northern hemisphere’s ice retreat began, Stott wrote in his study.

The final evidence, he said, was the correlation between melting Antarctic sea ice and increased springtime solar radiation over Antarctica, suggesting this might be the energy source.

“As the sun pumped in heat, the warming accelerated because of sea-ice albedo feedbacks, in which retreating ice exposes ocean water that reflects less light and absorbs more heat, much like a dark T-shirt on a hot day,” the study said.

Stott said, that in addition, his model has also shown how changed ocean conditions may have been responsible for the release of CO2 from the ocean into the atmosphere, also accelerating the warming. (With inputs from ANI)