Ocean depths reveal secrets

Australian scientists hope a groundbreaking study that plumbed the ocean depths to record sea temperatures over millions of years will shed some light on climate change.

Canberra scientist Sindia Sosdian and research partner Yair Rosenthal studied the shells of tiny sea creatures for more than three years to examine major climate shifts over the past 3.2 million years.

The research recorded two major cooling periods over that time - the first about 2.7 million years ago when a drop in greenhouse gases is believed to have caused the formation of giant ice sheets in the Northern Hemisphere.

The pair also uncovered another significant change in temperatures more than a million years later not yet explained by scientists.

Dr Sosdian believes the information can help climate change specialists better interpret ancient shifts in temperatures.

She also believes the ice sheets had a much bigger impact on global temperatures than first thought.

"Our finding suggests that the way ice grows and retreats - its physical dynamics - played a significant role in hastening climate transitions the second time around," she said.

The research also recorded an overall cooling of deep ocean temperatures by 3C, backing up a long-held view.

"We know ... there's just been a long-term cooling trend, but we're not quite sure what's caused that," she said. The study has been published in the international journal Science.

- NZPA/AAP