'In the past, the boundaries between geological ages are marked by sudden losses of species. We may now be entering a new age in which climate change and other human-caused factors such as fishing are the major threats for the oceans and their life,' the researchers said.

Man-made carbon emissions are now above the 'worst case' scenario envisioned by the Intergovernmental Panel on Climate Change (IPCC), causing the most rapid global warming seen since the peak of the last Ice Age.

'At current emission rates it is possible we will pass the critical level of 450 parts per million carbon dioxide in the atmosphere by 2040. That's the level when, it is generally agreed, global climate change may become catastrophic and irreversible,' the researchers said. 'At that point we can expect to see the loss of most of our coral reefs and the arctic seas.'

Scientists expect ocean oxygen levels to decline by about six percent for every one degree increase in temperature and areas in the sea which are low in oxygen to grow by at least 50 percent.

These findings were published in the latest issue of Current Biology.