Sydney, Aug 11 - There is mounting evidence that human activity is changing the world's oceans in profound and irreversible ways, according to a recent study.

For instance, 'the climate is currently warming faster than the worst case known from the fossil record, about 56 million years ago, when temperatures rose about six degrees over 1,000 years.'

'If emissions continue it is not unreasonable to expect warming of 5.5 degrees by the end of this century,' says the latest study.

The study says that rates of physical change in the oceans are unprecedented in some cases, and change in ocean life is likely to be equally quick.

These include changes in the areas fish and other sea species can inhabit, invasions, extinctions and major shifts in marine ecosystems.

The study was conducted by Mike Kingsford, professor at the ARC Centre of Excellence for Coral Reef Studies and James Cook University and colleague Andrew Brierley of St. Andrews University, Scotland.

Man-made carbon emissions 'are affecting marine biological processes from genes to ecosystems over scales from rock pools to ocean basins, impacting ecosystem services and threatening human food security,' warn the study authors.