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.
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.