And a separate paper in IOP Publishing’s journal Environmental Research Letters warned that increasing acidity in the seas could damage fish, corals and shellfish – leaving fishing communities facing economic disaster.
The researchers from Woods Hole Oceanographic Institution, Massachusetts, said emissions from deforestation and burning of fossil fuels had increased levels of CO2 in the atmosphere by almost 40% above pre-industrial levels.
Currently around 30% of the CO2 put into the atmosphere by human activities is absorbed by the oceans where it dissolves, altering the chemistry of the surface sea levels making it more acidic.
The acidity can damage wildlife, particularly shell-forming creatures and the species that feed on them, with knock-on effects on people who rely on the oceans for food and livelihoods.
Damage to corals could also reduce the coastal protection from storms that reefs currently provide.
According to the US researchers, there were almost 13,000 fishermen in the UK in 2007, who harvested £645m of marine products, almost half (43%) of which were shellfish.
In the US, domestic fisheries provided a primary sale value of $5.1bn (£3.1bn) in 2007, they said.
The statement from the science academies of 70 countries, warned that despite the seriousness of the problem, there was a danger it could be left off the agenda at Copenhagen.
The joint statement calls on world leaders to explicitly recognise the dangers posed to the oceans of rising CO2 levels, which it warns are irreversible and could cause severe damage by 2050, or even earlier, if emissions carry on as they are.
Martin Rees, president of the Royal Society, said the effect of rising levels of CO2 in the atmosphere on the oceans had not received much political attention.
But he said: “Unless global CO2 emissions can be cut by at least 50% by 2050 and more thereafter, we could confront an underwater catastrophe, with irreversible changes in the makeup of our marine biodiversity.
“The effects will be seen worldwide, threatening food security, reducing coastal protection and damaging the local economies that may be least able to tolerate it.
“Copenhagen must address this very real and serious threat.”