Global warming is creating a climate time bomb by storing enormous amounts of heat in the waters of the north Atlantic, UK scientists have discovered.
Marine researchers at Southampton and Plymouth universities have found that the upper 1,500 metres of the ocean from western Europe to the eastern US have warmed by 0.015C in seven years. The capacity of the oceans to store heat means that a water temperature rise of that size is enough to warm the atmosphere above by almost 9C.
Neil Wells, a scientist on the project at the National Oceanographic Centre in Southampton, said: "People might think it doesn't sound like a big temperature rise but it's very significant." The findings were announced in the journal Geophysical Research Letters as James Lovelock, the UK scientist who developed the gaia theory of life on Earth, warned that such ocean warming could stifle marine life and accelerate climate change.
Professor Lovelock said that thermal mixing of water and nutrients shuts down when the upper layer of ocean water reaches about 12C. "That's why the tropical waters are clear blue and the water in the Arctic looks like soup," he said. Such a change would affect marine life, which research suggests could help form clouds over the oceans. Warmer waters would receive less protection from sunlight, which would warm them further.
The Southampton and Plymouth study suggests heat stored in the oceans could be released into the atmosphere in future, tempering efforts to stabilise global temperatures with cuts in manmade greenhouse gas emissions.
The scientists used 200 floats spread across more than 9m square miles of the north Atlantic in 1999 to measure the water's temperature profile accurately for the first time. The floats, part of a worldwide network called Argo, sink to about 2,000 metres and return to the surface every 10 days to transmit their data.
Dr Wells said the floats revealed that Atlantic waters closer to the surface between the UK and the US had warmed much more than the average 0.015C figure.
Speaking before a lecture to the Institution of Chemical Engineers, Prof Lovelock repeated the prediction, made in his recent book The Revenge of Gaia, that global warming will kill billions of people this century. He said the Earth was undergoing a rapid transition that could boost temperatures by 8C, making large parts of the surface uninhabitable and food production impossible. A hotter planet might be able to support less than a tenth of its 6bn population.
"We are not all doomed," he said. "An awful lot of people will die, but I don't see the species dying out."
Scientists say global warming, due to unrestricted carbon emissions from burning fossil fuels, could boost average temperatures by up to 6C by the end of the century, causing famine and violent storms. But they also say that action now to cut greenhouse emissions could stop atmospheric concentrations of carbon dioxide reaching 450 parts per million - equivalent to a temperature rise of 2C from pre-industrial levels. But Prof Lovelock said temperature rises of up to 8C were built in. "Trying to take the job on of regulating the Earth is as crazy as you can get," he said. "We have to adapt."