Experts at Scripps Institution of Oceanography at the University of California and their colleagues claim that their study, which clearly shows that human activity has caused the world’s oceans to warm up, will remove much of the uncertainty hanging over the global warming debate.

Lead researchers Tim Barnett and David Pierce used a combination of computer models and real-world “observed” data to capture signals of warming in the oceans caused by greenhouse gases.

But the results, the authors say, clearly demonstrate that the warming is caused anthropogenically, or through human activities.

For the study, warming in the world’s oceans was measured over the last 40 years. In all the ocean basins, the warming signal found in the upper 700 metres predicted by the models corresponded to the measurements obtained at sea with confidence exceeding 95%.

The correspondence was particularly strong in the upper 500 metres of the water column, which led the scientists to conclude that the warming was the product of human influence.

Efforts to explain the ocean changes through naturally occurring variations in the climate or external forces, such as solar or volcanic factors, did not come close to reproducing the observed warming.

“This is perhaps the most compelling evidence yet that global warming is happening right now and it shows that we can successfully simulate its past and likely future evolution,” Dr Barnett said, adding that he was stunned by the results, which clearly showed the penetration of the warming signal in all the oceans.

“The statistical significance of these results is far too strong to be merely dismissed and should wipe out much of the uncertainty about the reality of global warming.”

According to Dr Barnett, the climate mechanisms behind the ocean study will soon produce huge changes both on land and in the atmosphere. In the decades immediately ahead, these changes will be felt not just internationally but on a regional level.

Water supplies will be impacted by accelerated glacier melting, and millions of people will be put at risk without adequate summertime water. One model also predicted that climate change would likely alter western snow pack resources in the western states of America, as well as its hydrological cycle, causing a water crisis within 20 years.

“The ocean study, taken together with the numerous validations of the same models in the atmosphere, portends far broader changes,” Dr Barnett continued. “Other parts of the world will face similar problems to those expected, and being observed now, in the western US.”

He said that this breakthrough evidence must not be ignored by world leaders, especially those currently not putting climate change at the top of their agenda, like best friend to the polluting industries President Bush and Australian Premier John Howard.

“These scenarios have such a high probability of actually happening that they need to be taken very seriously by decision makers,” he warned.

By Jane Kettle

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