Using a combination of computer models and real-world observed data, US scientists said on Thursday they have found the first clear evidence that humans are warming the world's oceans.
This finding will remove much of the uncertainty associated with debates about global warming, said the scientists in a paper published in the online issue of the journal Science.
The researchers, led by Tim Barnett at the Scripps Institution of Oceanography in California, have captured signals of the penetration of greenhouse gas-influenced warming in the oceans, indicating that the warming is produced by human activities.
In this study, Barnett and his colleagues used computer models to calculate human-produced warming over the last 40 years in the world's oceans.
This high degree of visual agreement and statistical significance that leads Barnett to conclude that the warming is 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," said Barnett.
The climate mechanisms behind the ocean study will produce broad-scale changes across the atmosphere and land, the researchers noted.
In the decades immediately ahead, the changes will be felt in regional water supplies, including areas impacted by accelerated glacier melting in the South American Andes and in western China, putting millions of people at risk without adequate summertime water, according to Barnett.
The implications of these results go far beyond identifying the reasons for ocean warming, scientists noted.
"Taking these new results with those obtained in the last few years leaves little doubt that there is a human-induced signal in the environment."
"How to respond to the serious problems posed by these predictions is a question society must decide," they wrote.