BEIJING, Nov. 25-- Sea levels are rising twice as fast as they were 150 years ago and surge in greenhouse emissions are the main cause, US researchers have warned.

The oceans will rise nearly half a metre by the end of the century, forcing coastlines back by hundreds of metres, the researchers claim.

Researchers at Rutgers University in New Jersey analysed cores drilled from different sites along the eastern seaboard.

By drilling down 500 metres through layers of different sediments and using chemical dating techniques, the scientists were able to produce a new sea level record spanning 100 million years.

The analysis, published in the journal Science, showed that during the past 5,000 years, sea levels rose at a rate of around 1mm each year, caused largely by the residual melting of icesheets from the previous ice age. But in the past 150 years, data from tide gauges and satellites show sea levels are rising at 2mm a year.

The switch occurred after the mid-19th century, when factories and increased use of coal and later oil started pouring greenhouse gases into the atmosphere, according to the analysis.

A second paper in journal Science, describes the content of the greenhouse gases within the core and shows that carbon dioxide levels today are 27% higher than they have been in the past 650,000 years and levels of methane, an even more powerful greenhouse gas, are 130% higher, said Thomas Stocker, a climate researcher at the University of Bern and senior member of the European ice coring team that wrote two new papers based on the core. Enditem

(Agencies)