The government previously forecast a ``worst-case scenario'' rise in the Thames of 4.2 meters during the highest tidal surges, the agency said today in an e-mailed statement. Research by scientists at the Met Office contributed to a report for the Environment Agency, which manages flood risk.

The downward revision means a tide-excluding estuary barrier isn't likely to be needed, the Met Office said. The river's most likely gain will be 20 centimeters to 90 centimeters due to melting ice sheets and thermal expansion as water molecules become more spaced out due to warmer temperatures, it said, describing the worst-case scenario of 2.7 meters as ``highly unlikely.''

``By narrowing previous uncertainty we now have an improved understanding of how climate change will affect the Thames estuary and can develop realistic and cost-effective options, which will meet future needs,'' Tim Reeder, the Environment Agency's climate change program manager for the Thames region, said in the statement.

The Liverpool-based Proudman Oceanographic Laboratory and the Centre for Ecology and Hydrology, which has offices in six towns, also contributed to the report, titled the Thames Estuary 2100 Project, which was commissioned by the Environment Agency, a government body that operates in England and Wales.

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