The island nation of Tuvalu in the Pacific Ocean is being threatened by record high tides this weekend.

The Tuvalu Meteorological Office has warned that much of the main island, Funafuti, may be flooded for up to six hours.

One of the lowest-lying countries in the world, Tuvalu would be most at risk from rising sea levels were they to result from a major warming of the planet.

No point in Tuvalu is more than 4.5 metres above sea level.

The exceptionally high spring tides this weekend are expected to reach 3.2 metres above normal sea level.

If high winds and waves coincide with the tides, then the vast majority of the land could be swamped.

Thermal expansion

Most scientists believe that the Earth is getting warmer and as it does so may raise sea levels by tens of centimetres over the next century, mainly through the thermal expansion of the oceans.

The government of Tuvalu has been campaigning for years about what it believes to be problems associated with global warming.

It says land has been ruined by the rising sea water and many Tuvalu farmers now grow their taro crops in tins filled with compost rather than the traditional pits.

The council of the United Nations has just voted to admit Tuvalu to be the 189th member of the UN.

This could give the country a better platform from which to campaign about the threat from global warming.

But the real threat from climate change is by no means clear. As climate models have improved, the forecasts of rising sea levels have been revised downwards. There are even scientists who say a warmer world could actually lead to quite dramatic falls in sea levels.