UN experts are meeting to determine the risks which climate change poses to some of the world's special places. The UN's cultural and scientific wing Unesco says climate change threatens World Heritage Sites such as the Great Barrier Reef and the Tower of London.

The two-day meeting aims to develop plans of action to mitigate the threat. Environmental groups want such action to include pledges to reduce emissions, but the US says Unesco has no authority to act on climate change.

In a position paper issued in advance of the Paris meeting, the US says Unesco has no brief to consider anthropogenic climate change as a "threat" to protected sites because it is an unproven theory. Its position appears very different from that of the British government, which is funding the meeting. Under the World Heritage Convention, which Unesco oversees, member nations - and just about every country is a member - vow to protect World Heritage Sites wherever they are located.

Over the last 18 months, environmental groups have lodged petitions with Unesco charging that four Sites are threatened by human emissions of greenhouse gases. They include: Sagarmatha National Park in the Himalayas the Belize Barrier Reef Huascar�n National Park in Peru Waterton-Glacier International Peace Park on the US/Canada border Petitioners say the natural features of these areas, such as coral, glaciers and wildlife, are threatened by rising temperatures and ocean acidification.

"Due to the effects of climate change, the Belize Barrier Reef can be compared to an eggshell," said Candy Gonzalez of the Belize Institute of Environmental Law and Policy (Belpo).