By Richard Black
Environment Correspondent, BBC News website
UN experts are meeting to determine the risks which climate change poses to some of the world's special places.
Unesco says human-induced climate change is harming Everest
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.
Four degrees of risk
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.
Petitioners say the natural features of these areas, such as coral, glaciers and wildlife, are threatened by rising temperatures and ocean acidification.
- Sagarmatha National Park in the Himalayas
- the Belize Barrier Reef
- Huascarán National Park in Peru
- Waterton-Glacier International Peace Park on the US/Canada border
"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).
"It is fragile and needs special care; losing the wonder and beauty of the Reef for future generations because of short-term gain and greed would be too painful to bear."
But Unesco itself goes further.
As well as adding Australia's Great Barrier Reef, Greenland's Ilulissat Ice Fjord, and Mount Kilimanjaro to the global list of threatened beauty spots, it also says that World Heritage Sites built by human hand are compromised by human emissions.
Floods, it says, threaten the Tower of London and other sites in the UK capital as well as Venice, while the Great Mosques of Timbuktu and the prehistoric megalithic temples of Hagar Qim in Malta risk damage, perhaps even collapse, from desertification and changes to rainfall and temperature.
In the case of Sagarmatha, campaigners say global warming brings direct risks to the human population by increasing the risk of catastrophic flooding.
"This meeting is very important for the people of Nepal, as well as for all the people of the world," said Prakash Sharma, director of Pro Public (Friends of the Earth Nepal).
"I strongly believe the expert group will recommend all the necessary steps required to reduce the threat of glacier lake outburst floods and to protect the livelihoods of the Sherpa people."
However, the US contends Unesco has no remit to take protective action unless the nation where the site under threat is located has consented to such action.
So far, none of the countries involved has made such a declaration.
The two-day meeting will propose a list of actions which should be put forward for adoption at the annual World Heritage Committee meeting, to be held this July in Vilnius.