By Matt McGrath
Environment reporter, BBC World Service
Later this week, scientists on the Intergovernmental Panel on Climate Change will report on how global warming will impact the world now and in the future.
Rising sea levels could cause increased flooding throughout the world, affecting the lives of millions of people.
Rising sea levels are likely to affect Malta
BBC World Service environment reporter Matt McGrath has been to Malta to see how rising waters could make life more difficult on the Mediterranean island in future.
About 400,000 people live on the tiny island of Malta. It is one of the most crowded spaces in the world.
It is also highly vulnerable to climate change. Rising sea levels in the Mediterranean over the next century caused by global warming threaten to submerge parts of the island.
But there is another aspect to sea level rise that is already having a significant effect on Malta. It is the impact on the supply of drinking water.
In the tourist season Malta's population trebles. All these extra people put great pressure on the island's water supply, which depends on a vast reservoir that lies under the island.
Because the fresh water is less dense than salt water, this reserve effectively floats on the sea.
Down the centuries, the Maltese have developed a clever system of underground tunnels, called galleries, to extract the water for human consumption.
About 97m (320ft) beneath the surface of the island lie the Ta' Kandja galleries. Reached by a lift, the tunnels stretch out for several kilometres like the spokes of a wheel, all half-filled with water that is pumped up to the surface and then to homes and farms around the island.
The water in the tunnels is fresh. But just 10m below, it is salty. And thanks to climate change the brackish water is rising.
And the Malta water services engineer Paul Micallef says the rising sea will make the galleries very difficult to operate in the future.
The Ta' Kandja galleries supply fresh water to the inhabitants
"According to recent studies, the water will rise about 96cm by the year 2100," he told the BBC.
"This will affect the availability of groundwater as the interface between sea water and fresh water will actually rise by about 1m and the high salinity levels will be close to our extraction sources."
The effects of the increasing salinity are already being felt in some parts of the island. In the beautiful Im'selliet valley, David and Mary Mallia run an organic farm that produces grapes, citrus fruits and vegetables.
Like many people on Malta, the Mallias use a bore hole to extract water for their crops. David says that he has noticed changes in the water in recent months.
"Since the rainfall has become less, the salinity is becoming higher and higher. Normally in winter, it would be about 2,000 microsiemens, which is a measure of salinity.
"This year, with the lack of rain, it went up to 4,000. It's not good for irrigation. If you water your trees with this water, it will kill them."
Because the rising sea is poisoning their ground water with salt, the authorities in Malta are investing in desalination to make the sea water drinkable. More than half the potable water on the island is now produced in this way.
But desalination plants contribute significantly to global warming as they are powered by fossil fuels. As a member of the European Union, the Maltese are already facing sanctions for failing to co-operate on carbon cutbacks with Brussels.
A bore hole is used to extract water for crops on the Mallias' farm
Cutting their emissions will not be easy, according to Dr Christopher Chaintor who is responsible for environmental policy within the Maltese ministry of rural affairs and the environment.
He says that the people of Malta will want to see climate change impacts first before they are willing to spend money changing their lifestyles.
New predictions for the Mediterranean area suggest that heat waves and droughts will become much more common - and the sea will continue to rise.
To deal with these problems, the EU says that serious emission cuts must be made across Europe. These cutbacks could hamper Malta's tourist industry - and that is an option few local politicians would like to embrace.