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. BBC World Service environment reporter Matt McGrath came to Malta to see how the rising waters are making life more difficult here.

He reported about 400,000 people live on 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 caused by global warming are threatening 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 an ancient water supply which has for centuries depended on a vast reservoir of fresh water 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 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, which is pumped up to the surface and then to homes and farms around the island.

The water in the tunnels is fresh. But just a just ten metres below it is salty. And thanks to climate change the brackish water is rising.

Mr McGrath quoted Malta water services engineer Paul Micallef as saying the rising sea will make the galleries very difficult to operate in the future. “According to recent studies the water will rise about 96cm by the year 2100. 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”

And the effects of the increasing salinity are already being felt in some parts of the island. In the beautiful Imselliet valley David and Mary Mallia run an organic farm that produces grapes, citrus fruits and vegetables.

Like many people in Malta, the Mallias use a borehole to extract water for their crops. David says that he’s 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 seawater 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.

Cutting their emissions will not be easy, according to Dr Christopher Ciantar who is responsible for environmental policy in 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 seas 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, Mr McGrath concluded.