According to The Guardian, Marseille, Alexandria and Istanbul find themselves among the cities that are in danger of being struck by a tsunami reaching more than a meter high.

While a little over one meter might not seem like great danger, we have to remember that waves that stand at 1.5 to 2 meters tall can lift cars from the ground. Even shorter ones can prove to be very dangerous as they are essentially water walls travelling at 65 km/h.

The high risk of a tsunami emerging in the Mediterranean Sea is due to rising water levels around the world that are generated by climate change.

Other regions, such as the Pacific and Indian Ocean, are well aware of the risks and dangers posed by the giant waves, which is why communities there are better prepared in case of one showing up. But European coast cities could underestimate the threat, warn UNESCO experts.

The organization says that five at-risk communities in the area will join 40 other "tsunami-ready" cities in 21 countries by the next year, including Cannes and Chipiona.

The "tsunami-ready" program is part of UNESCO's effort launched ahead of the UN Ocean conference, which will take place next week in Lisbon. The organization wants to make sure that everyone that is at risk knows what to do in case of such an event.

Bernardo Aliaga, lead tsunami expert at UNESCO, said that "the tsunamis of 2004 and 2011 were a wake-up call. We have come a long way since 2004. We are safer today. But there are gaps in preparedness and we need to improve; we need to make sure warnings are understood by visitors and communities."

The Indian Ocean tsunami in 2004, which is one of the deadliest in human history, killed about 230.000 people in 14 countries, while the 40 meters tall tsunami that hit Japan in 2011 killed 18.000 people.

UNESCO's Pacific Tsunami Warning Center was set up after the 2004 disaster in order to respond to tsunami events in advance, and it was able to do so for 125 such events.

"The upstream part is in good shape. Work has been done to establish 12 tsunami-warning centers covering most of the ocean, including the Mediterranean", said Aliaga.

The new warning centers include five in the Mediterranean and the north-east Atlantic, some of them being in Greece, France and Italy.

"The risk of tsunami is underestimated in most areas, including the Mediterranean. We need to get the message out. In the Mediterranean, there is no question about it: it is not if, it’s when", he added.

Aliaga mentions that "the link is that sea-level rise increases the impact of tsunamis."

The tsunami expert says that he wants to get as many people from the risk zone as possible ready for a giant wave hitting by the end of this decade.

"We want 100% of communities, where there is a proven hazard, to be ready to respond by 2030. They will have evacuation maps, they will have carried out exercises and they will already have in place 24-hour alerts", he concluded.