Every year the worldwide sea level rises about 3 mm. That doesn’t sound like much, just a little over a 1/10 of an inch, but even that small rise spread out over the entire ocean is a lot of water. Multiply that over years and decades, factor in an increased rate of rise (thanks to our growing addiction to carbon), and you’ve got yourself a radically changing landscape. Literally. There are around a million miles of coastline in the world and a little less than half of the world’s 7 billion inhabitants live within 100 miles of the ocean. Those two factors line up to put a lot of people and lot of places in the crosshairs of rising sea levels.

And if science and hindsight have showed us anything, it’s that our predictions on the negative impacts of climate change have, if anything, been too conservative. The three-foot rise in seas being forecasted for 2100 by the United Nation's Intergovernmental Panel on Climate Change could easily turn into five or six feet. Or 10. There’s a lot of methane locked up in permafrost that could speed up the clock as warming temperatures thaw the ground.

Climate change poses the largest threat to the world's most famous heritage sites, according to a recent report from the United Nations. Cultural and natural sites like Venice and the Statue of Liberty are among the places most at risk.

An earlier study estimated that 20 percent of the 720 UNESCO World Heritage Sites could face a grim future if temperatures rose 5.4 degrees Fahrenheit over the next 200 years. With the rate we’re pumping CO2 into the air and the lagging effects of greenhouse gases (we will be dealing with the CO2 we release into the air today for years), that 5.4 degrees is firmly within the bounds of being a fair scenario and the resulting rising seas could swallow up world treasures like the Statue of Liberty and the Sydney Opera House.

We combed through the list of potentially affected World Heritage Sites and picked out a few to highlight here in addition to a couple of our choices. This is serious business — for every one site in danger on our list, there are another 79 facing circumstances just as dire, along with billions of people and thousands of towns and cities.

Knowledge is power, so take a few minutes and read up on some of the things we could lose if we can’t turn this climate change thing around.

Sydney Opera House

Sydney Opera House The Sydney Opera House is fighting the waters of the Tasman Sea. (Photo: Hai Linh Truong/flickr)

The Sydney Opera House is one of the most iconic performance arts facilities in the world. Perched on Sydney Harbor, it hosts more than 1,500 performances and is visited by millions of people each year. Planning for the Opera House began in the late 1940s with the winning design, by architect Jørn Utzon, chosen in 1957 and construction under way two years later.

It’s the aforementioned location of the Sydney Opera House that puts it at risk to rising sea levels. It’s far enough into the Sydney Harbor that one could suppose an expensive system of emergency barricades could protect it from rising storm surge, but you can’t keep out the ocean for every long. As sea levels rise, it won’t be too long before the Sydney Opera House finds the waters of the Tasman Sea vying for a seat at the next performance.

Statue of Liberty

statue-of-liberty The pedestal gives the Statue of Liberty some breathing room from the rising waters. (Photo: Jon Dawson/flickr)

The Statue of Liberty was well named. The towering statue, a gift given in the late 1800s to the United States by France, overlooked the entry of millions of immigrants steaming into New York Harbor on their way to new lives as Americans. It has become an enduring symbol of our nation and is one of the most popular tourist destinations in New York City, a city thick with world-class tourist destinations.

But like the Sydney Opera House, the Statue of Liberty sits right at sea level overlooking New York Harbor on Liberty Island. Rising seas will eventually swallow that island. The statue itself has a lot of breathing room — the pedestal upon which it stands is 150 feet high — but we could be within a generation or two of seeing the waters lap up to the base of of the pedestal. The world will be a very different place by the time that happens.

Venice

venice, italy Venice has both rising sea levels and sinking ground waters. (Photo: Hernán Piñera/flickr)

It’s easy to see how fragile a grip the city of Venice has in a world of rising seas. Venice sits on a group of 118 islands and is best known for its network of canals running throughout the historic streets. Connected to the mainland by a bridge and protected from the Adriatic Sea by a pair of thin barrier islands, Venice is a city of the water. Boats move people and goods around its canals while diners eat lunch overlooking it all.

Venice has to deal with not only rising sea levels, but also sinking ground levels. Researchers at the Scripps Institution of Oceanography at the University of California estimated that the city is sinking up to two millimeters per year, almost as much as the seas are rising. That one-two punch could end up causing the death blow to Venice as the calendar ticks towards 2100.

Robben Island

robben-island Robben Island is no more than 15 feet above sea level. (Photo: Jameson Fink/flickr)

While Robben Island lacks the distinctive architecture and sweeping grand views of Venice, it makes up for it in its singular historical significance. Robben Island is two square miles of flat ground just off the coast from Cape Town, South Africa that housed the prison holding Nelson Mandela, Jacob Zuma (current president of South Africa), and many other opponents of the Apartheid-era South African government.

The entire island is no more than 15 feet above sea level and faces out to the volatile and active South Atlantic Ocean.

Independence Hall

independence-hall Independence Hall is just a few blocks from the Delaware River. (Photo: Peter/flickr)

Independence Hall, where both the Declaration of Independence and the U.S. Constitution were signed, is located in Philadelphia and thankfully isn’t in as much danger as Venice or the Sydney Opera House. But it is just a few blocks from the Delaware River and not more than 40 feet above sea level. As sea levels rise, they also raise the base level for storm surge. All it will take is one good hurricane hitting at just the right angle and time pushing its storm surge up the Delaware River to flood Independence Hall. The higher the base sea level is, the more likely that scenario.

Florida

miami sunset Miami is only about six feet above sea level. (Photo: Bryan Sereny/flickr)

Yup, just about the entire state of Florida stands a real risk of being inundated by the rising seas. Florida is flat and featureless, geographically speaking, rarely rising more than a few stories above sea level. Miami, a city of more than 400,000 people, is just six feet above sea level. Key West streets already get flooded by summer high tides.

On top of the direct dangers poised by the rising seas, Florida also faces the possibility of a creeping flood from below. Florida sits on a bedrock of porous limestone and as sea levels rise, fresh water is displaced by brackish sea water. During big storms, this water can actually bubble up from the ground, flooding areas miles inland.

Tower of London

tower-of-london The Tower of London is in danger from rising seas due to its location. (Photo: Bob Collowân/Wikimedia Commons)

The Tower of London, which is actually a full-size castle, was first built on the banks of the Thames River around 1078 and was meant to both physically and visually dominate the area. Used by British nobility as both home and base of operations, it was contested as a point of power for centuries before falling into use as a prison.

The Tower of London is in danger from rising seas due to its location. The Thames river is protected to some degree by the Thames Barrier, a set of dams running the width of the river that can be raised in the event of a strong storm surge to cut down on flooding. The protection won’t last forever though. The original planners of the barrier didn’t fully plan for the accelerated rise in sea levels that we’re seeing as a result of climate change and the level of protection provided by the Thames Barrier is set to decline after 2030 or so. There is also always the danger of chaos stepping in and slapping you with a dose of badly timed events— in 1997, a dredger crashed into one of the Barrier’s piers and dropped more than 3,000 tons of dug up river bed before sinking. The gates were blocked for nearly a month as workers salvaged the ship and dug up the dumped dirt. Thankfully there was no need to close the gates during the window of downtime, but next time London might not be so lucky.

This story was originally published in March 2014, and has been updated with new information.