Australia is burning. An area about as large as West Virginia has been blackened by the fires and according to a University of Sydney scientist it's estimated a billion animals have died. The blazes are bigger than the ones that torched California and the Amazon, events that took place on different continents, but are part of the same story: global climate change. It's a story not just of fire but water. Before climate scientists worried about Australia burning, they warned that Venice, Italy, is drowning. Man's most beautiful artifact, built on millions of pylons in the middle of a lagoon, may be vanishing before our eyes. The periodic floods of Venice have become more threatening and more frequent. This past November, a sudden storm surge overwhelmed nearly 90% of the city. Climate scientists say what happened that night exactly two months ago in Venice is a warning to the world of what's to come – and not just in Venice.

Flooding in Venice Eric Kerchner/CBS News

Ever since the fifth century, Venice has depended on the water for survival. This improbable Italian city, knit together between islands, used water as a barrier against invaders to become a jewel of the world. Then came the night of November 12.

Streets ran like rivers, squares became swimming pools, it was Venice's second-highest tide ever recorded, more than six feet above sea level, wind from a storm barreling up the Adriatic Sea accelerated from 6 miles an hour to 70 in less than 15 minutes. When the surge was over, the destruction totaled a billion dollars.

Toto Bergamo Rossi: It's enough. I said to myself the other night, with the water until almost my underpants downstairs. I mean, this is ridiculous. This, we can't be like this.

Toto Bergamo Rossi is known as Venice's unofficial mayor. A descendant of an ancient Venetian family, he is a director of the Venice Heritage Foundation.

Toto Bergamo Rossi: I feel like I'm the doctor of this kind of old patient and I have to do it. I have to check, I have to help

John Dickerson: If Venice is a patient, is it time to call the ambulance?

Toto Bergamo Rossi: Now I think is like, how you call that kind of department (laugh) that they put you the mask and you are in (laugh)

John Dickerson: Oh yeah, the intensive care unit.

Toto Bergamo Rossi: Intensive care (laughs) exactly. Now we are in intensive care. Completely.

Toto Bergamo Rossi

But it wasn't just one flood. For days in November, Venetians woke to the sound of tones warning of more record breaking tides. Venice has always been vulnerable. The city is also slowly sinking, but the water is rising higher and more frequently. Three of the eight highest tides in Venice's recorded history occurred just in November. This is becoming the new normal. And water-logged Venetians wonder how much more this ancient city can take.

Mayor Luigi Brugnaro (Translation): The frequency, it's like an earthquake. When there are too many, then it means something is happening. I see it as an opportunity to wake up the world.

Luigi Brugnaro, a conservative and former businessman, is Venice's elected mayor.

John Dickerson: Are you convinced that the recent water rise, the frequency of the water rise is the results of manmade climate change?

Mayor Luigi Brugnaro (Translation): Yes, of course. Yes, these are the effects of climate change.

Venice Mayor Luigi Brugnaro

These extreme events are damaging many of Venice's masterpieces, like the 900-year-old Basilica of St. Mark, known as the Church of Gold. Its marble floors were swamped on November 12, and downstairs water buried the crypt for only the second time ever. The water receded but left behind salt, which italians call the cancer because it eats away at mosaics and foundations. Pierpaolo Campostrini, who helps manage the basilica, pled for his church and his city.

Pierpaolo Campostrini: I'm emotional. I'm also a bit angry about this.

John Dickerson: Who are you angry at?

Pierpaolo Campostrini: It's the fault of my generation. So I don't want to leave to my children this responsibility. My generation should act.

This past November, Venice nearly lost another of its gems. At La Fenice, where Verdi debuted his operas "La Traviata" and "Rigoletto," November's flood hit days before the season opener. Once the danger was over, Fortunato Ortombina, La Fenice's artistic director, relived the drama of the panic backstage.

Correspondent John Dickerson with Fortunato Ortombina, La Fenice's artistic director

Fortunato Ortombina: Can you imagine this tube with a water? Coming out like a fountain.

Fortunato Ortombina: It was completely under the water.

John Dickerson: And it's never supposed to have any water.

Fortunato Ortombina: No, no, no, no, no. If the water arrives, on the cable, on the line, where you have electricity, it explode. It explode.

Miraculously, it didn't. And with vacuums running around the clock, the water went down so the curtain could go up. The opening scene from Verdi's "Don Carlo?" A prayer for the dead.

Michael Oppenheimer: Venice is facing an existential threat essentially to the city as it has been.

John Dickerson: You say Venice is dying. Those are the stakes for you?

Michael Oppenheimer: Those are the stakes.

Michael Oppenheimer

Michael Oppenheimer is a professor of geosciences at Princeton University. He was a lead author of a landmark report for the United Nations on climate change that found coastal cities are increasingly at risk from sea level rise.

John Dickerson: When people look at Venice and what is happening in Venice, more floods, faster and higher, what message should they take for the rest of the world?

Michael Oppenheimer: The rest of the world should take the message that this is what the situation's gonna look like in many places that they live in. Venice is just, you know, as everybody says, "the canary in the coal mine." It's happening there now.

Climate change, Oppenheimer says, is the major reason we'll see more floods for the ages across the globe, like the one that hit Venice two months ago.

Michael Oppenheimer: Sea level is rising almost everywhere on Earth. Not only is sea level rising the rise is accelerating. It's happening faster and faster.

John Dickerson: How much faster has that pace quickened?

Michael Oppenheimer: So by the year 2050, which is only 30 years into the future, many places around the world, including in the U.S., are gonna experience their historical once in a hundred year flood level once a year or more frequently. Let me repeat that. An event that used to cause severe flooding once a century, we're gonna get that same water level once a year.

John Dickerson: And what cities are we talking about?

Michael Oppenheimer: Places like Los Angeles, San Diego, Key West, Miami, Jacksonville, Savannah, Honolulu.

Eric Kerchner/CBS News

But at least there is a plan to defend Venice. We headed out to one of the three inlets where the tides from the Adriatic Sea flow into the lagoon that surrounds the city. This is where Venetians hope that a controversial project called Moses will part the waters. More than 30 years in the making, Moses is supposed to deploy 78 retractable gates to block exceptional high tides, as this animation illustrates. Construction finally began in 2003 but corruption scandals and engineering challenges have delayed moses years past its due date.

John Dickerson: After all the tests are done, when are you saying that Moses will be ready?

Alessandro Soru: It's now planned for the end of 2021.

In a tunnel 60 feet below sea level, we met Alessandro Soru, the project's lead engineer.

John Dickerson: So how many days a year was it planned that Moses would be used?

Alessandro Soru: Say an average of 10 days a year.

But the fear is if the Adriatic continues to rise past projections, the Moses gates may have to be raised nearly every day by the middle of this century. It was not designed for that kind of wear and tear.

The worst flood in Venice's history happened in 1966. It was only a few inches higher than this past November's. Back in '66, experts said the flood was a once-in-800 year event. Nonetheless, thousands of Venetians left for good.

Shaul Bassi: It really was the major historic turning point in the recent history of the city. And we thought that something like that would not happen again.

Shaul Bassi is a product of that flood. A professor of English literature at Venice's Ca'Foscari University, his parents met when his mother went to Venice to help the flood victims. They stayed, but how many will now that the seasonal high tides, known as acqua altas, are getting worse.

Eric Kerchner/CBS News

John Dickerson: Explain how it was different this time from previous acqua altas…

Shaul Bassi: So I think that people now feels far more vulnerable. We're hearing the sirens now (SIRENS IN BACKGROUND). Acqua alta's coming back. You see? This is what happened. It's happening every day now. This never happened like that. You know, it happens one, two, three days. Now, it's like, over a week that every day we have that. This is new.

John Dickerson: When you hear the sirens, does that take you back?

Shaul Bassi: So I (pointing), you know, now it really makes me feel very nervous.

During our eight days in Venice, we found the city on edge because the water keeps defeating the accommodations residents have already made to it.

Shaul Bassi: The real, real threat, as far as I'm concerned, is that it may actually push even more people away and will leave the city as a kind of ghost town, as a beautiful empty museum.

The ground floors in this stooped and shrinking city have already been abandoned. Life is lived on the first story and above. Artisans like Saverio Pastor, one of the last who patiently crafts oar locks for the city's gondolas, are becoming scarce. While residents weigh moving out, the tourists keep marching in, donning neon booties and learning to walk on water or in single file on the hastily assembled footbridges that lace through what may be a doomed city.

To give venice a future, its mayor wants to turn the city into a world laboratory to combat climate change.

Mayor Luigi Brugnaro (Translation): Why don't we do it here? Let's do it here, let's study it here. Let's study the water, let's study the pollution, the rising waters, the temperature. It could be an example of great mobilization at a world level.

John Dickerson: Is the message to the rest of the world, if you don't save Venice, it will happen to you next?

Mayor Luigi Brugnaro (Translation): I don't want to worry anybody, but I think that I'd like a different message. Let's save Venice to save the world.

Venice has survived before. Every November, Venetians flock to the Santa Maria della Salute church, which was built to commemorate the end of the 17th century plague that killed 50,000 citizens. This year's ceremony, in the wake of the flood, had a special resonance.

Shaul Bassi: The festival is a festival about survival.



John Dickerson: Was it more well-attended this year than it woulda been in the past?

Shaul Bassi: Absolutely. I think that it was more heartfelt. I think a lot of people this time felt, you know, 'This might not be there forever.' I think this is what has perhaps changed, that a lot of us are feeling, 'Well, we cannot take this for granted.'

What would be lost is a city where so much of the art interprets the natural beauty of light that arrives twice a day, once from the sun and once as it is reflected back off the water, but Venice is no longer just something beautiful to look at. Its fragility is a warning to the rest of the planet that this ancient city is under pressures from forces it cannot control. Venice is not alone. In a world of warming temperatures and sea level rise, no place is an island.

Produced by Draggan Mihailovich. Associate producer, Jacqueline Williams. Field Producer, Sabina Castelfranco. Broadcast associate, Claire Fahy. Edited by Warren Lustig.