NOVA

It's a city's worst nightmare.

Megastorm Sandy delivers a wall of water 14 feet high...

There was no way to stop it.

...plowing into New York.

You needed Superman, I guess.

And across the region, crucial services collapse.

This is Manhattan, and it was just chaos.

Miles of coastline are devastated.

DAN MUNDY, SR: Whatever anybody could do,

it was not enough.

And who's to say it ain't going to happen again?

But there is little doubt it will.

The planet is heating up.

Glaciers are melting.

Sea level is rising.

Should warm ocean currents reach these glaciers,

all hell could break loose.

How do we protect ourselves?

Can we wall off our cities from the sea?

Are some places destined to disappear?

Florida is doomed.

In the wake of Sandy,

how will we respond?

This is screaming at us that we need to be better prepared.

"Megastorm Aftermath," right now on NOVA.

Major funding for NOVA is provided by the following...

Supporting NOVA and promoting public understanding of science.

And the Corporation for Public Broadcasting.

And by:

And Millicent Bell through:

Additional funding from:

Major funding for "Megastorm Aftermath" is provided by:

Expanding opportunities in America's cities.

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Furthering the values that contribute to a healthy planet.

New Yorkers pride themselves on being tough...

We'll ride it out like we ride all of them out, you know?

...resilient, nonplussed,

and maybe a little cocky in the face of adversity.

It's raining here,

but, um, you know, whatever, it's a little rain.

What are you going to do?

But on October 29, 2012...

This is a record surge of water rushing over the edge

of Lower Manhattan.

...they, and their city, met their match.

My God, it's washing everything away!

That was the day megastorm Sandy came rolling into town.

The storm is on top of us right now.

It was the biggest, most devastating storm

to hit the city in recorded history.

Strong winds pushed a huge wall of ocean water

14 feet higher than sea level, onto the coast,

covering 51 square miles of the city.

70,000 homes and apartments were damaged.

An entire neighborhood burned to the ground.

Utilities failed in spectacular, massive fashion.

And 43 people died here, most of them drowned.

Sandy brought mighty Gotham and much of New Jersey

to their knees.

As soon as the waters recede, unsettling questions

begin to roll in.

Was Sandy a freak event, or a window into our future?

We live in a new era.

Greenhouse gases like carbon dioxide

generated by burning fossil fuels are building up

in our atmosphere, insulating our planet,

holding in more of the sun's heat

and driving the temperature up.

The Earth's climate is changing.

No one knows exactly how that will affect our weather

day to day.

But there's one thing scientists agree on:

as the Earth and its oceans heat up,

warm water takes up more volume than cold.

At the same time, glaciers are melting.

The result-- sea level around the world is rising.

And that means as the storms come...

coastal cities are more and more at risk.

Climate change will raise the sea level,

and sea level will contribute to the power of flooding.

It's not only New York and New Jersey

that are in the crosshairs, but Miami, New Orleans, Charleston.

As our sea level continues to rise,

it won't take a Hurricane Andrew or Katrina-size storm

to create flooding hazards along our coastline.

Thousands of miles of coastline all around the world--

China, India, Japan.

We live increasingly in coastal areas.

This is screaming at us

that we need to be better prepared.

But what can coastal cities do

to prepare and protect themselves?

Can we engineer a solution

and wall off our cities from the sea?

Or are some areas just too hard to protect,

and, eventually, should they be abandoned?

We have to start to retreat

from the most exposed waterfront.

As New Yorkers, we cannot

and we will not abandon our waterfront.

It is one of our greatest assets.

Or is there another way?

A way to embrace nature's defenses and the water,

even as we try to keep it at bay?

Sandy should demand a national response.

There but for the grace of God, it could have been Boston,

it could have been Seattle.

It could happen to Houston.

How are we as a nation prepared for dealing

with these kinds of risks?

And reality is we're not near as prepared as we need to be.

As Sandy approached, Dan Mundy knew his home was at risk.

The retired firefighter lives in one

of the most flood-prone neighborhoods of New York City--

Broad Channel.

It's a sliver of an island in the middle of Jamaica Bay,

on the southern end of Queens.

Elevation above sea level: about four feet.

It's very unique what we have here.

It's very different.

People that don't know and come and visit and see it,

they say, "Wow! This is beautiful.

Look at your views."

Well aware that his home was in harm's way,

Dan Mundy built his own private seawall around it.

You can see my bulkhead out there.

There's 250 tons of stone.

But the fortress couldn't hold back Sandy's storm surge.

You see how high it is and how big it is.

Well, Sandy come over the top of it.

It was just unreal.

This storm, it just went beyond.

Whatever anybody could do, it was not enough.

And, you know, who's to say it ain't going to happen again?

That's the question haunting thousands

whose homes were damaged or destroyed by the sea.

Sandy's waves tore through the Rockaways,

about five feet above sea level.

The Red Hook section of Brooklyn: eight feet.

Staten Island: four feet above sea level.

Lower Manhattan: about eight feet at the Battery.

In New Jersey, Sandy caused flooding

from Hoboken to Atlantic City.

Around the region and around the world,

the question is not if it will happen again,

but when, and how often?

We know very well a mean trend where things go.

The sea level rise will not go down.

We know that for sure.

What scientists don't know for sure

is how fast it will rise.

Over the past century, sea level around New York

is up about a foot, partly because of subsiding land.

But how much will it rise in the next hundred years?

That may depend on what happens here...

in Greenland...

where vast masses of ice are flowing from land to ocean,

raising the sea level.

David Holland is trying to crack the sea level mystery.

That's what's brought him here on a hazardous voyage

though the iceberg-cluttered waters of Jakobshavn Fjord

in Greenland.

They say the iceberg that sank the Titanic

came from this breathtaking and extremely dangerous place.

These things roll.

And if it rolls, it will take the ship with it.

Holland is a mathematician,

and he's here because he doesn't have much faith in the numbers.

I would state that at this moment

we cannot project future sea level mathematically.

We have to be honest with ourselves.

We have incomplete knowledge at the moment and incomplete data.

Some of the data we do have is disturbing.

An enormous reservoir of fresh water is locked up

in the glaciers here, at least for now.

If you melted all of Greenland, then local sea level

around the planet would rise just over 20 feet.

20 feet would submerge more than a third of the city of New York.

But no one is predicting that this will happen anytime soon.

The Greenland glaciers have been slowly melting

for thousands of years, since the end of the last Ice Age.

But today, with the planet heating up faster,

there are ominous signs that the movement of ice

from land to sea might be speeding up.

David Holland believes

the reason lies not in the warming air,

but in the water.

As a glacier slides off the land,

its underside comes into contact with the seawater.

In 1997, the ocean currents changed abruptly,

and the water here got warmer by nearly three degrees Fahrenheit.

Soon the glacier started melting much faster.

During the 20th century, it retreated eight miles.

But in just the first decade of the 21st century,

it receded another nine miles.

David Holland is trying to solve the mystery

of why this happened, and if it could happen again.

The main thing we're trying to study is

how do warm currents approach ice sheets?