>> Earth's polar regions are

sensitive enough that a

difference of 1 or 2 degrees

in temperature can thaw

a world of ice.

Polar scientist Marco Tedesco of

Columbia University's

Earth Institute has been

studying these warmer winters

that affect our poles and our

planet.

This segment is part of our

ongoing series of reports,

"Peril and Promise: The

Challenge of Climate Change."

Thanks for joining me.

>> Thank you.

>> So, you guys put out a report

card.

What's in an Arctic Report Card?

>> Well, the Arctic Report Card

is something sponsored by NOAA,

which groups many scientists --

this year, 61 scientists -- to

put out what is the state of the

arctic in a very fast and quick

way, right after when the data

comes out fresh from the

sensors, so that we can have a

better picture of what the state

of the arctic is, what's

happening, and if things are

changing.

>> So, what are the grades of

the arctic, and what's been

happening over time?

>> Well, the arctic has been

warming, first of all,

at a very fast pace.

Mostly twice the rate of the

rest of the planet.

For 2016, for example, the

arctic, just the land over the

arctic, was up to about 3.5

degrees Celsius -- about 6.3

degrees Fahrenheit --

warmer than the average.

And the overall arctic was about

2 degrees Celsius -- about 4,

4.5 Fahrenheit -- warmer than

the rest of the world.

>> So, is it happening at the

pole more so

than in the rest of the planet?

>> Well, when the rest of the

planet warms up, there is

something we call

arctic amplification.

The arctic amplification is

really the mechanism through

which the arctic warms much

faster than the rest

of the world.

One example, there are all these

feedback mechanisms -- so,

mechanism that amplifies the

effect of a warming world.

For example, this appearance of

sea ice.

You replace a very bright

surface that reflects all of sun

radiation and keeps the planet

cool with the dark ocean

that absorbs a lot of solar

radiation, it keeps warming more

and more the arctic.

This, for example, and other

aspects are all mechanisms.

They're amplifying the warming

of the arctic, and this is what

happens.

>> So, is it a bit of --

I hate to mix snow and ice here,

but -- a snowball effect, where

the more ocean you get, the more

heat it absorbs, the faster it

melts, the more ocean you get --

>> Correct. Correct.

The snowball effect.

Sometimes I'll describe it like

a train running downhill,

for example, right.

So if you put the temperature as

your coal in the furnace, your

train goes faster and faster if

you put more coal.

But if your train is running

downhill, like the amplifying

mechanism on your speed, then

even if you don't start putting

more coal, the train will keep

accelerating farther and

farther.

And so that's what happens.

You put more coal, we're going

downhill, and everything happens

much faster.

>> So, let's talk a little bit

about, what are the actual

impacts on the surface?

So, places like Greenland.

They're not as green as they

once were.

Or maybe you're seeing more

green now than you used to see.

>> Well, we don't see a lot of

green, but we see less ice.

And also we see more bare ice

exposed.

You know, snow is one thing.

Pure snow, bright snow, it

really reflects a lot of solar

radiation.

The ice which is below the

snowpack, is really what really

puts water into the ocean,

that contributes to sea-level

rise, because this ice has been

locked for a very long time on

the ice sheet and is not part of

the water cycle.

And so when we expose this

bare ice, it's very dark, it

contains dark material, and so

it absorbs the sunlight much

stronger, and it melts much

faster.

And so we are starting to remove

this ice that was locked for

tens of thousands of years and

putting it into the ocean, which

is directly contributing to the

sea-level rise.

>> And that sea-level rise can

be felt globally.

>> It can be felt globally, yes.

So, everything you put into the

ocean will be redistributed, but

overall the impact that this

might have is both local in

terms of salinity, ecosystems,

fishery, but also global in

terms, of course, of sea-level

rise in coastal regions.

>> So, if you put a cube of ice

in a glass of water, it doesn't

necessarily change, but it does

start to expand, and over time,

when that melts, you get a lift.

>> Right.

So, the reality is that the ice

is not sitting in the water.

It's sitting on land.

So everything that we remove

from land to the ocean, that

actually is increasing our

glass of water.

>> So that's the equivalent of

adding more and more ice cubes

in, right?

>> It's the equivalent of adding

more and more ice cubes.

There are shelves, of course,

ice is sitting into the water.

That does not add up.

But when those are removed, that

is really the unplugging the

cork of your champagne bottle,

and then all the ice behind can

start flowing much faster, and

this increases sea-level rise.

>> So, as these

changes are able to be

measured...

>> Mm-hmm.

>> There are different

scientists that say we're at a

tipping point, we're nearing a

tipping point, we're past a

tipping point.

Can this be slowed?

>> Well, it can be slowed, but

we don't know how fast it can be

slowed.

And there are mechanisms that

can counter-effect the

acceleration that we're seeing.

Namely, putting more snow --

or cooling down the planet.

This is really the recipe.

There's no big other issue or

big other thought to make.

And you can do this by reducing,

of course, the CO2 emission.

So, the thing that is very

important to think of is,

the time it takes to destroy or

to remove the ice from the ice

sheet is much faster than the

time it will take to build an

ice sheet.

You can really see this like

building slowly something that

takes a long time to

consolidate and take shape,

and then suddenly you take away

the base of the structure,

everything collapses.

To build it back still takes the

same time, which is a long time,

and it's much longer than

destroying it.

>> So, how do you measure the

warming that's actually

happening?

>> Well, the warming is measured

through a series of things.

Satellites are observing the

surface, the ocean and land

surfaces, through a network of

sensors on land, through models

that try to replicate what

happened in the past and is

happening in the present to

project what will happen in the

future.

For example, satellites, they've

been used to measure the mass of

Greenland -- how much mass

Greenland is losing.

They've been measuring, too --

they used to measure also how

much snow is falling here, and

how much melt is occurring.

We have all this beautiful set

of sensors, which we didn't have

until 10, 12 years ago,

together with the advances of

supercomputing and the

possibility of exploring this

data, and a new generation of

scientists who's really focusing

their effort on understanding

better these processes through

these great data sets.

And so we can have a better

picture now than we had even

just 10, 12 years ago.

And this is somehow much better

for us, but it's also more

frustrating, because the more we

know, the more we think there's

an action that needs to be

taken.

>> Is there any question that

humans are contributing to this?

>> Well, not on my point of

view, and not to the opinion of

the IPCC.

I think being skeptical is a

good thing.

I do agree with people who say

that being scientists means also

being skeptical.

This doesn't also mean that you

need to start attacking a lot of

things that are easy to defend

when you don't have the time to

do it, or when you can do it in

a fair way.

So, to me, there's really a

little point to discuss about

this.

>> Well, one of the things that

even the head of the EPA says is

it's really hard to measure the

amount that humans contribute to

all of this.

But given all of the work you're

doing, all of your peers are

doing...

you're fairly certain that this

is warming that is caused by

humans, and you can see the

impact on the arctic?

>> Right.

I do agree, it's very hard.

But I do think, also, that the

scientific community is doing an

excellent job.

Being hard doesn't mean it's

wrong.

I do think that there's more

need to better understand and

refine the projections

in which way.

We want to know, for example,

whether there will be a problem

for Battery Park in 20 or 40

years, if there is a storm surge

coming with an increase in

sea-level rise, instead of being

out one week, we'll be out maybe

a month, or a blackout in the

subway like happened with Sandy.

So in this regard, yes, we need

to refine better, but we need to

do it because we need to provide

our expertise and service to the

public by refining our

projections, and work with

policy makers to basically give

back what we take from the

public, which is the federal

taxes used for the

good of the public.

>> All right.

Marco Tedesco, professor at

Lamont-Doherty Earth Observatory

at Columbia University.

Thanks for joining us.

>> Thank you very much.