JUDY WOODRUFF: The world's oceans and the world's ice are increasingly feeling the effects
of climate change, and the risks of dire consequences are growing.
That's the message of a new report out from the U.N.'s Intergovernmental Panel on Climate
Change.
Scientists say it's virtually certain that the oceans and seas have already absorbed
an enormous amount of excess heat in our climate system, but if current levels of carbon emissions
don't change, the risks for marine life and for people living near the coast will get
significantly worse.
William Brangham is here with more.
It's part of our regular coverage of the Leading Edge of science.
WILLIAM BRANGHAM: Judy, the report is filled with some very specific and very sobering
assessments.
Among them, if greenhouse gas emissions aren't reduced, sea level rise could hit three feet
by the end of the century, driven in large part by the melting of the ice sheets and
glaciers on Greenland and Antarctica.
There are many other impacts detailed in the report as well.
One of the lead authors of this report joins me now.
Michael Oppenheimer is a professor of geosciences and international affairs at the Woodrow Wilson
School at Princeton University.
He authored the chapter on sea level rise.
Professor Oppenheimer, always good to see you here on the "NewsHour."
Let's dive right into the section that you authored.
This prediction of sea level rise, if current trends don't change, seems incredibly stark.
MICHAEL OPPENHEIMER, Professor of Geosciences and International Affairs, Princeton University:
Yes, well, sea level is rising, and it's rising at an accelerating pace.
And the reason for that is -- you said it -- the Greenland and Antarctic ice sheets
are losing ice faster and faster.
They're dumping into the ocean.
And that's a major cause of sea level rise.
And that's also behind -- that, largely, is the human-caused warming of the Earth.
The second thing to be concerned about is that sea level rise is projected to cause
a large change in the frequency of occurrence of extreme water levels at the coasts.
And these are the things that cause big floods.
For instance, when a storm like Hurricane Sandy comes along, and there's a storm surge,
if it's rise riding on top of a higher sea level, it just pushes the water to a higher
level in the places inland, where people live.
And the third thing that we have to know about this problem is that we basically face at
the extremes two types of futures.
The changes can keep accelerating, because, under the business-as-usual scenario, that's
what happens.
Sea level just keeps rising and rising at a faster pace through 2300.
That's the furthest we went out, the year 2300.
An alternative is to start the kind of strong emissions reductions that were agreed to in
the Paris agreement in 2015.
And, in that case, sea -- the rate of acceleration of sea level slows.
Sea level eventually, long, centuries out, stabilizes.
And that means that we buy time.
That would give us a chance to adapt to the problem.
If we don't slow it down, it's going to become unmanageable.
WILLIAM BRANGHAM: I think the report detailed how what we used to consider these once-in-a-century-type
flooding events, by 2050, if we don't make any of the changes you're describing, could
be happening every single year.
I mean, that kind of an impact on coastal communities doesn't strike me that those communities
are prepared for that kind of flooding.
MICHAEL OPPENHEIMER: They're really not prepared.
There are very few places in the world -- the Netherlands is one -- which is prepared for
a higher sea level, up to maybe a couple of meters higher.
But the trouble is that most of the world hasn't paid attention to this problem.
In fact, in most places, they don't cope very well with the current risk.
And you can see that in the United States, where every time there's a big storm that
comes along, there's loss of property, loss of money, and, in many cases, loss of life.
We have to up our game with regard to adaptation, or it's going to get out of control.
And that's much easier to do if we're working in a world where emissions are going down,
rather than a world where emissions are going up.
WILLIAM BRANGHAM: The report also details a lot of the scientific evidence that the
ocean is warming because it is absorbing the heat that we have been building up in our
atmosphere, and that the acidity levels of the ocean are going up.
What does a warming, more acidifying ocean do?
MICHAEL OPPENHEIMER: When the ocean warms, particularly when it's subject to new phenomena,
marine heat waves, you get patches of the ocean that lose their oxygen.
That's because oxygen tends to disappear from warm waters.
It's also because pollution is causing algae blooms.
When those blooms sink in the ocean, they decay.
And decay means basically the organisms or the dead material eats up oxygen.
When oxygen disappears from parts of the ocean, organisms that are supposed to be alive and
that provide us food through fish, for instance, they disappear.
So we're undermining the ability of the ocean to feed the organisms in the ocean and, therefore,
to feed us by warming it and acidifying it at the same time.
WILLIAM BRANGHAM: I'd like you to take off your IPCC hat for a section.
I want to ask a question about political will.
Five days ago, we saw four million people on the streets demanding action.
On Monday at the U.N., we saw world leaders relatively minor commitments to fight climate
change.
Do you think this evidence is going to be enough to move the needle?
MICHAEL OPPENHEIMER: Science is never enough.
Science can set the basis for solving a problem, but it's people that have to decide they want
it solved, and they have to tell their leaders that they want it solved.
That's my personal opinion.
IPCC doesn't criticize or comment on governments.
So it's very encouraging to someone like me, who has worked on this problem for 35 years,
to see the young people in the streets demanding action.
My generation didn't solve the problem.
Now it's going to be on their shoulders.
They know it, and they're angry about it.
And I think that this is going to result in political change, not fast enough, but I think
it's coming.
But a part of the problem I'm really worried about is, you cannot solve the coastal problem
just by reducing emissions.
The federal government doesn't give much, if any, money for planning and adapting, doing
things like building buildings that are on stilts or floodable, building seawalls.
They just don't give much for this kind of thing in advance.
But after a big storm, sure, they come in, they fix up the situation, they pay billions
of dollars.
But it's too late by then.
It would be much cheaper to fix it in advance, before people die, before billions are lost
in property.
WILLIAM BRANGHAM: As always, Michael Oppenheimer, a pleasure to have you on.
MICHAEL OPPENHEIMER: Thanks for having me.