GEOFF BENNETT: Welcome to the "NewsHour."

There's alarming new evidence out today showing once again the dramatic impact of climate change.

AMNA NAWAZ: A new study shows that the massive ice sheets at the top and bottom of our planet are shrinking much faster than previously thought.

William Brangham has the latest on what this means for coastal communities around the world.

WILLIAM BRANGHAM: This international study, which compiled satellite measurements over time, depict what one researcher described as a -- quote -- "devastating trajectory."

In the early to mid 1990s, the ice sheets on Greenland and Antarctica were losing on average about 116 billion tons of ice per year.

But, in recent years, that annual loss has more than tripled to 410 billion tons of ice.

As all that ice ends up in the oceans, it's driving sea level rise to an even greater extent.

For more on the implications of this study, we're joined by Twila Moon.

She's the deputy lead scientist at the U.S. National Snow and Ice Data Center.

She was not involved in this most recent study.

Twila Moon, great to have you on the "NewsHour."

You are the researcher that I quoted there is describing this as a -- as a devastating trajectory.

Can you explain why it feels that way to you?

TWILA MOON, Deputy Lead Scientist, U.S. National Snow and Ice Data Center: This is something where, as we're losing ice around the world, the biggest impacts are felt by those people who are actually far from this ice and living in coastal regions in North America, Asia, Africa, all around the world.

And so seeing this continued rise in ice loss is really not good news for dealing with sea level rise.

But I do want to be clear that this is not an inevitable trajectory either.

WILLIAM BRANGHAM: We're talking about ice that used to live up on land now melting, disappearing and ending up in the oceans and driving up sea levels.

Sometimes, I think the numbers here, when we talk about billions of tons, it's hard for people to fathom what we're talking about.

What are the literal downstream consequences for communities all over the world?

TWILA MOON: Yes, I understand how the numbers can seem hard to deal with.

It's important to remember the Greenland ice sheet covers the world's largest island.

Antarctic ice covers a continent.

So these are very vast areas that are hard for us to imagine.

And as we're losing ice from these areas, what we see arising at our coasts are things like coastal erosion, where we're losing land.

We might have ocean water inundating our freshwater resources or causing problems with water and sewer systems.

Or we might see flooding in areas that have never experienced it before, even further inland from the coast, and also areas that do experience flooding having that occur more and more often.

So these are impacts that we feel around the world and those -- for those of us who have felt very far from ice.

WILLIAM BRANGHAM: You were saying that this is not baked in, that we can act on this.

But there is an enormous amount of carbon that we have already put up in the atmosphere.

I mean, even if we stopped today emitting carbon 100 percent, wouldn't there still be some of this pollution and warming that is baked in?

TWILA MOON: Yes, that's correct.

Unfortunately, we have already put a lot of polluting gases into the atmosphere.

So, we can expect sea levels to rise over the next 2030s, 2040s, and that that amount of sea level rise has been baked in, due to our past actions.

But it's very important to understand that sea level rise after that time period is very highly dependent on what human actions we take, what society does to address climate change.

And, in those pathways, the kind of experiences that our children will have and our grandchildren will have is deeply affected by the human actions that we are taking now and over this decade.

WILLIAM BRANGHAM: I know you're not a political scientist, but we just saw another U.N. climate summit come and go with barely any commitment on global action.

Here in the U.S., we're seeing leaders of the GOP trying to neuter the fledgling efforts of the Biden administration to address climate change.

Is it frustrating to you that the evidence of this threat keeps growing, but our appetite to act on that evidence does not?

TWILA MOON: It is frustrating that we're not taking stronger and more immediate actions in many cases.

But I think it's important to still remember that we have made progress from where we were, for example, a decade ago, and that starting progress in one location can pass to another, and we can really create sort of social societal tipping points in a good way.

And so I think that we have to remember there's no expiration climate action.

Every tenth of a degree that we prevent warming is worthwhile and will benefit us.

And we can continue to strengthen our actions.

WILLIAM BRANGHAM: Twila Moon of the National Snow and Ice Data Center, thank you so much for being here.

TWILA MOON: Thank you.