New study outlines grim future for hundreds of thousands of glaciers

Amna Nawaz:

The last eight years have been the hottest recorded in human history. That's according to the European Union's Copernicus Climate Change Service.

And with planet-warming emissions on the rise, scientists worry about melting glaciers and the onslaught of repercussions. A new study published in "The Journal of Science" looks at the future of hundreds of thousands of glaciers, and what we can expect.

To explain the findings and what they mean for the planet. I'm joined by David Rounce, assistant professor of civil and environmental engineering for Carnegie Mellon University in Pittsburgh.

Professor, welcome, and thanks for joining us.

Your study looks at the world's more than 214,000 glaciers. You looked at what happens even if the world manages to meet what is its most ambitious, global warming goal, right, just a 1.5-degree Celsius increase.

What did your study find happens to those glaciers if we can do that?

David Rounce, Carnegie Mellon University:

We found that if we limit the temperature increase relative to pre-industrial levels to a degree-and-a-half Celsius, that will lose approximately a quarter of the glaciers by mass.

The glaciers' contributions to sea level rise will be approximately 90 millimeters. And we will lose about 50 percent of the glaciers by number.

Amna Nawaz:

What's the timeline for that? When do you expect that to happen by?

David Rounce:

Over the next century.

So, we modelled from 2015 to 2100 for various temperature change scenarios.

Amna Nawaz:

Even with that very conservative modeling estimate, you had nearly half of all those glaciers, over 100,000 of them, you said, would disappear by the end of the century.

What would that mean for sea level rise, for example?

David Rounce:

So most of the glaciers that will be lost completely are smaller.

So, out of those 215,000 glaciers, the majority of the glaciers are very small. They're still important for water resources, for culture, spirituality, especially for high mountain communities. But when we think about sea level rise, it's really the largest glacierized regions that are the most important, and there will be ice remaining by the end of the century in those different regions.

Amna Nawaz:

You mentioned the importance, especially when it comes to water supply.

Explain that to us a little bit. I don't know that most people know about that. How important are those glaciers to communities around the world?

David Rounce:

So these glaciers are located in the high mountain regions.

And they act as a reservoir of freshwater. These are in areas such as Central Europe, High Mountain in Asia, Alaska, Western Canada, where there are also large populations located nearby. In high mountain Asia alone, there are over a billion people who rely on these freshwater resources from the glaciers.

And so any changes to the glacier run-off that's available downstream means that those communities need to seek freshwater resources elsewhere, either from groundwater, or they would need to build reservoirs in order to have a similar capacity as to what's provided by the glaciers right now.

Amna Nawaz:

How much of this is inevitable? In other words, in your modeling, I mean, are there — are there actions that you find in your studies that we could or should be taking that would help to slow this down or stop it or reverse it?

Or is this a matter of when, rather than if?

David Rounce:

That's a great question.

And that's one of the things we tried to focus on. As I mentioned, right now, the temperature change increase, based off of current pledges, is estimated to be around 2.7 degrees. So there's a lot that we can do to reduce our carbon emissions and bring that temperature change increase down to a degree-and-a-half.

And, if we do that, we can save about 20 percent of the glaciers by number, and we can save about 8 percent of the glaciers by mass, and we reduce the glaciers' contributions and sea level rise by about 25 millimeters. So we can really have a big impact if we're able to reduce the temperature increase in the future.

And that's something that we should be hopeful about. However, there is the inevitable cause of this glacier mass loss, that glaciers are responding to changes in temperature that have occurred over the last several decades. The response times of glaciers can be very long. And so, even if we were to stop the temperature increase right now, we still have a mountain of committed mass loss that's going to occur regardless.

Amna Nawaz:

Professor, I know you study this. And we're talking a lot about percentages and mass and so on.

But if you could just put it into context for us, when you're talking about a loss on this scale that seems very close to inevitable, how devastating is that for the planet?

David Rounce:

It is devastating. We really focused a lot on trying to understand the differences in these temperature change scenarios.

But one of the things that we found, for example, is that, between a degree-and-a-half, two degrees and three degrees, a lot of regions around the world are very sensitive to changes, such that, with three degrees in the contiguous United States and Western Canada and Central Europe, those regions will experience near complete deglaciation, meaning all of the glaciers will be lost in those regions, while, if we limit the temperature increase to two degrees or a degree-and-a-half, we will at least preserve some of the ice in those regions.

Amna Nawaz:

Professor David Rounce from Carnegie Mellon University in Pittsburgh joining us tonight, thank you for your time.

David Rounce:

Thanks for having me.