IRA FLATOW: This is Science Friday. I’m Ira Flatow. A bit later in the hour, a look at why we hitch.

But first, with heat waves and wildfires in the West, an active hurricane season in the Gulf, our attention has been turned away from other dramatic and life changing evidence of our climate crisis, the rapid melting of the ice at the Poles, with sea ice shrinking in the Arctic and the ice sheets covering Antarctica cracking and slipping into the southern seas. But scientists have been paying attention, using satellite data, radar readings, and a massive computer simulation. And the projections are not good. Once the glaciers melt, they don’t refreeze the same way, even if temperatures drop again. And that spells bad news for sea level rise.

That study was recently published in the journal Nature. Joining me is one of the authors, Anders Levermann, Professor for the Dynamics of the Climate System. He’s based at the Potsdam Institute for Climate Impact Research in Potsdam, Germany. Welcome back to Science Friday.

ANDERS LEVERMANN: Hi. How are you?

IRA FLATOW: Fine, Thank you. Your research shows something I think a lot of us would be surprised to learn. And that is what gravity has to do with ice melting. Can you explain that for us?

ANDERS LEVERMANN: Well, ice sheets form by snow that falls onto land and then slowly builds up to be an ice sheet. But if you stack up ice up to a certain height, like in Antarctica, you have almost four kilometers, that’s 4,000 meters of ice sheet, up into the sky, then this is really pulled down by gravity. And it’s kind of squeezed on its own weight out into the ocean. That’s why there is a balance between the snowfall and the flow into the ocean and the ice sheets on gravity.

IRA FLATOW: So how does that influence how the ice is melting in Antarctica?

ANDERS LEVERMANN: In this case, actually not really melting, because– we have a lot of melting in Greenland and elsewhere on the planet. But Antarctica is around the South Pole. And it’s terribly cold there.

So most of the ice that is lost is flowing into the ocean. It’s not really melting. It’s flowing into the ocean. And the ice flows faster when it gets warmer. And that’s the problem.

IRA FLATOW: So when it reaches the coastline, it’s calving off on those giant icebergs and things like that?

ANDERS LEVERMANN: Exactly. And partially melted, too, of course, when it reaches the ocean.

IRA FLATOW: So the takeaway message here then is it’s not good. I mean, what does your model say? Even if we keep to the 2 degrees Celsius mentioned in the Paris Agreement?

ANDERS LEVERMANN: Yes. We find that on really long timescales, we can compute how much ice will actually survive at different levels of warming. We found that the ice sheet becomes more and more sensitive to warming. Up to 2 degrees Celsius of warming, which is the Paris climate agreement, we lose about five feet of sea level equivalent, sea level rise equivalent of ice per degree of warming.

But beyond that, after the two degrees target is reached, we even lose seven feet per degree of warming, up to 6 degrees, which we will reach without any climate protection within the next 100 years roughly. And after that, after six degrees, is really a terrible amount of warming, we would have much more problems than just sea level rise by then, but after that it gets even more dramatic. Because we get 30 feet for every degree of warming.

IRA FLATOW: So it’s not a linear rise in sea level?

ANDERS LEVERMANN: No. It’s not. I mean, like most things in nature, things are not really linear. And in Antarctica, we have a number of feedbacks that play a role whenever you have an ice sheet that’s actually grounded under the sea level. So it’s grounded on the seafloor.

But it’s so thick that it reaches out into the air. And if you have this kind of situation and then the seafloor is falling when you go inland, it’s falling down, then you have a situation which is prone to a so-called marine ice sheet instability. And once you have melted a little bit away of the ice on the fringes and the coast, then all of a sudden you don’t have to melt anymore. You’re just losing the ice to an instability, meaning [INAUDIBLE] feedback that pushes all the ice into the ocean until the basin is empty.

IRA FLATOW: Give me an idea of what five meters means to people who live around the world.

ANDERS LEVERMANN: Yes. Five meters, or roughly 15 feet, is what we get eventually at two degrees of warmth. And five meters of sea level rise really puts a number of big cities at risk around the world. It’s relevant for New York, Shanghai, Calcutta.

Hamburg, for that matter, which is a relatively small city. But in general, we care about it. Because it had its 750 year anniversary when I was a kid. And for the next 750 years, I don’t see it. I don’t see that we’ll live in Hamburg in 750 years.

IRA FLATOW: And that’s just with the five meter rise. But it could be even worser or deeper than that?

ANDERS LEVERMANN: Well, what people don’t realize is that if we continue to emit carbon into the atmosphere, this carbon stays there practically forever. It’s not like if we reduce the carbon emissions, then we reduce the warming. That’s not the case.

No, we just reduce the speed, the rate with which it’s warming. If we want to stop the temperature increase of the planet, the rise of the temperature, we will have to go to zero emissions. And we are far from that. It’s only going up almost every year with the emissions.

So even if these temperature limits of 2 degrees, 3 degrees, and so on and so forth seem very far away, they will come if we don’t stop emitting carbon. We’ve found enough coal in the ground to make it as hot as it was when the coal was actually built, when the dinosaurs were on the planet. And there was, like, 15 degrees Celsius warmer than today. And with 15 degrees warmer temperatures, which we will reach if we don’t stop emitting carbon, we’ll have an ice free planet. And that means 60 meters of sea level rise worldwide, or even more.

IRA FLATOW: How many meters was that?

ANDERS LEVERMANN: 60, that’s 180 feet. That’s an incredible amount. And it won’t happen overnight. Don’t worry. It will take a long, long time.

But that’s the amount of ice that we have on the planet, mainly in Antarctica. And that’s what we’ll get if we don’t stop emitting carbon.

IRA FLATOW: I’m trying to be hopeful about this. But you don’t make it sound very hopeful.

ANDERS LEVERMANN: Well, sea level rise is not really a threat to lives if you take it seriously. If you have administrations take it serious [INAUDIBLE] you can always abandon the coasts, right, or you can protect against a certain amount of sea level [INAUDIBLE] some regions. But if you take it seriously, it’s not really a threat to life. But it’s a threat to what we built near the coasts.

And that sounds less dramatic in a sense. But it’s the cultural heritage that we built there. We built it in New Orleans. We built it in New York. We built it in Shanghai, Calcutta, Hong Kong, Tokyo. And that’s what we’re going to lose if we don’t stop emitting carbon.

IRA FLATOW: The United States is not taking it very seriously in terms of looking toward the future and building or cutting down on carbon emissions. But are there other countries that, say, hey, we’d better start doing something. If not talking about reducing carbon emissions, at least moving away from the coast and anticipating exactly the kind of sea rise you’re talking about?

ANDERS LEVERMANN: Most coastal cities, or like the countries that really have only coasts, the island states, they take it very seriously. And they know– for example, for the Pacific island states, a lot of them, it’s an existential threat. And one has already been abandoned, actually.

No. It’s generally not, let’s say, a problem that coastal protection agencies take it seriously, because they see the sea level rising. The problem is that we really have to get to zero emissions. And that sounds like a dramatic, almost radical political request or demand.

But it’s not. It’s a physical reality. And it’s quite simple. But it’s actually also good for the economy.

That sounds [INAUDIBLE], I know. But doing something less, like reducing emissions, is always– it sounds in the ears of most people in the industry is if we want to not have growth, not economic prosperity and so on. But getting to zero emissions means we have to do something completely different.

And completely is a different issue. Right? You can make money off of that. I don’t want to say let’s all make money off of protecting the climate.

We have to protect the climate because we really need to. But you know, conveying it like this might be sometimes helpful. Because we really have to get the technologies that get us to zero emissions, not just less.

IRA FLATOW: We’re in the middle of a political season here, of course, in the United States. And one of the ways that people talk about the Green New Deal, or Joe Biden’s plan, as he spoke about it during the debate this week, was doing this would create new jobs.

ANDERS LEVERMANN: That’s exactly what it is. It’s not bad for the economy to save the planet. You know, we’re giving a gift to industry. Because we are telling you what’s going to happen in 30 years.

Now, if you can’t make money out of this information, then you’re kind of not a very good business man. In the European Union, what has been done is we’ve given carbon a price. And that’s how you can create a competitive advantage by carbon emission reduction. And that’s exactly the path forward.

Now we have the EU commission president has just come up with a stronger plan, and it is not finished yet. But if it works out, then a huge market on the planet will go carbon free in a lot of sectors, economic sectors. And that’ll have, obviously, some influence on the other regions.

IRA FLATOW: And are you hopeful that we can do any of this? Give me a scenario, what you would view as a scenario.

ANDERS LEVERMANN: Yeah. There are a number of possible scenarios. China has a huge climate problem. They have a huge pollution problem which is a different one from the climate problem, right, because CO2 is a molecule and you don’t see it. What makes the air dirty is pollution, meaning aerosols.

But they come together in China. Because it’s a lot from cars and a lot from coal power plants. So I think that China has good reason to go ahead and then go for renewable energies in the future. But recently, Europe has really taken a lead again. They haven’t for a while, but now they seem to be taking the lead again.

And if one of these big centers, economic centers, North America, Asia, or Europe, is flipping into carbon neutrality, then this really sends a strong signal to the others. Simply because they will only buy stuff that’s carbon neutral. I don’t want to sound naive, but we are on the path.

Germany is crazy for cars. We’re going electric at the moment. And it’s going so rapidly that we have to get the cars from outside, Tesla, and so on, and so forth. It’s amazing. Small revolutions are taking place that are not so small anymore.

IRA FLATOW: Well, I’m going to leave it on that hopeful note. We’ve run out of time. I want to thank you for taking time to speak with us today.

ANDERS LEVERMANN: Yeah, thank you very much, Anders Levermann is a Professor for the Dynamics of Climate System at the Potsdam Institute for Climate Impact Research in Potsdam, Germany.

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