Full Transcript

Steve Nerem: You’re heading up towards, you know, that meter type sea level change, which, you know, in the back of my head, I have always carried a meter as kind of the breaking point between sea-level change that’s a nuisance but that we can probably deal with and sea level change that becomes catastrophic where, you know, you have to abandon some cities and things like that.

Jay Famiglietti: Nearly 30 years ago, NASA launched its TOPEX satellite. It measured the topography of the ocean and gave us a better sense of how sea levels are changing. Today, from space we see oceans rising fast. With 40% of humans living in coastal areas, rising sea levels threaten billions of lives.

I’m Jay Famiglietti. On this episode of What About Water? it’s a look at our oceans from orbit and how communities prepare and protect their coastlines.

Steve Nerem is a Professor of Aerospace Engineering at the University of Colorado Boulder. He’s a principal investigator on NASA’s Sea Level Change team. We’ve reached him in Colorado.

Steve, welcome to What About Water.

Steve Nerem: Thanks Jay, happy to be here.

Jay:  It’s so great to see you. We should let our listeners know that you and I go way back, uh, starting our faculty jobs at University of Texas at Austin and you and your colleagues getting me interested in space geodesy and sea level rise and the NASA, GRACE gravity recovery and climate experiment mission for which, you know, I’m eternally grateful. Thank you. And you and I have had some great collaborations too, so that’s been a lot of fun.

So take us back, and let’s talk about TOPEX. Why did we launch TOPEX 30 years ago? What, what were the goals?

Steve: Well, as you were saying, you know, the main goal was to measure the ocean circulations. So measuring sea level change was really not part of the original mission goals for TOPEX.

Jay: And so when did you realize that there was this great information on sea-level and sea-level rise?

Steve: Well, it was about the mid 1990s, so maybe 2-3 years after TOPEX launched. And my recollection is I was just sitting around my office one day and I thought, Uh, you know, I knew about sea level change and, uh, especially global average sea level change. And I thought, well, what if I just try to compute it and see if it looks reasonable? Even though I kind of knew in the back of my mind that the errors were going to be too big to detect it. And lo and behold, we did the calculation and we saw, you know, a very distinct seasonal signal that looked real.

And so then we’re like, huh, maybe we can do this. And that’s kind of how it got started.

Jay: Isn’t that amazing? You know, you get in there and you’re maybe after something else, but then, you know, I think that’s the beauty of science. Like you’re looking at the data and you know, you try something out and it’s like, wow, this is, this is crazy.

And since TOPEX launched, NASA sent up some other satellites like the GRACE mission that I mentioned. So how do, how do these things work?

Steve: So TOPEX we’ve launched a whole series of missions. Now, Jason, one, two and three, and then sentinel six. But all these missions basically work very simply.

You, uh, you have a radar on board the satellite and you fire a radar pulse at the ocean surface which bounces off the ocean surface and goes back to the satellite. Satellite measures how long it took for that pulse to go down and come back. And from that, we can determine how high the satellite is above the ocean surface.

Of course, that doesn’t give us what we need yet, because we want to know what the height of the ocean surface relative to, say, the center of the earth. And so that’s where this field of, uh, orbit determination comes in, where you have all this precise tracking data. And the one people will be most familiar with will be like a GPS receiver, not unlike what’s in your cell phone, but we have one onboard the satellite.

And we can determine the orbit of that satellite to an accuracy of a centimeter or two.

Jay: Wow.

Steve: So about an inch. And so by taking the height of the satellite relative to the center of the earth, say, and subtracting off that radar measurement, that gives us the height of the ocean surface.

Jay: That’s amazing.

Steve: I mean, there’s –

Jay: That’s amazing.

Steve: It’s a pretty simple measurement and we do it very accurately. You know, you can determine global average sea level to, you know, a few millimeters.

Jay: That’s amazing. So just to give people a sort of a picture when we’re, when we’re talking about like Topex orbiting around, like how many sort of individual measurements? Are we talking about 10? Are we talking about like, you know, a million or like several million?

Steve: The orbit, uh, covers the earth between plus or minus 66 degrees latitude. That orbit, uh, repeats every 10 days. So the track it follows exactly repeats every 10 days, we designed it that way. And within that 10 day cycle, there’s something like half a million measurements, uh, over the earth. So we’re definitely data rich.

Jay: Right. But then in that, in having all those measurements, you’re getting, um, you’re reducing the errors, you’re reducing the uncertainties. Right? And you’re also getting a spatial picture too, right? Like, uh, the, you know, the topography of the ocean.

Steve: That’s right. And the, uh, you know, for so many years now, the plot that has gotten the most exposure to the public and the press has been that global average sea level plot.

So every 10 days you average all the data over the map, and you plot a point on the grass. And so we’ve been watching that global average go up, but more recently we’ve been focused more on the map of sea level change. So there’s a map that goes with all that data. And so we’re looking at the trends on that map and that’s really in the past couple of years, we finally have enough data that we can see the impacts of greenhouse gases on that map.

And what it tells us is that sea level rise is not the same everywhere.

Jay: Wow.

Steve: Since you know, Topex launched in 1992 global average sea level has gone up about nine centimeters during that time. But there’s been a lot of variability. I mean, there’s some places where sea-level has fallen a little bit, like down or near Antarctica, and then other places like in the Western Pacific where it’s gone up twice that amount. So it’s gone up 16, 17 centimeters.

Jay: Wow.

Steve: That’s kind of the pattern due to how the ocean, uh, stores its heat mainly. And so we’re studying that very carefully because we feel like it’s definitely telling us something about what the future patterns of sea level will look like. And so the key is, okay take the pattern you’ve observed over the last 30 years, and what does it tell you about what the pattern is going to look like in 2050 or 2100?

Jay: So when we talk about the global average, right? Mean sea level rise. You mentioned nine centimeters over there for over the last few decades. What are the current rates?

Steve: So the rates started out, you know, when TOPEX launched, it was about two millimeters per year of global average sea-level rise, but it’s accelerating.

And so the rate increases about 0.1 millimeters per year, every year.

Jay: Wow. I, I, okay. Wait, wait just a second. I didn’t know that the rate of acceleration was that great.

Steve: Yeah, it is, so that means if you do the math, uh, over 30 years, that means we’re starting to approach five millimeters per year.

Jay: Wow.

Steve: So probably, and if not this year, then next year we will pass five millimeters per year.

Jay: That’s amazing because, you know, I remember when we first started talking and we’d write proposals and I would just say like, “Hey, it’s like, you know, two millimeters per year.” And then at some point it was two and a half, and now we’re looking at headed towards five. So we’ve got five millimeters per year now. Okay. That’s – that’s not good.

And then we’ve got these patterns that we can start to relate to things like currents and El Nino and La Nina and climate and climate change, which is, which is pretty scary. Like, some people will hear five millimeters per year and they’ll think like five millimeters that’s nothing.

I mean, what does it mean in a practical sense for people that live on the coasts?

Steve: Yeah, it’s obviously not good news. If you kind of extrapolate those numbers forward – in fact, we’ve got a paper in review right now where we’re doing exactly that and just extrapolating it forward, assuming that things continue as they are, so basically it’s looking at the trajectory – and if you do that, you get about 21 centimeters or so by 2050, and about 65 centimeters of sea level rise by 2100. You’re heading up towards, you know, that meter-type sea level change, which, you know, in the back of my head, I have always carried a meter as kind of the breaking point between sea-level change that’s a nuisance, but that we can probably deal with and sea-level change that becomes catastrophic, where, you know, you have to abandon some cities and things like that.

Jay: You said what 60 something centimeters by the, did you say like your projections by the end of the century?

Steve: That’s just, if we just take the current trajectory, we get to –

Jay: Yeah, without the acceleration –

Steve: 65, no with the acceleration, –

Jay: Oh, okay.

Steve: We get to 65 centimeters by 2100, but that’s just assuming everything continues to change as it has over the last 30 years. And we know particularly in the ice sheets, uh, that there could be rapid dynamical changes in the ice sheets that might significantly increase that number.

Jay: Okay. So, very scary because you’re talking about numbers that, we already know that we should be really careful on our coasts nd making preparations and thinking about managed migration.

But you’re talking about in less than eight decades now is, um, actually catastrophic. And I want to just follow up on the why. So, you know, where does the water come from that is driving sea level rise?

Steve: So there’s kind of two main sources. One is thermal expansion.

The oceans are absorbing more than 90% of the heat from climate change, which is great for us. Things will be a lot worse if we didn’t have the oceans. But the ocean water, as it absorbs heat, it expands. It’s just like mercury in a thermometer. You know, you heat up the mercury, the mercury expands its volume and it goes up the tube and the oceans you heat up and the volume expands and sea level goes up.

So that’s one major effect. Then of course the other one is the, effectively on some simple terms, you could say it’s the exchange of water between the continents and the oceans. And the one we of course hear about the most is the melting of ice because you know, the melting of ice in Greenland, the Antarctica mountain glaciers, because it’s very hard to put the ice, uh, back up onto the continents, once it melts and goes in the oceans, it’s hard to reverse that process.

Now, of course, you’re a hydrologist and so there’s also other hydrological considerations that we do see show up in sea level. Most of that contributes to the inter-annual variability and sea level. And the ones that really worry us, are the trends from the ice sheets and, and the ice sheets are, uh, also the, kind of the source of biggest uncertainty, because, you know, glaciologists still can’t really figure out how quickly those ice sheets are gonna melt as we go over the next a hundred years or so.

Jay: You know, you can’t go really build a model, like a physical model of an ice sheet and study how they fail. I think, is it fair to say that sometimes, the community, you know, we’re surprised by some of the mechanical processes, the rapid breakup and the potential for more rapid breakup in that, that sort of stuff isn’t in our model so that our models may, unpredict?

Steve: I’m not a glaciologist. Uh, I work with a lot of glaciologists and talk to them a lot about the problem. You’re right – you can’t really build a real size model of a huge ice sheet and so, you know, you’re using other tools, computational tools, and then you’ve got these new processes that someone might come up with about how the ice shelves may, may fail and things like that.

Jay: Yeah. It’s time for us, you know, our generation to be, uh, thinking about centuries. Right? And thinking about the decisions for the sustainability of the planet in the coming centuries.

Steve: Yeah.

Jay: So listen, I want to bring this back to people. You know, these numbers that we’re talking about, if you’re living on the coast, or somewhere, what are we talking about? What are people going to start experiencing?

Steve: Well of course, you can live on the coast and still be many meters above sea level. So it’s, you know, you would have to look at your individual situation, but if you’re near sea level, you know your first experience with sea level rise impacting your property is going to be through nuisance flooding.

So when you take the sea level rise, then add to that the effects of tides and storms…like on the West Coast, they just went through a big king tide period where they had some flooding in certain areas. When you layer on sea level rise, tides, and then storm events, that’s when you’re going to get wet the first time.

Jay: That’s um, that makes me uncomfortable, Steve.

And so the nuisance flooding, that’s the kind of stuff I think that we’ve been reading about in Miami. Right. And in Florida. And I didn’t actually realize that it was happening on the West Coast. So. Uh, thank you for, thank you for sharing that.

I know, you know, from my work that rising sea level can impact coastal groundwater and contaminate it, right? Sort of add seawater to groundwater that’s near the coast. What else do you in your community think about?

Steve: Well, you know, the NASA sea-level change team works closely with, uh, people who are involved with, you know, stakeholders, as we call them, grow involved in these activities. You know, the coast, you try to categorize things in terms of what the risk is, you know, like a nuclear power plant, you might have one set of requirements, a hiking path, you might say, “oh, it’s okay. That’s okay, if it gets flooded.” Then there’s everything in between. Right? And so we’re trying to provide as much of the science as we can to the stakeholders so that they can make the best decisions going forward about what their communities need.

Jay: So yeah. Thank you for sort of providing that, that sort of spectrum of urgency and the nuclear power plant is one that, you know, hits home because again, you know, there was the San Onofre plant that was on the beach. Now it’s been decommissioned, but it’s an interesting example. Another thing that there are a lot of on coasts are water treatment plants.

And so that has implications for like, you know, city sewers and getting inundated from, from rising sea level. So let’s pause for just a second here and take a quick break.

Steve: Alright, thanks.

Commercial break

Jay: Okay. We’re back with Steve Nerem of CU Boulder. So Steve, we know sea level rise is happening and it’s happening faster than we expected. Is there a way to stop it? Can we slow it? You know, who, who could be taking this kind of action?

Steve: We can definitely slow it. One of the things, Jay, to know about sea-level is that as you warm the earth, the processes that cause sea-level change are very slow to respond to the warming.

You know, the warming that we have today, we’re going to see that sea-level change a hundred years later or more. And so, we look at – the term that’s used in science is “sea-level commitment.” You know, what have you committed to in the future by the changes you’ve made today? If we can keep warming to, you know, one and a half degrees centigrade, then we can probably keep sea-level to two to three meters (sea level rise).

If we don’t keep warming the 1.5 degrees, then it just goes up from there. And that’s how you get to the 5, 6, 7 meter numbers, is if we don’t do anything. So while we can’t stop, you know, say a meter or more of sea level change, we can, if we can get active in reducing our greenhouse gasses, we can head off some of these huge numbers that you see later.

And you know, when I think about huge numbers, if you look, you know, Greenland has approximately six meters of sea-level locked up in it’s ice. Antarctica is, you know, 60 meters. So there’s big numbers out there now. We’re not going to melt all that ice, but you know, you start melting even a fraction of that ice and you get catastrophic numbers that, uh, for the cities along the major cities along the coasts would be really bad news.

Jay: When we hear about, you know, one and a half degrees, two degrees, whatever the number is that we can sort of stabilize climate at, I don’t think that that amount of sea level rise is getting the messaging that it should. Or if we go beyond that, we’re talking about meters, you know, maybe in the next century.

That is a tremendous amount. And, you know, if not sooner, if the ice sheets disintegrate more rapidly. That’s a tremendous amount of water. Um, that is….the global impact of that, I’m not sure the message is out there. And what strikes me is that, you know, it can’t just be a few of us, this is a global effort.

Steve: Ya you know in some ways, uh, I think you’re right, that the message isn’t getting out.

And yet you could argue that sea level rise is going to be the most important thing that people are going to see as a result of climate change. So, you know, it’s not just the rise in temperatures. This is going to be catastrophic, you know, very hard to adapt to, very hard to build coastal protections for that kind of sea level rise.

For up to a meter you could imagine protecting some of your most valuable assets, you know, like New York City and places like that. But once you get up into the multiple meters, you know, you have to look at like turning New York City into the Venice of the East coast or something like that.

Jay: So, uh, I wonder if people are actually thinking about that because that, that is the way the things are going, but there’s really no way to, you know, there’s no way to stop it.

Right. I mean, you’ve sort of answered it, but let me just ask you directly. Can we stop this?

Steve: I think we can. The question is: what number do you stop at? You know, the,

Jay: Okay, so we can’t stop it. Like we’re committed to sea level rise. To some amount.

Steve: We’re probably committed. We’re probably committed to two to three meters at least.

Jay: Okay. That is insane. And this is the first time that I’ve heard that. So let’s all take a moment and think about what that means. So Steve, let’s be clear on something. You’re talking about a commitment to – meaning it will happen – to two to three meters of sea level rise. Where is this information coming from?

And what’s the timescale over which this is happening?

Steve: So about every seven years, all the governments in the world get together and the Intergovernmental Panel on Climate Change, they produce an assessment report every single seven years. And what they do is they just go out and assess all the scientific literature, the journal articles and everything that has come out.

And they kind of bring it all together and come up with an assessment, you know, an overview of what the state of knowledge is right now. So the last one came up just recently and I just pulled my numbers from them. So the number of two to three meters is (now to be fair, that’s probably not till like 2300) but that’s, that’s due to warming that’s happened today. So when we say commitment, that’s the warming that’s already happened is going to cause up to a meter maybe by 2100 and then it’s going to continue rising. You know, if we stabilized our greenhouse gasses today, we’d still get to two to three meters.

Jay: So my interpretation of that is that we’ve screwed the next two centuries of humanity.

Steve: We’ve certainly created major problems for them. That’s for sure. Then you have to go look at, what do you do on the coast? You know, it’s interesting – this is kind of an aside, Jay – but I often get questions from people in the public who will pull me aside and say, “I’ve got my condo right on the coast in Florida. Can you tell me, should I sell it or should I keep it?”

You know, my answer is always, well, you know, this is just for you to enjoy your retirement for the next 20 years – because most of these people are seniors – I’m like, go enjoy your retirement. You might have some nuisance flooding, but you’ll probably be okay, you know, unless you get a direct hit from a hurricane or something like that.

Jay: Oh yeah, there’s that.

Steve: But on the other hand, if this property is an investment property that you want to say, be part of your inheritance to your kids, then by all means sell it because the property values are already going down because of this realization of their exposure to sea level rise. Your kids are going to be the ones who are going to be most impacted by this. And it doesn’t do them any good to have a coastal property that’s getting flooded, you know, 10 times a year.

Jay: And now how can we stop it from going further?

Steve: We basically have to stop taking those fossil fuels out of the ground and burning them. So there’s lots of things we can do, but that I think is the most important thing we can do.

There’s a lot of other geoengineering-type approaches, but there’s a lot of risks. I’m not an expert in geoengineering, but from the articles I read – and you probably read the same articles – there’s a lot of uncertainty there, particularly in your field of hydrology, a lot of uncertainty about what geoengineering does to the hydrological cycle.

Jay: Human resilience. Do you think we can adapt?

Steve: That’s a good question. I, you know, I have a lot of faith in human beings to be able to innovate and come up with technological solutions and things like that. So, I think we will adapt, but it will be at significant expense and that expense, uh, will not fall evenly on all the countries in the world.

Jay: Yeah.

Steve: And so, you know, you don’t know how all that’s going to play out, you know, even big countries like the US might not fare well in a future scenario because they have so much expensive infrastructure near the coast.

Jay: I used to think I was the doom and gloom guy, Steve, but, uh, after this conversation I may have passed the mantle.

So let me wrap it up by asking you, do you see any hope? Where do you see hope in all of this?

Steve: I suppose I see hope because it always amazes me what we’re capable of, technologically. I mean, just look at our careers, Jay. I mean, you know, the internet came out about the time we got our PhDs. You know, we’ve only had smartphones for the last 14 years.

I mean, the technology is really accelerating. And so why would I hesitate to say that we can kind of ‘technology’ our way out of this. Because that’s not a message that I want to really put out there because I want to see people reduce their greenhouse gasses, and reduce their carbon footprint. But I do have a lot of hope for society that we can beat this problem and solve it.

I do see hopeful signs out there in the community that even people who didn’t really believe in climate change before are starting to come around.

Jay: I think they’re going to have to, when the nuisance flooding becomes more nuisance flooding and it becomes catastrophic. But I want to follow up on something. So you’re saying that, you know that we have a commitment to two to three meters of sea level rise. So like we’re not stopping that. It sounds to me like what you’re talking about is people’s ability to, you know, the resiliency of the human race to adapt to that change. And maybe also stop burning fossil fuels to slow the rate of melting and warming.

Steve: There’s no silver bullet here. So it’s going to be lots of bullets. It’s going to be reducing greenhouse gases. It’s going to be technological solutions. It’s going to be building coastal protections. It’s going to be new energy sources. It’s going to be a lot of things that are going to get us, move us forward. And that’s my hope is that we will take every one of those things. We can’t just expect one thing to solve it all.

Jay: That’s very sobering. Steve, thanks so much for joining us today.

Steve: Thank you. I’ve appreciated the chance to talk about this.

Jay: It’s, it’s been great. And it’s been great to reconnect. Thanks again Steve.

Steve Nerem is the Principal Investigator with NASA’s Sea Level Change team. He is a Professor of Aerospace Engineering at the University of Colorado Boulder. He’s also a fellow in the Cooperative Institute for Research and Environmental Sciences at CU Boulder.

Last Word

Jay:  For coastal communities dealing with sea level rise now, and preparing for the future – adaptation is key. On the southwest coast of British Columbia, sea level is expected to rise 1 meter by the end of the century. Researchers, municipalities, and First Nations there have come together through “Living with Water” – a $1 million dollar, 4-year project creating local, nature-based solutions to protect their communities and coastal habitats.

Matt Osler is a Senior Project Engineer for the City of Surrey, a fast growing city in South Western British Columbia home to about half a million people.

Matt Osler:  Adapting to sea-level rise is a really complex problem. Our shoreline for the most part in Surrey, the ground is gradually sinking through what we call ground subsidence. And in terms of the rate, we’re estimating it to be about two to three millimeters per year. so over a century that would be 20 or 30 centimeters or close to one foot. And then that’s on top of any global sea level rise that would be occurring.

The concern is that with sea level rise that a lot of the different types of vegetation will essentially drown by becoming submerged by water too often. So what we’re trying to do is be proactive and help the vegetation adapt to the higher water level, so it can continue to flourish, to provide critical habitat for migratory birds, for example for fish, but also there’s a co-benefit for flood protection because, the vegetation can slow down the waves and attenuate a lot of that wave energy and erosion that comes with it from the shoreline.

So we have a section of shoreline that’s in wildlife management. And before the wildlife management area was established, a traditional earth levy was constructed. And then after that a highway came right beside the levy. So there’s no room to really build the dike higher because of the highway being so close and we want to reduce or, if possible, even improve the environmental condition within the wildlife management area.

So the concept is called a living dike where we can enhance the existing saltmarsh to provide better ecosystem services but also attenuate wave energy to reduce the flood risk to the highway and the land behind the highway.

So you can imagine, there’s an intertidal area – that’s the lower area – is mostly mud flat. And then as the slope gets higher, towards the land, you start to see more grass species in the foreshore area.

Having researchers who can tackle all the different elements from the policy gaps to the governance issues to the actual solutions themselves and put forward the comprehensive research program is, I think, the key to actually being able to make a difference.

Jay: That was Matt Osler. Matt oversees the implementation of Surrey’s award-winning Coastal Flood Adaptation Strategy. You can learn more about Living with Water at the Pacific Institute for Climate Solutions.

That’s it for this episode of What About Water? We record and produce this podcast on Treaty 6 territory, the homeland of First Nations and Métis people.

It’s produced by the Walrus Lab and the Global Institute for Water Security at the University of Saskatchewan. For more resources, check out whataboutwater.org. 

Our crew here at What About Water? is Mark Ferguson, Erin Stephens, Laura McFarlan, Fred Reibin, Jesse Witow, Shawn Ahmed, and Andrea Rowe. Our audio engineer is Wayne Giesbrecht and our producers are Farha Ahktar and Jen Quesnel. What about Water is available on Spotify, Apple, and wherever you download your favorite podcasts.

I’m Jay Famigiletti. Thanks for listening.