Scientists Concerned By a Sudden Increase in the Rate of Sea Level Rise

0:00There's been a sudden increase in the rate of sea level rise as measured by satellites. data suggests that around 2012 it's suddenly accelerated and it's remained higher ever since yeah you know we talk about a poly crisis and all the different impacts of global heating you know floods droughts wildfires food security ecosystem collapse and you know all of that stuff and a lot of them uh are starting right now we see them you know they're in the here and now yeah yeah but but i can't keep them all in my head and one that kind of gets displaced yeah is sea level rise i feel because putting aside the very real problems in the South Pacific and those islands that are disappearing, it does feel like something further away.

0:41A future problem, a slightly less immediate one. But unfortunately, there's no way of getting away from it. And that's what we're getting into on this episode of The World, The Universe and Us from New Scientist. I'm Dr Penny Sarchet. And I'm Dr Rowan Hooper. And we're joined by reporter Michael LePage. Michael's just back from Vienna, the European Geosciences Union meeting. and you've heard some new information about sea level rise and what's the top line? Yeah so to start at the beginning we already know that sea level has risen by more than 0.2 meters over the past century or so and this has been caused by a number of things so there's the ice caps are obviously starting to melt we've got mountain glaciers melting there's also the water the oceans are getting warmer and that water is expanding as it gets warmer now in terms of the overall level of sea level rise.

1:32We've only had satellite measurements since about the 1990s, so we've only got about 30 years. And over that 30 years, it looked as if the rate of rise was quite steady at around 3.6 millimeters a year. But now, as more information has come on, so a team of researchers have spotted that there seems to have been a step change. So in fact, it's gone from 2.9 millimetres before 2012 to 4.1 millimetres a year now. So there's a sudden sort of jump around 2012. And so that jump, it's just over a millimetre. It's quite large if you think about the time span that that's happened in. It must be due to global warming, right?

2:12I mean, it's possible that it's due to natural variation, some change in the oceans. Yeah, but it's not, is it? Yeah, I mean, it could well be due to this sort of accelerated rate of warming you've been seeing recently. Yeah. And of course, we're talking about millimetres. But remember, you know, an extra, if this is an extra millimetre a year over a century, that adds up to 10 centimetres, which is a lot. Yeah. And of course, we're expecting. And that's on top of the rise that's already happening. Exactly. Yes. Well, I think a millimetre a year is quite a lot. I mean, it feels like a bit like glaciers retreating and maybe, you know, there is a correlation between that.

2:50We'll get into that. But that you mentioned the rate of warming is increasing. And that's something that was for a while was controversial. And then we reported on a study earlier this year. It was an analysis of five different temperature data sets. And that found that the rate of warming had doubled from 0.18 degrees Celsius per decade prior to 2013. 2014 to about 0.36 degrees celsius a decade after that so that's quite that's a you know doubling in warming in the rate of warming so this new analysis of sea level rise you know the step change we've looked at very closely seems to map this change in the increase in rate of warming yes and in terms of sea level uh if you look back and you put sort of we've got all this old tide gauge data going back more than a century and if you put that next to the satellite data it's very clear that we've seen an acceleration a gradual acceleration in rate of sea level rise so tide gauge literally means those sticks that people have in the in the docks at the old seaside towns and stuff exactly yeah yeah yeah so if we if we go back to the start of the 20th century uh we were seeing a rise of maybe a millimeter a year a bit more than that and now based on this latest study it's up to over four millimeters a year and if it keeps on increasing obviously things get worse and worse in the long term.

4:14So the team that presented this finding at the conference did their analysis suggest anything about what's causing this increase in the rate of sea level rise? Well they can't be sure but obviously they're speculating that it's linked to this acceleration in global warming that we talked about and that acceleration in turn is linked to the decline in aerosol pollution. So basically we had the situation where one of our pollutants, aerosols, has a cooling effect and was counteracting the impact of another of our pollutants, CO2, which has a warming impact. And so if you keep on emitting CO2 and you take away the aerosols, you get a sudden increase in the rate of warming.

4:53And just to spell out the aerosol thing, we're talking here about things like sulfur dioxide emissions from shipping and the dirty emissions from coal power stations and from vehicle exhausts, especially from China, where that has screened out sunlight, right? It's been this natural geoengineering project, really. Yeah, I mean, the effects are very complicated. But basically, overall, it has a cooling effect by reflecting some sunlight back into space. So, I mean, it's unfortunate, but it's obviously a good thing that pollution is being cut down. is that over now and we can kind of get on with it or is there more of this sort of unmasked warming yes um it's it's not a pretty picture at all so in terms of emissions of aerosols they've only halved from the peak in the 1980s so there's a lot more aerosol pollution to cut and then it's estimated that if there had been no aerosol pollution at all the world would already have warm past two degrees celsius so that's the amount of warming that's in the pipeline just with the co2 emissions up to now and of course we're still emitting more co2 and those emissions are still going up every year not going down that's right i'm glad well i'm not i'm kind of glad to hear that but like i had heard some people saying we can expect warming the rate of warming to sort of go back down again um because they hoped this unmasking was over now and this hidden warming has been released, but no.

6:22Well, and it will happen eventually. Yeah, but not until things go really bad. Yeah, we've got, yeah, not for a very long time. Yeah. One thing that stood out to me in your reporting on this is that I think there's a very sort of simplistic narrative that we all learned that when you've got global warming, you've got the ice caps melt, the sea level rise, but there's actually multiple, like so many things in climate change, there's actually multiple reasons that sea levels rise as a result of global heating. Yeah, so there are lots of different causes, and I think one that is often neglected or overlooked is the expansion of ocean waters.

6:54And so as water warms up, it expands a little bit. But if you look at the whole oceans, that obviously adds up to quite a big effect. Now, we've been measuring, we have quite good measurements of the top two kilometres of the oceans. We have these sort of Argo floats that go up and down in the water and they measure those temperatures. We know what's happening in those first two kilometers. But there was a study presented at the EGU where they sort of thinking actually now the warmth is even penetrating deeper than two kilometers. We can't measure that directly. But this study, they were basically adding up all the factors that we know are contributing to sea level.

7:35So, you know, ocean expansion, mountain glaciers melting, the ice caps melting, all of these different things. it's also actually there's less fresh water stored on land is another surprising one we've seen a sort of transfer of water from on the land to in the ocean that's not one i i realized was an issue yeah yeah but anyway so this this study of the when you add up all these different factors they from 2016 they no longer add up to the observed rate at sea level rise so this study looked at sort of satellite data and did some modeling and they say this gap can be explained if we're now getting warming of the oceans below two kilometres, which is, yeah.

8:15But we hear a lot about how much the ocean has soaked up the amount of heat that we've put into the system and in a way bailed us out. But if we're saying that we've started to heat up that top two kilometres and now we're even going into the deeper ocean, I wonder what that says about how much more capacity there is in the ocean. Well, I mean, I think there's, you know, water has a huge heat capacity. The oceans have soaked up more than 90 % of all the extra heat energy that the planet's taking in. Wow, as much as that? Yeah. 90 %? 90 % of the heat energy. And if the deep ocean's warm, there's a tremendous amount of heat that can be stored there.

8:57But of course, if that heat is stored there, there are two issues. First of all, we're going to get expansion of the waters and more sea level rise. But also that when it comes to trying to cool the planet back down, you've got all that heat that you then is slowly going to be released over centuries and millennia. Yeah. And so you talked about that second study that found there was this gap between this sea level rise that we're seeing and the sea level rise we expected. And that this deep ocean warming seems to be maybe responsible for that gap. How much then of the sort of total annual sea level rise is the deep ocean contributing to?

9:31Well, so they estimate that below two kilometres, it's 0.4 millimetres a year. So that's about a tenth of the total. Exactly. Right. Which is obviously pretty significant and will become more significant over time as that ocean, as that heat keeps going deep in the ocean. And so then this 4.1 millimetre rise that we're seeing annually, that's already, of course, bad and an existential threat for low-lying islands. You mentioned the South Pacific, right? Yeah, well, and also, you know, Venice, there was a report out recently about Venice and New Orleans that basically effectively written them off in terms of that there's very little we can do now to save those places.

10:13As shocking as that is, that's starting to feel quite familiar, but we're not really thinking about the longer term forecast and all of the other places. Yeah, exactly. Well, that's the point. Those places are already now at the edge of what they can do to protect themselves against sea level rise. And that's at 4.1 millimetres a year of warning. So, you know, it's not looking great. So what is that longer term picture? Yeah, I think it's hard to exaggerate just how bad it is. That's not how I wanted that sentence to go. So, and I don't think governments have really taken this on board yet. So if you look at the official predictions from the Intergovernmental Panel on Climate Change and its last report, so for an intermediate emission scenario, it is forecast or projecting rather a sea level rise of around a metre, which is pretty bad.

11:05For its worst case scenario is nearly two metres of sea level rise. And that's by 2100. And then it could be five metres by 2150. Five metres. Five metres. Yeah, I mean, it's unbelievable. But the thing is, I don't think we're on that worst case scenario, but we're not far off. And I'd say we're in between that and the intermediate scenario. Even an intermediate, even a not so bad scenario is bad. You know, it's catastrophically expensive and damaging, isn't it? Yeah. And the thing is, sea level rise will not stop in 2150. You know, it's a kind of slow motion disaster. It's really hard to get started.

11:45and then once it's underway, it's really hard to stop. I mean, I think of it sometimes like you have those old freezes where they got completely frosted up, you know, to try and defrost them. And you try all sorts of things to warm it up and nothing would happen for ages. And then suddenly you would start to see the sort of ice melting and everything, bits would fall off. And it all happened very suddenly in the end after spending ages trying to start. And I think, you know, what we're going to see in the coming centuries is a bit like that. And now we've got 0.2 meters so far. It doesn't seem that bad, but it could be a meter by 2100.

12:20And then it's just going to keep on going up from there. So take the West Antarctic ice sheet. A lot of researchers think it's already past the tipping point where it's going to melt whatever we do. Now, that's three meters of sea level in the pipeline at some point. We don't know when, but it's going to come. Greenland, that's six meters of sea level rise, Greenland. A lot of researchers think if we haven't passed the tipping point already, we're getting close to it. So that's six metres plus three metres. That's nine metres of sea level. You keep on adding up this list, you can get to 20 metres, potential sea level rise very quickly.

12:55Now, of course, I'm talking in the long term here over centuries and millennia. But the point is, once you set it in motion, it's really hard to reverse it. There may be no way that we can reverse many of these things. Well, yeah, you mentioned, you know, governments are not thinking about this then and they famously don't think about long term, even not as long as you've been thinking, even 100 years, 50 years, they don't think. It makes me think of the Kim Stanley Robinson book, The Ministry for the Future. We should have a ministry for the future, an international agency that is tasked with planning, literally planning for these sorts of events.

13:35Yes, unfortunately with the political cycle typically being four years, just that long-term vision. That's why there needs to be some overarching agency which does have the foresight, the capacity to sort of start implementing these sorts of things. That's what should be set up. But, you know, we were talking about sort of places like Venice and Tuvalu and there's that Pacific Island that's going under. But, you know, New York and Shanghai and London, all of these places are going to see, you know, very serious flooding from the seas. that just gets worse and worse. And we're still merrily building away in places that are going to definitely get flooded by the sea.

14:10It's crazy. Did you ever see Waterworld, the Kevin Costner film? It's not going to be as bad as that. Well, I just looked it up. That was like 7 ,000 metres of sea level rise in that film. So that entirely covers the world. I don't know if there's any land left on the planet, but that is a post-apocalyptic Earth on that. it's not like another world that's a water world it is earth in the far future but yeah we're not going to get as bad as that we have found a bit of optimism a silver lining after all most of the continents are well above the level that could be submerged but the trouble is we've built around the edges all our cities and stuff are on the edges of the sea where they can get flooded that's all for this episode, thanks to our guest Michael LePage and thanks to you for listening And do follow and subscribe wherever you get your podcasts.

15:03Bye for now. Bye. Bye.