Study Finds Sea Levels Rising at an Unprecedented Rate
Kurt Lambeck, professor of geophysics and former president of the Australian Academy of Science, says sea levels have risen at an unprecedented rate in the last 150 years, as compared to the 6,000 years preceding it.
SHARMINI PERIES, EXEC. PRODUCER, TRNN: Welcome to The Real News Network. I’m Sharmini Peries, coming to you from Baltimore.
Sea levels have risen at an unprecedented rate in the last 150 years as compared to the 6,000 years preceding it. Is this due to the Industrial Revolution and CO2 emissions?
With us to discuss a study titled “Sea Levels and Global Ice Volumes from the Last Glacial Maximum to the Holocene”, published in the Proceedings of the National Academy of Sciences, is its lead author, Professor Kurt Lambeck. Lambeck is professor of geophysics at the Australian National University in Canberra, Australia. He is past president of the Australian Academy of Sciences and a member of the Antarctic Ecosystem and Environment CRC. He has published extensively–over 250 papers and two books. You will find more of his eminent qualifications just below the player here.
Professor Lambeck, thank you so much for joining The Real News.
KURT LAMBECK, PROF. GEOPHYSICS, AUSTRALIAN NATIONAL UNIVERSITY: Thank you very much, Sharmini.
PERIES: So, Professor Lambeck, let’s start with your key findings of the study.
LAMBECK: What we set out to do was to understand the relationship between sea level and climate on glacial cycle periods. So we started back 30,000 years, 35,000 years, up to the present. And that’s an important period, because it’s a time when we’re going into an ice age, it’s during an Ice Age, and it’s coming out of the ice age into the present interglacial.
And one of the reasons we want to do this is to try and to use this record to calibrate other indicators of sea level change, other indicators of climate change, so that we can get a better understanding of what may have been going on further back in time, during the complete glacial cycle. And in that process, of course, we begin to understand lots of things about how the Earth works, and particularly the interactions between the Earth, the ice sheets, and the oceans.
Now, one part of that study has focused on the current interglacial, this period of the last 6,000 years or so, when sea levels have been roughly the same as today. And we’ve used a lot of geological data from that period to put together a function that describes the changes in the ice volume. And that, of course, relates to the changes in sea level. So that’s essentially what we’ve done. And this part of what’s happened in the last hundred years is just the tail end of that study, really.
PERIES: So, Professor, the rise in sea levels due to ice melting and its consequences of thermal expansion seem to be really coinciding with the CO2 levels that we’re experiencing now. Is this due to human activity?
LAMBECK: Yes, what we see in the record for the last few thousand years is that in the early part of that time interval there was a slow rise, which was the residual melting of mountain glaciers, contributions from the Antarctica, for example. But in that period, I think the important result is that we don’t see evidence for wild oscillations in sea level. If you look at the literature, you sometimes see references to sea level going up and down by as much as a meter or more in short periods of time during these interglacial periods. What we found is that when you put all the global information together and you allow for land movements, then there’s really no evidence for such oscillations, and that the sea level during that period, until, say, 150 years ago, 100 years ago, has been relatively stable. That I think is the important result.
And then, when we look at what’s happened the last 100, 150 years, we see, of course, a rise in sea level at a typical rate of a couple of millimeters per year over, say, 100 years. So we’ve seen a 20, 25 centimeter rise in sea level in that last hundred years. Insofar as the resolution of our geological data allows, we see no evidence for similar changes on a time period of 100 years, 200 years that we see today. So from that we would have to conclude that something different has been happening in recent times that we haven’t seen in the past few thousand years.
PERIES: And so the rate at which the Antarctic ice caps are melting and raising the sea levels, it is having tremendous impact, perhaps, in our coastal areas. Describe what some of the devastating impacts might be. Or did you get into that in your study?
LAMBECK: Well, no, we don’t. The study, we purposely focused on this past record, on establishing the record, to address the potential consequences, the future consequences of this.
But I should just make it quite clear that we cannot–I do not say that it’s necessarily coming from Antarctica. What we’re saying is that we see changes in the volume of the ice over a long period of time, and then we indirectly try to infer where it’s come from. So a lot of it has come, of course, from the melting of the North American ice sheet in the past, the European ice sheet, etc., and some has come from Antarctica. And that, in fact, is one of the important bylines of this study is that we’ve been able to quantify the changes that we think have occurred in Antarctica since the Last Glacial Maximum.
But let’s put that aside and let’s focus on the last few thousand years. I’d just reiterate: we don’t see evidence for oscillations of more than plus or minus, say, 20, 25 centimeters on timescales of 100 years or so. And when we look at this precise record for the recent times–which we haven’t used in our study, incidentally–we do see that different behavior. And the question is: what is that different behavior caused by? I don’t think it is due to the background signal that we see in the geological record, so something else is going on. What that something is is no doubt the thermal expansion of the ocean. And our models of the ocean system and the warming of the oceans suggest that at least half of that signal that we see today could be due to thermal expansion. And the other part is coming from the melting of mountain glaciers, for example, and possible contributions from Antarctica and from Greenland.
I cannot say precisely what comes from Antarctica, what comes from Greenland. Is Antarctica melting? Or is it actually growing? But that would mean there’s more water coming from Greenland. Those are issues that we cannot address from this study.
PERIES: Professor Lambeck, based on your findings, are you doing any projections in terms of the rate at which things are melting and what we can expect in the future?
LAMBECK: We’re not doing any ourselves at this stage. That requires a different set of talents. But I work with colleagues, with oceanographers, for example, who have those abilities, and they have been doing this work based on scenarios of what happens if there is global warming, how much of that heat in the atmosphere goes into the oceans, what does the thermal expansion do, etc. So there is a lot of modeling going on in that area, and I don’t think there’s anything that I can or intend to contribute to that particular part. We are at this stage just simply producing the natural–what we think is the natural background signal against which the present-day signal should be compared to look at what new processes are occurring today that haven’t occurred in the past. That’s really–we’re basically setting just a framework for answering the sort of questions that you are asking now. But I can’t answer those at the moment.
PERIES: Yes. And do you think a gross reduction in greenhouse gas emissions will impact differently on the rising sea levels?
LAMBECK: I think the consequence of greenhouse gas emissions is probably much greater on the general climate, on the atmosphere system than on the sea level for most of this. Remember, the present-day rates of rise are on the order of a few millimeters per year and the history of sea level rise has shown that coastal environments generally can keep up with that. They can evolve in a way–they can adjust do this. For example, in a rising sea level environment, corals will grow upwards, and this should strengthen coral reefs, unless, of course, the temperatures or the ocean acidification gets such that corals die off. So those effects, I think, are likely to be more important than the actual rising sea levels.
PERIES: Right. And then, finally, to you, Professor Lambeck, is there a summary of your study available that we can put up on our site?
LAMBECK: You can use the abstract, I guess, from the PNAS article.
PERIES: Just for our audience, we will put a link to the study and the abstract up on our website under the interview.
Thank you so much for joining us, Professor Lambert.
LAMBECK: Thank you very much, Sharmini.
PERIES: And thank you for joining us on The Real News Network.
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