A major new study shows that Antarctica’s ice sheet is melting far faster than previously and than has been predicted, meaning that sea levels will rise faster than expected. We speak to the study’s lead author, Prof. Andrew Shepherd
Story Transcript
GREG WILPERT: It’s The Real News Network. I’m Greg Wilpert.
A new paper published in the journal Nature reveals alarming facts about the rate of ice melting in Antarctica, and how this accelerated rate contributes to rising sea levels. The title of the paper is “Mass balance of the Antarctic ice sheet from 1992-2017.” The research is a collaboration of several agencies that contribute to assessment reports of the Intergovernmental Panel on Climate Change, the IPCC. The IPCC is a group of thousands of scientists working on climate change under the auspices of the United Nations. The Antarctic ice sheet study found that the rate of Antarctic ice melt has tripled over the past five years, with more than 200 billion tons of ice flooding into oceans annually. And will contribute to at least six inches of sea level rise by 2100. Three trillion tons of ice have already disappeared from Antarctica since 1992.
The lead author of the report is Prof. Andrew Shepherd, and he is with us today to discuss the findings. Prof. Shepherd teaches and researches at Leeds University at the Institute for Climate and Atmospheric Science. He joins us today from Davos, Switzerland, at the moment. Welcome, Prof. Shepherd.
ANDREW SHEPHERD: Hi. Thanks for calling.
GREG WILPERT: So let’s start with how do the findings of your study differ from earlier studies on how human-caused climate change is increasing the rate of ice loss? Is Antarctic ice melting more quickly than expected?
ANDREW SHEPHERD: It is definitely melting faster than we expected. The last time we surveyed Antarctica five or six years ago it was losing ice, but at a fairly modest rate, and at a steady rate. And both those things are important. It was losing a small amount, much smaller than Greenland, and the amount it was losing was the same each year. Now we look at the ice sheet, and in the past five years it’s really clear now that actually the ice sheet is losing more ice each year, and that it’s crept up to an amount that’s quite substantial and makes us concerned about the future contribution.
GREG WILPERT: So what has changed? Do researchers know what is causing the rapid acceleration of ice melting in Antarctica? In your paper you talk about a tripling, or just now in your answer as well, of the ice melting the last five years. What factors have led to this acceleration according to, I mean, I don’t know if your study identified the factors, but according to what we know, what is leading to this acceleration?
ANDREW SHEPHERD: So we have lots of different satellites that we can use in space looking at earth today, and also going back in time. There were earlier missions in the 1990s and 2000s. And they each tell us different things. And so the pair of those measurements allows us to understand what the changes are and why they’re occurring. We see that in most of Antarctica, East Antarctica, the biggest part of the continent, there are very few changes. But in West Antarctica, which holds enough ice to raise sea levels by around four metres, the glaciers are flowing more quickly into the sea. And that’s because the ocean is melting the glaciers as they hit the ocean. The water is too warm for them to withstand. And it’s causing them to melt away and to retreat, and eventually pour more ice into the oceans.
GREG WILPERT: So your study says that Antarctica will contribute to six inches, will contribute six inches, or fifteen centimeters, to global sea level rise by 2100. How would a six-inch rise in the sea level impact coastal communities, weather patterns, and food systems?
ANDREW SHEPHERD: Those estimates of future sea level rise are IPCC scenarios. We have measurements for the past 25 years, and taking the first 20 years of measurements, as we did last time round, people thought that Antarctica was following a low trajectory for sea level rise, so the lowest range of the IPCC model scenarios. But in fact we were fooled a little bit, because there was a period in, around 2005, when a lot of snow fell on Antarctica and hid some of the ice losses that were happening at that time.
And the ice sheet is now following, and has been following, the upper trajectory for sea level rise that the IPCC made. The difference between those is about 15 centimetres across the planet on average. That may, that changes depending on which hemisphere you’re in. Ice loss in Antarctica cause sea levels to rise in the northern hemisphere more than in the southern hemisphere because of the way that gravity balances out the load and the sea level. So in the northern hemisphere we should expect more than 15 centimeters if the ice losses continue as they are today. And that does cause people to think about the frequency of flooding in a different way to we do today.
ANDREW SHEPHERD: But so, I mean, what more can you tell us exactly about the weather patterns. I mean, will this affect, also, weather patterns in some way?
ANDREW SHEPHERD: So when when the ice melts into the oceans, it causes them to rise. That’s an easy thing to understand. But they also cause them to freshen, as well, because it is freshwater, and the oceans are salt water. So the more ice that we put into the oceans, the fresher they become. And that does change patterns of ocean circulation, and we do know that the ocean circulates earth’s heat from the poles to the equator and back again. And so in the longer term, we will expect some disruption to weather patterns. But right now, our interesting weather is because of the way that cities flood.
Sea level rise tends to be thought of about the impacts on islands, and those islands becoming inundated. But in fact, the biggest infrastructure disruption will be for coastal cities during winter storms that occur at the same time as high tide conditions. And so the weather is a real factor in how frequently we should expect flooding. Right now it’s rare. Floods happen in major cities once every year, or two or three years. But if we raise sea levels by tens of centimetres the frequency will go up. And that’s why city planners want to know how high they need to build flood defences over the next 50 years.
GREG WILPERT: Let me turn to other factors that contribute to sea level rise. I mean, what other additional factors are there besides the melting of the ice? I remember, for example, that of course, obviously the Arctic region there’s also, you know, Greenland ice shelf is melting. But what other factors can you mention that contribute to the sea level rise?
ANDREW SHEPHERD: So the best estimates for sea level rise in the next century are in the range 40-60 centimeters. Half of that is expected to come from just the expansion of the oceans. So the water that’s already there, if we raise its temperature, it will expand a little bit, and that causes sea levels to effectively rise. And then we have a few other sources, melting of Greenland, that used to be thought of as the main concern for sea level rise over the next century. That’s no longer the case. We think that Antarctica could easily take over. Then there are mountain glaciers, and they’re different to the two polar ice sheets. They’re melting away. They make a contribution. And then there’s changes in the storage of water on land, and how much of that we put back into the oceans.
And when people make sea level projections for the next century they take into account changes, or expected changes, in all of those factors. Most of them are quite easy to simulate, because it’s not a very complicated problem to understand things like how mountain glaciers will melt. They respond pretty easily to changes in temperature, and so does Greenland. We can simulate how much water will get used on land, and we certainly know how to simulate how much the oceans themselves will expand. The biggest uncertainty in sea level rise is Antarctica. And it has always been the case, and we now think that the predictions are on the low side.
GREG WILPERT: Now, given what your research has found, would you say that a tipping point has reached in human-caused climate change, a point of no return where no amount of cutting of emissions can save Antarctica from melting? Or if we haven’t reached a tipping point yet, how far are we from reaching it?
ANDREW SHEPHERD: So what we know about the glaciers that are causing the problem in Antarctica today is that their increased ice losses could be reversed if ocean temperatures cooled. And that’s not an irreversible process. The question is whether or not the ocean temperature can be cooled. And that’s a, that’s more than just a scientific problem, because it depends upon policy decisions that governments will make, and also innovation in technology, which we all hope will save us a little bit from climate change. And we can’t predict many of those things, how they will change.
But I don’t know that many people expect the ocean temperatures to cool anytime soon, and so we have to, perhaps, adapt and expect some sea level rise. And the sooner people believe that the sea level rise will come, irrespective of what caused the changes in the first instance, so you mentioned climate change, but we don’t need to. We know that Antarctica is going to continue to give its ice to the oceans and cause sea levels to rise, and people should trust us on that, and then start asking their politicians what they’re going to do about it.
GREG WILPERT: Then finally, what do you think-. And this is actually turning also, I guess, to the policy issue. What can and should be done in light of this new information? And does this mean, for example, that the goals set by the Paris agreements cannot be met the way they are set, that they need to be adjusted?
ANDREW SHEPHERD: Again, the Paris agreement is a completely different issue to the one that we’re reporting today. And that is that irrespective of changes in policy decisions, we should expect some sea level rise. And I think it’s best work on the assumption that if things stay as they are today, the sea level rise will come. And on that basis, every coastal city should have a very clear and transparent, and actually broadcast to the citizens, coastal flood protection policy and what they’re going to do in the next 50 years. If you want to raise San Francisco’s or Vancouver’s riverfront by 50 or 100 centimeters, that’s going to require some thought. It’s not, it’s not by any stretch of the imagination impossible to do. It can be done. But none of those cities will want a wall around their coastlines, because this is a major attraction, and iss also for the residents a beautiful thing.
So yeah, you’ll need to think again, and think about raising the roads, and issues like that. And so this causes disruption and money, and they should be fully costed plans. And people should see those plans, and the policy makers and town planners should present them now.
GREG WILPERT: OK. Well, we’ll definitely continue to follow this as we always do. I was speaking to Prof. Andrew Shepherd of the Leeds University Institute for Climate and Atmospheric Science. Thanks again, Prof. Shepherd, for having joined us today.
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