The Big Melt: Arctic Sea Ice At Record Low
August 30, 2012 1:26 p.m.
Ian Eisenman, Assistant Professor of Climate Science and physical oceanography at Scripps Institution of Oceanography, his research is on sea ice.
Related Story: The Big Melt: Arctic Sea Ice At Record Low
CAVANAUGH: Somewhere amidst the news this week about the Republican convention and hurricane Isaac, there was a les reported phenom that may end up being the digest news of all. Research scientists report that the level of arctic sea ice has reached a new recorded low. After a not particularly warm summer in the arctic, the region has lost more sea ice this year than in any time since records started in 1979. Climate scientists say this is all part of a cycle of fundamental climate change that is moving faster than expected. My guest, Ian Eisenman is scientist professor of climate science at Scripps institute of oceanography. Welcome to the show.
EISENMAN: Thanks a lot for having me on the show.
CAVANAUGH: News about this record ice melt is causing a great deal of reaction among scientists. Is this amount of loss surprising?
EISENMAN: In some ways, it is. We've seen a lot of ice lost during the observational record going back to 1979. In light of that loss, this is a little bit below of what might have been the best guess. At the same time we're not very good at predicting what it will be a year from now or a decade from now. This is well within the envelope of our uncertainty. But it's certainly a very dramatic loss that we're seeing this year.
CAVANAUGH: And if I'm not mistaken, this is not even the yearly low point of the melt; is that right?
EISENMAN: We still have more probably to come. So when we actually see the low point this year, it will probably be a bit lower than where it is now and quite a bit lower than what it's been at any record in the past. The lowest year was 2007.
CAVANAUGH: You mentioned that it's very difficult for climate scientists to predict what the ice loss might be or the amount of sea ice might be next year based on data that you get this year. Does it ebb and flow? I mean, is it low one year and a little bit higher the next?
EISENMAN: It is. There's a strong downward trend from one year to the next, if you look at what the summer minimum is in the arctic, there's a strong downward trend since 1979. But some years are a bit above that and some are below. 2007 was a low year, 2008 and 2009 had more ice. Certainly not what we had in the '80s, but compared to 2007, 2008 and 2009 were above 2007. And this year is very low.
CAVANAUGH: There's a vicious cycle to the loss of arctic sea ice and the warming of the planet. Could you tell us why the loss of arctic ice actually contributes to climate change?
EISENMAN: Yeah, so this cycle that you're referring to is the -- what people call the ice albedo feedback. Snow and ice are very reflective of sunlight. In contrast, the ocean absorbs sunlight, which is why it looked nearly black to the eye. Albedo is just a term for reflectiveness. So when sea ice melts, it exposes the ocean below. So an area that was white becomes black. In other words, more sunlight gets absorbed there, and this leads to further warming and more sea ice melt. So it's easy to imagine how this could lead to some sort of a runway effect. You warm the arctic a little bit, you cause a little bit of ice loss, it exposes some dark ocean, leading to more absorbed sunlight, more warming, more ice loss until the vicious cycle is done and all the ice is gone. One thing that's important to realize though is that this isn't the only player in the system. There's plenty of other physical factors influencing the arctic climate system, and a lot of them would stabilize the system and keep the ice from all melting away in response to just a modest warming. So there's been a lot of work recently on the question whether there will be some sort of a runaway feedback in the arctic. The term sometimes people use for this is a tipping point. As the ice cover diminishes, will there be a point in which we'll have a runway feedback effect that will just take off and remove all the remain ice? This is a topic I've worked on a fair amount myself. And in my view of it, the current evidence points to the idea we probably won't see a tipping point like this for the arctic sea ice in the foreseeable future. The other physical factors there stabilize the system and avoid this possibility of a runaway effect. But this is far from certain at this point. And it remains an active and intriguing topic of research in the community.
CAVANAUGH: Indeed, it is intriguing. I know that Scripps is one of the leading climate change research centers in the world. So you get this data that made the news this week from the NASA satellites, and they tell you how much the arctic sea ice -- the new low that's been reached. So what do you do when you get data like that? Do you revise your models? How do you use that?
EISENMAN: That's a very good question. I guess all different people in this field are coming at this from all different directions, but one of the major questions that guide us all relates to wanting to be able to predict the future. How much longer will we have a summertime sea ice cover in the arctic? Is it on its way out? That's done using climate models. So these are computer simulations, and they're -- they're really just based on the first principles of physicals, like Newton's second law. You code this all into a massive super computer. And in principle, these models aren't really -- you don't put the observations into them. You just put in the theory, the basic physics. But maybe the most basic test you can ask the models to do is to reproduce the observations. So I think at a time like this, it's an important time for people working with these models to be asking whether their models can produce something like what we're seeing.
CAVANAUGH: Then what does that mean? How could we get to where we are right now, and what does that mean for the future?
EISENMAN: Exactly, yeah. And the answer is pretty intriguing. The models that we have, there's a few dozen sort of state of the art global models of the atmosphere, ice, and ocean that are available in the international communication. And there's a lot of collaborative work. So a lot of people are looking at many or all of the models that come from all these different research centers. For the most part, they all think that we should lose a lot less ice than we do lose. They all underpredict the observed ice loss. So to the extent this is showing this one year added to the record, it shows that the long-term ice loss is even faster. So the models do a little worse now.
CAVANAUGH: I see.
EISENMAN: The two most obvious reasons for getting this wrong, the first is that there's something wrong in all of them, a systematic bias, and that's possible. The other models, they're trying to simulate what happens with the Greenhouse system in the atmosphere, how the climate responds. And the other possibility that what we're seeing in the arctic is partially the response to natural cycles and partially the response to climate change.
CAVANAUGH: When I was reading about this, that's what I read, that this newest idea is that it's sort of a bit of both, a natural cycle of warming that has just occurred on this planet over centuries, we just haven't been keeping track of it until somewhat recently. And then in addition to man-made climate change because of the greenhouse effect. And I'm wondering, how are you going to tell those two things apart?
EISENMAN: It's a really important question. Of and the natural warming doesn't have to be over centuries, it can be just over a few decades. We don't have very reliable records before the beginning of the current satellite observations in 1978. On a lot of people are looking for ways that the actually pattern of the ice retreat looks different in some ways, that it comes from natural variability than if it comes from part of global warming. It's still a pretty open question. And we're not at a point right now where we can answer with a lot of confidence.
CAVANAUGH: What might this say for the climate? You sound as if you're a deliberate scientist and you don't want to make claims that you can't support. But I have read that people who work in this discipline are concerned that a warmer arctic will slow down Rossby waves so that weather patterns get stuck for longer periods of time. Could you give us an explanation of what these Rossby waves are?
EISENMAN: Yeah, it's an interesting idea. And you have it exactly right. It's a paper that came out recently and got a fair amount of attention. For starters, these are basically atmospheric waves that are giant meanders in the high-latitude winds that move long from west to east in the northern mid-latitudes and are a major influence on our weather. So I guess one thing that's gotten people interested in this is that recently we have had some winters where we have had a warm arctic which diminished the ice cover. There's been cold and stormy weather in a lot of the northeastern U.S. and Europe. It might just be a coincidence, but there's been some speculation that maybe the two things are linked. So this study suggested that the arctic warming and associated sea ice loss would cause these Rossby waves in the upper atmosphere associated with the east to west progression of weather systems in northern mid-latitudes to slow down. So this would cause the storms then to move more slowly, get kind of stuck, and have an intensified local impact. At this point, I think the idea remains at the level of a speculative hypothesis. But it's an intriguing idea.
CAVANAUGH: To take it one more step, it might also mean extremes when it comes to droughts, when it comes to areas that get saturated, that get flooded. In other words the droughts, it's not just climate change bringing drier or wetter weather. It's that whatever is there might stay there longer.
EISENMAN: Exactly. So the weather systems getting stuck is sort of equivalent to an extreme weather event. If a snow storm and gets stuck over your city, it turns into an extreme snow storm just because it doesn't move on. That's the idea here. So this whole area of how extreme weather events might change in a warming climate I think is a really important topic right now that's really an active area of research, and it makes sense to look to the dramatic changes we're seeing in the arctic and ask how those would play into the picture.
CAVANAUGH: I want to go back to something you said, and that is a lot of the models that you have in research institutes across the world have predicted less loss of sea ice in the arctic than we've actually seen. I've also read after this new data showing this new low in the amount of summer sea ice in the arctic that the people who have been predicting a quicker loss of this ice, of this covering in the arctic are saying that these models do need to be changed in order to reflect that this is not something that's going to happen at the end of the 21st century. It may happen much, much sooner than that. Do you think it's too soon to make claims like that?
EISENMAN: I do. I think it's important to make the distinction that this research community and these models are really focused on questions of climate and not of weather, but of how 1 decade relates to another. There's a lot of variability that happens from day to day and from year to year in a given place you might live in the weather, which is a very different issue than whether a decade at the end of the coming century is going to be a lot warmer than the most recent decade. So I think we have to use a bit of restraint when we see one year that's noticeably different than another and ask questions about climate change. And keep in mind that these questions really are directed at a science that relates to how the climate system varies from 1 decade to another decade.
CAVANAUGH: When is it time to basically say this is real and this is happening?
EISENMAN: Well, I think that time is probably -- is well in the past. We have very good observations that the greenhouse force in the atmosphere has increased, and we have very good observations that the global mien temperature of the earth has increased in the past century, and the community has a very strong science now that it's very confident in that those two things are related, that we are seeing a very strong signal in the global temperature of human-induced climate change. So there are a lot of long records that we can look at and ask about climate, and I think this one additional year in the arctic sea ice record is an important thing to look at. And it is a point against the models, that they look like they're not simulating an arctic that's doing this. But I think it is important to look at it in the context of the decade and beyond.
CAVANAUGH: I want to thank you very much.
EISENMAN: Thank you very much for having me on the show. It was a real pleasure.