Air Date: Week of May 11, 2007
The scientists' models were averaged into a single line (red) to provide a comparison to their observations. (Photo: National Snow and Ice Data Center)
A new study from the National Snow and Ice Data Center in Boulder, Colorado shows that scientists grossly underestimated the rate of ice loss due to warming from greenhouse gas emissions. The study claims that if current trends continue, we could be facing an ice-free Arctic summer within the next 50 years.
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CURWOOD: From the Jennifer and Ted Stanley Studios in Somerville, Massachusetts - this is Living on Earth. I’m Steve Curwood.
Humans are disrupting the climate faster than just about anyone has been predicting. That’s the conclusion of a new study of the Arctic Polar ice cap recently published in the journal Geophysical Research Letters. The study finds that the ice cap over the Arctic Ocean is melting far faster than even the most pessimistic computer models have been predicting. And it follows similar findings about the rapid meltdown of the Greenland ice sheet. Mark Serreze is a senior research scientist at the National Snow and Ice Data Center in Boulder, Colorado which conducted the study. Thanks for being here, Mark.
SERREZE: Oh, it’s my pleasure.
CURWOOD: So what’s the big difference between the computer models that are cited by the Intergovernmental Panel on Climate Change in their most recent assessment and the data that your team has been looking at?
SERREZE: Basically all of these climate models are saying that we should be loosing sea ice. So there’s this consensus between all of the different climate models regarding this loss. And this is very very strong evidence that we’re starting to see the impact of green house warming. But when we actually look at the data; our data records from satellites and other sources we find that the observed rate of decline is roughly almost three times that what the models are projecting. What it’s telling us is that these models are underestimating the loss. They’re not quick enough. It’s telling us that this loss of sea ice is rapid and the arctic is on this fast track of change.
SERREZE: Well, it’s not quite clear. It may be that the models are missing some of the key processes: feedbacks. In the arctic one of the things that is at work there is what we call the albedo feedback. Albedo is just a fancy word for the reflectivity or whiteness of that surface. The idea here is that if we have some warming that melts some of this highly reflective snow and ice surface and that starts to expose darker areas of ocean underneath. That means that those darker ocean areas now absorb more of the sun’s heat. That causes further melting, further warming and further melting and so on. So, it’s a vicious cycle if you will. Well all of these climate models are supposed to treat those sorts of processes but it may be that they’re not quite getting them right.
CURWOOD: Now of course sea ice won’t affect sea level around the world. It’s already floating on the ocean.
SERREZE: That’s correct, Archimedes Principle.
CURWOOD: But what are the possible impacts of the loss of arctic ice for the rest of the world?
SERREZE: Well, there’s one recent study suggesting that one impact could be an extended drought in the US West. Ok, in other words we have a shift in atmospheric circulation associated with this changing arctic refrigerator and one response of that was drought in the Western US. Other studies were pointing towards some rather pronounced changes in patterns of precipitation or weather in Europe. Ok, so those are just a few examples. The problem here is that getting at these particular regional impacts is still very difficult in these models. That changes will occur seems to be quite clear. Just how they will pan out, that’s what’s difficult to get at. And these are the things that concern me. It’s not so much what we know that worries me. It’s what we don’t know.
CURWOOD: In many ways nature doesn’t move in a smooth line to change. It has quantum leaps. Whether it is the flower that’s closed one day and open the next or an electron that’s in one orbital around the nucleus of an atom and then when the energy level changes it’s in another. To what extent does your research suggest that climate shift may be more of a quantum nature, may be making more of a leap than making a smooth transition?
SERREZE: Well, that’s exactly what I think we are probably seeing now. When we think of the arctic we often think of this idea of tipping point. That say if we thin that sea ice down to a fairly vulnerable state a little kick to the system can send it over the edge and send it very quickly into a new state. We see evidence for that in terms of the sea ice cover. Another example is what we’re seeing with respect to the Greenland ice sheet. We’d always thought that the Greenland ice sheet would slowly melt down and slowly contribute to sea level rise. But what we’re seeing now is that that’s not the case. For example what we’re seeing there is that there’s surface melt going on.
This melt water is trickling down to the bottom of these immense glaciers that drain the ice sheet, literally lubricating the glaciers and so now they can slide more easily into the Arctic Ocean. We didn’t think that that sort of thing would happen so quickly but it is. And we see the same analogous sort of things in the sea ice cover. What these records show is that the climate system can jump up and bite you very hard and very quickly. And there’s growing concern that as we continue to load the atmosphere with greenhouse gasses we may set ourselves up for a tipping point. We may set ourselves up for one of these rapid changes.
CURWOOD: Well thank you Dr. Serreze.
SERREZE: It’s been my pleasure.
CURWOOD: Mark Serreze is a Senior Research Scientist_ at the National Snow and Ice Data Center, and a coauthor of a new report on the melt down of Arctic ice. You can find out more on our website, LOE dot org.
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