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Saturday, January 19, 2008

Science: Climate Change Impact on Antarctica (Interview online of Eric Rignot and Marc Kaufman)

Marc Kaufman and Eric Rignot
Washington Post Staff Writer and NASA Scientist, respectively
Monday, January 14, 2008; 12:00 PM

Washington Post staff writer Marc Kaufman will be online at Noon ET on Monday, Jan. 14 to discuss the shrinking of the Antarctic ice sheet.
He will be joined by Eric Rignot, who has written a report in the scientific journal, Nature, that shows evidence that climactic changes may be destabilizing vast ice sheets of western Antarctica. Previously, this area of the continent was thought to be relatively protected from the impact of global warming.

As Kaufman, writes of Rignot's report, this raises the prospect of faster sea level rise than current estimates. Read more in Escalating Ice Loss Found in Antarctica (The Post, Jan. 14).

Rignot, a professor of earth system science at University of California, Irvine, is also a senior scientist with NASA's Jet Propulsion Laboratory.

A transcript follows.


Marc Kaufman: Good morning, and thanks for joining us. We also are fortunate to have Eric Rignot, author of the Nature study on Antarctica, on the chat, and he and I will do our best to answer your questions. Eric has studied Antarctica and Greenland for 15 years and is well known for his research. Before we start, a brief correction from me: Mt. Kilimanjaro is not, as I wrote, in Kenya, but in Tanzania.


Clarksville, Md.: The article today referenced Western Antarctica as on land, but also below sea level. Could you please explain this?

Eric Rignot: West Antarctica ice is grounded below sea level. But the top of the ice sheet is of course above sea level. Think about a vast expanse of ice sitting in the middle of the sea and reaching all the way down to the sea floor.

Clarksville, Md.: Using the best scientific common sense with data to date, what is the acceleration trend for the melting that you understand to be happening in Antarctica, and how does that translate into sea level rise by year or decade?

Eric Rignot: The actual trend in Antarctica is a contribution to sea level rise that increased from about 0.3 mm/yr in 1996 to 0.5 mm/yr in 2006. It was certainly lower prior to 1996, and will continue to increase in years to come.


Jefferson, N.C.: Sirs:

I have not seen Dr. Rignot's paper in NATURE, so my question may have already been answered.

For several years, there has been an indication that the temperatures over the Antarctic have cooled, as seen in the satellite data provided by MSU instruments as analyzed by UAH. This same data set was also analyzed by RSS and they chose to exclude any results poleward of 70S because of contamination due to the high elevations of interior Antarctica. Other researchers have reported that there is a warming trend seen in data collected near the coasts of Antarctica. In a paper published in the GRL, I found an apparent flaw in a comparison between sonde data and that produced by the UAH team (2003GL017938), perhaps another indication of surface contamination.

My question is, does the data in the NATURE paper support the claim that the Antarctic is warming and if so, how might that finding be reconciled with the cooling trend found by John Christy et al. at UAH?

R. E. Swanson

Eric Rignot: Good point. Antarctica's interior is cooling. The only air warming is in the Peninsula. But we are seeing at present in the glaciers is not related to atmospheric forcing. We think it is related to thermal forcing from the ocean. Changes in tropospheric circulation and wind patterns have enabled warm sources of water to reach glacier grounding lines and melt them from the bottom. This was the trigger for glacier acceleration in a large section of Antarctica.Melting of the frontal sections reduces the backforce on the glaciers and allows them to flow faster, much like what would happen if you slowly uncork a wine bottle .. or water bottle ..


Bowdoinham, Maine: If the western shelf is largely below sea level, please explain how melting could contribute to sea level rise.

Eric Rignot: The portion of West Antarctica which is below will contribute little to sea level change if it melts in the ocean; only the portion that is sitting above sea level will contribute in full. There is enough ice sitting above sea level however to raise total sea level by 5-6 m if West Antarctica were to melt to sea


Camden, Maine: It seems to me that the experts have consistently (almost) been too conservative in their estimates of coming changes in ice melt and other climatic changes.

Here's my question: Can't they somehow get the bigger picture and therefore predict with more accuracy? There are tons of inputs from all over the planet and taken collectively it would seem that even I, a simple lay person, can project that the future is going to be very, very exciting and challenging. I sometimes get the sense that the scientists are trying to downplay the obvious so as not to be too overbearing. Many did that in pre-Katrina times and look where it got us. I'd prefer to hear the unvarnished truth and have time to adjust and deal with it.

I'm working under the current assumption that climate change is going to be H-U-G-E and dealing with it is going where no man has gone before. Your thoughts?


Eric Rignot: Hello.

Prediction of what is going to happen in the polar regions is difficult. The existing models are not good enough. The first step in the last few years has been to get this accepted by the community, but this was tough. WE are now developing better models.

Scientists do not try to downplay. They have to go by the facts,by what they have, whether it is data or model results. We cannot make things up based on opinion. This is why we may at times sound too conservative.


College Park, Md.: I understand the data and the possible implications. I want to know how we also track our psychological and emotional responses to unprecedented change? What happens to researchers (and all of us) when the facts "enter your system", as Patchauri says?

Eric Rignot: As a scientist, I am trying to do the best research I can do and get objective views on changes in the polar regions. When talking to medias and the press or students about our results, however, I can present a more personal view, but it has to remain within the realms of what I know as a scientist.


New York City: How does the Antarctic ice sheets melt compare to the Greenland ice sheets...are they melting at the same rate?

Eric Rignot: Antarctic ice sheet loss is nearly comparable, though a bit smaller, than Greenland ice sheet loss. The rate of increase in the last ten years is also comparable.


Cary, N.C.: What is the source of the claim from global warming skeptics that Antarctic ice is growing, not shrinking, despite the collapse of the Larsen ice shelves?

Eric Rignot: Climate models have been predicting climate warming would increase precipitation in polar regions (because of enhanced evaporation on the oceans), which has indeed been the case in a few places (e.g. Antarctic Peninsula), but the effect is very modest. Since there is no melt in Antarctica and these models ignored the influence of glaciers, Antarctica could only grow. Reality shows otherwise. Reality shows that glaciers speed up and drive the ice sheet mass budget. This is a major shortcoming of models which we will now try to improve.

Models predicted a loss of Antarctic mass only after a warming of 4-5 degree Celsius. We are obviously there much sooner than expected.


Chantilly, Va.: In your own opinions, what can an average earth citizen do to help to slowdown the glacier melting process?

Eric Rignot: We need to appreciate the seriousness of the situation and the seriousness of climate change. We need to anticipate future changes in the best possible manner. I think that if there is a collective realization that this problem is truly important, we can make a big difference in our every day lives, and elect the right people to make the right decisions.


Toronto, Canada: Skeptics will be looking for holes in the climate change hypothesis. Please evaluate alternative explanations, such as ocean currents/temperature, or prevailing wind direction. Be a severe self-critic!

Eric Rignot: Antarctica has not been warming up. But climate change is complex and impacts many aspects of the climate system besides air temperatures. In the Antarctic, we believe that the main agent of change is the ocean and fluctuations in the sources of heat around the continent.


Fairfax County, Va.: Many of us, including me, base our knowledge of this issue on the movie An Inconvenient Truth, which was helpful to me because it offered a broad survey of the whole subject in lay terms. Do you think that movie gives an accurate picture (for a lay audience) of the scientific consensus on this subject? If it does, how does this new finding change what I learned from that film? Thank you for your work on this subject.

Eric Rignot: Inconvenient truth was an excellent movie because it was entirely based on scientific facts. I do not thin our new finding change much of what this film is showing, except that loss of antarctic ice is larger than thought at the time the movie was made.


New York, N.Y.: How similar or different on what is being observed in Antarctica being observed at the North Polar region?

Marc Kaufman: As I understand it, the sea ice of the Arctic is melting quickly in some areas, while until recently that was true only for the Antarctic peninsula. But a major difference is also that the sea ice in the Arctic typically does melt in the summer--with 5.8 million square miles winter sea ice that exist during winter shrinking on average to 2.7 sq miles in summer -- while that has not been the case typically in Antarctica. Also, much of the Arctic ice covers an ocean, while much of the Antarctic ice is on land in the form of glaciers, snow and ice sheets. Finally, most of the ice in the world is in the Antarctic.


Ojai, Calif.: When I saw Richard Alley at the AGU this December, he was quite concerned about global warming, but nonetheless said that the ice sheets would melt over the course of centuries, not decades. Does this study suggest otherwise?

Eric Rignot: ICe sheets will NOT melt in the course of decades, it will take centuries, there is no doubt about that. Yet some models have predicted it would take 1,000 years. What we are seeing today says it would happen over time scales of centuries. If sea level rises 1-2m in the next 100 years because of ice sheet melting, it would have a major impact on coastal populations.


Bowling Green, Ohio: A friend of mine says that "Global Warming" is occurring on other planets, specifically there is ice melt and that all the hoopla being caused by man is false. Any truth to this statement? Is global warming a cosmic occurrence that we have no control over?

-Dwight Taylor

Marc Kaufman: Climate changes are indeed common on other planets, and they have been on the Earth as well. But those natural warming processes occur over long time periods and seem to have different characteristics. But here are some factors that climate specialists--such as those in the Intergovernmental Panel on Climate Change--point to when they this is different. 1/ The build-up of carbon dioxide in the air has been dramatic and unprecedented. 2/ We now have glaciers in retreat not only in polar regions, but also in the high tropics -- the Andes, the Himalayas, and Mt. Kilimanjaro. 3/ Global average temperatures are quickly going up. Put it all together and you have a pretty dramatic picture. The scientists of the IPPC said that human activity was the primary cause, and they said it with a confidence level of 90 percent or so.


Silver Spring, Md.: A question for Eric or Marc...In the Post article this morning, "Rignot said there has been evidence of ice loss going back as far as 40 years", I assume you mean net ice loss? If so, what is the specific evidence?

Eric Rignot: Ice has been lost in the Antarctica Peninsula for several decades as a result of sustained climate warming. Climate warming in the Peninsula has been proceeding at 5 times the global average. But this is an anomaly, most of the rest of Antarctica remains cool. In the main area of Antarctica that is losing mass at present, however, we believe that warm pools of water are able to reach the glaciers as a result of changes in wind patterns. Some of these changes are traced back to the 1970s, but the mass loss numbers get smaller as we go back to the 1970s, so I think the change in ocean forcing started around that time. It turns out to be a time when observations suggest a shift in antarctic oscillation took place. But then the story becomes a bit too technical ...


Washington, D.C.: Could the wind pattern changes that are bringing more warm water to shore, and causing increased erosion of the glaciers and the ice sheets, be a result of the weather changes that are being caused by global dimming?

Eric Rignot: The change in wind patterns is related to global climate change. This is not my area of expertise, however, so I wont dwell into the details.

Climate models have (all) shown that climate change - while influenced by solar variability of course, as it always did in the past and will always do - was very strongly influence by greenhouse gases emissions. Climate models simply cannot match observations of climate change if they do not include human influence. This was a major conclusion of the last report from IPCC.


Raleigh, N.C.: Almost every day brings another article/more evidence about the damage human beings continue to inflict on the environment and the earth, and my despair and sadness deepens. Is there anything an "average" person can do to help in any significant way?

Marc Kaufman: Experts say that we can address the issue on both individual and societal levels. Individually we can try to reduce our use of gasoline, home heating oil and electricity, and try to learn more about how much energy goes into producing the products (including food) that we purchase. Based on that information, we can make more or less energy-efficient choices.

On a larger societal level, it is clear that many states and quite a few businesses have embraced reducing greenhouse gas emissions as a priority. Others have not, and perhaps they could be convinced over time. The big issue, of course, is the role of the federal government, with many saying the Bush administration has been missing in action. Bush officials say that is unfair, but whatever is the case, I think it's clear that his successor will have to do more. On this issue, I think that public pressure has shown itself to make a difference. The next step will be how to translate a desire to reduce global warming to an actual plan. For now, it certainly wouldn't hurt to plant some trees (which take up CO2.)


Olney, Md.: I'm curious about the theory that the "ice melt" or "ice recession" in Antarctica is being caused by warmer underwater currents. Has there been testing of the currents and have actual temperatures been measured? You didn't mention specific data in your story. How much warmer is this current? Thanks!

Eric Rignot: Unfortunately, we do not have much data to quantify how warm these currents are. In places where we do, however, the waters are 3 degrees warmer than 'normal' water. This is a very high temperature differential and quite possibly one of the warmest around Antarctica. Unsurprisingly, this also corresponds to the sector that is changing most rapidly at present.


Clarksville, Md.: Given what you know of Antarctic, Greenland, and global climate change, what can U.S. citizenry do to give you scientists better tools through government to develop the scientific evidence? Satellites, onsite monitoring stations, UAV's, etc.?

Eric Rignot: We need to make sure we have appropriate tools to observe ongoing changes. Unfortunately, the number of satellite missions flown to observe the Earth has been decreasing in the last decade, as a result of more efforts placed on the Mars program and the space station. I hope this will change. Studies have shown that if we were able to go back to the situation we were in the early 1990s, we would be ok.

Perhaps more important, we need better numerical models with the realization that existing ones have major shortcomings. Fortunately this can be solved by giving a job to a lot of smart young scientists interested in doing that.


Milwaukee, Wis.: Am I correct that the melting of ice in Antarctica is a more serious threat than in the Arctic in terms of ocean level rise because this ice is on land, like Greenland?

If you were looking ahead 50 years, would we be seeing by then many of our coastal cities beginning to be submerged, as well as flooded during storms and surges? And if this is the case, when will scientists begin telling the world that we must start planning, and soon to retreat from the coasts? This is going to take decades to prepare, but it seems we will only start dealing with it when we are in crisis mode.

Do scientists have the responsibility to urge these kinds of preparations?


Marc Kaufman: Yes, the loss of ice in Antarctica is the big issue in terms of ocean level rise. Some 90 percent of the world's ice is locked up in Antarctica, and that makes it the 900 pound gorilla. The large eastern section of the continent is on land and is not currently losing much ice -- indeed, some have found an increase in ice levels there. (Rignot's newest data shows a steady-state in terms of snowfall versus ice loss.) So for now, the drama is being played out in West Antarctica and the peninsula. The West Antarctic coast appears to be losing ice because of changed wind patterns and ocean movements that together bring more warm water from the circumpolar current to shore. The result is ice erosion and melting. But on the peninsula, the weather is also changing dramatically -- and is showing increased temperatures that are some of the most dramatic in the world. By the way, West Antarctica has as much ice as Greenland.


Washington, D.C.: Is there a relation between ocean temperature and sea level rise. In other words, how does just temperature change relate to increases in sea levels?

Marc Kaufman: The connection is that an increase in ocean temperatures has the effect of eroding glaciers and ice sheets. When they melt, that increases the volume of water in the oceans and so they rise. This is not an issue so much of sea ice, but rather of ice on land, or glaciers that have displaced ocean (as in West Antarctica.)


Clarksville, Md.: Sir, going back to your Camden, Maine, answer. I have to concur 100% with the questioner, but I also understand that scientifically-established truth has not caught up with the unraveling massive climate events. However, why can't the scientific community in this seemingly dire emergency for civilization, take what data they have, along with te 25-yr. history of scientific underestimates, and provide an un-scientific but extremely valuable "forecast" of where civilization is truly headed...without politicians having any say?

Eric Rignot: Good point. A lot of the changes we are observing today however have virtually no equivalent in the past. In the past, we did not have an outburst of greenhouse gases generated by an inhabitant of the planet. Also, despite all our accumulated knowledge of past climate, we do not know well how fast climate can change. Cores taken in Greenland in the early 1990s said: very fast, perhaps less than decades. New cores taken a few years ago said: even faster, perhaps years. This was unthinkable before these results were obtained.

In terms of ice sheets, we have been relatively data poor. It is hard to get there, get data over large areas, and measurements are difficult. Satellite remote sensing has truly changed our capability to understand what is happening the polar regions. But this only started a few decades ago, and as far as ice sheets are concerned, it really only started in the early 1990s. That's quite a short time to allow us to fully understand what is going and what the implications will be. But we will catch up. In March 2007, the International Polar Year started. There could not have been a better time for it.


Iowa City, Iowa: How many years have the glaciers been melting on Greenland? It would appear the comparison is not valid to the Antarctic regions. Please watch the film 90 Degree's South by Henry Ponting 1910 words added in 1933 to see some of the calving of icebergs 100 years ago. Can you explain Geologic Time against what you call real time today to help us all gain a little more understanding?

Eric Rignot: Greenland glaciers have been melting ever since the end of the last glacial maximum. It is an ongoing story. Except that the rate of melting at present is far larger than what it has been over the last century and there is no sign of it slowing down.

Similarly, Antarctica has been deglaciating since the last glacial maximum. In some parts of it, it is still ongoing, very slowly. In others, the deglaciation process is pretty much over.

Now this is a process over 100,000 years. What we are concerned about right now is the evolution of ice in the next 100 years.


Rockville, Md.: Given the rapid decrease of ice in the polar regions, how much longer are they saying it's going to be before Boston, NYC, other coastal cities are under water? I would think that would force us to do whatever it takes to stop global warming. Is it fair to say also, that if we plant millions of trees, that might help in stopping the warming?

Marc Kaufman: I think was has become clear over the past few years is that the global warming, and the related consequences, are taking place faster than expected. But that said, there are still so many imponderables involved that I don't think anyone has firm predictions about what will happen and when.

As for planting trees, it certainly couldn't hurt. I've seen studies suggesting that even massive tree planting in temperate climates would not make much difference in terms of global warming, but that it could have some effect on localized climates.


Clarksville, Md.: Sir, would you agree that the scientific community, through no fault of their own, have been disadvantaged over the past 25 years in trying to understand global climate change, but in attempting to address it, the scientific community has consistently underestimated the change rate and global dimensions? My understanding is that science cannot grasp the enormously complex and interdependent feedback loops in the warming trend...with new ones being discovered every few months. Your thoughts?

Eric Rignot: Yes, you are correct, but I am a bit more optimistic. I think the scientific community is coming to grasp with the Earth climate system. Slowly but surely. We are not doing very well in terms of predicting the future of ice sheets, but we are now gathering important information which will help improve the next generation of models. Global climate models were not doing very well 30 years ago. They came a long way and are now becoming more reliable. I remain optimistic that in years to come, not decades, we will produce more realistic predictions of the evolution of Greenland and Antarctica. We are learning tremendously right now about the dynamics of these systems. An unfortunate byproduct of changing the climate of the Earth so rapidly ...


Silver Spring, Md.: If Antarctic ice loss is accelerating - particularly in West Antarctica - as your work shows ... what do you think odds are it will collapse this century?

Eric Rignot: That is a very difficult question. I think a collapse of West Antarctica in the next 100-200 yr is now a concept that is back on the table; it was not on the table anymore 10 years ago; it was first put on the table in the early 1970s. But even if the ice sheet does not collapse, a loss of a significant portion of Antarctica and Greenland could raise sea level 1-2 m in the next century, and I think this is already something to worry about.


Milwaukee: Just want to reiterate the question: given how long a timeline would be needed, shouldn't scientists begin recommending development of a long-term plan for retreating from the coasts? Shouldn't there be some policy recommendations around the whole issue of coastal development that would be informed by this science -- not just here in the US, but also internationally? When does science interact with politics and economics -- neither or which is anywhere near catching up to the new alarms about melting ice sheets.

Marc Kaufman: I'm not sure it's up to scientists to come up with a long-term plan for pulling back from coastal areas -- that's far more a political, social and economic issue. The grim truth is that a huge proportion of human activity occurs within 100 miles of a coastline, and a large percentage of humans live in that region. So my guess is that nobody will do much until we are forced to by a number of tragedies like Katrina. There is just too much human and economic capital invested along coasts, and not enough certitude about the nature of the risk. But this said, it certainly seems to me that it's time for government to look seriously at limiting new development along coastal areas, and to do more about restoring coastal wetlands.


Normal trends versus altered trends: Just for the sake of clarity, can you explain briefly the difference between the normal global warming/cooling that we know has taken place from time to time and the influence of external factors including man-made issues that may increase or decrease these trends? I'm thinking in particular of things like magnetic polar shift as a normal trend compared to greenhouse gases that are clearly influenced by humanity.

Eric Rignot: This is a climate question. I am a glaciologist. From looking at ice melting, I cannot trace the origin of the change. I can only say: air temperatures have been getting warmer, or the ocean has been getting warmer, and the glacier changes we are observing are quite large compared to the background noise.

Ice sheets have growing and shrinking over time, over geologic times, over 100,000 year cycle. My view is that what we are witnessing right now is of a different nature. Ice sheets are responding to a spike in climate change created by us, and we are not well prepared to predict what may happen next. The only thing I can add to that is that this is serious problem. The way ice sheets are changing today, the rate at which they change worries me.


Clarksville, Md.: To Marc,

You & the Washington Post have done an excellent job of reporting global warming news over the past several years. I commend you! I hope that even as the Post has played a key role in national politics in the past in the name of truth, on the topic of awakening people everywhere to the coming global warming crises, the Post will take this subject where scientists cannot by their required discipline. As Dr. Rignot cited, there are not past parallel events to reference where we are. His dedication and that of his colleagues will be cited years hence as having saved many from disaster. Thank you!

Marc Kaufman: Many thanks for your comment. My colleagues Juliet Eilperin and Doug Struck have also written many stories on the subject, which clearly the paper sees as very important.

We thank you all for your questions, which have been most interesting and stimulating.


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