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A visual depiction of how much ice Greenland is losing

Posted on 27 April 2010 by John Cook

I'm talking at the University of Queensland next week so I thought I might use Skeptical Science to test-drive a new visual metaphor. Sometimes in the climate debate, we get a bit lost in the data and statistical analysis, forgetting the sheer scale of the impact we're having on our climate. A vivid example is the amount of ice that Greenland is currently losing. When scientists talk about ice loss from the Greenland ice sheet, they refer to gigatonnes of ice. One gigatonne is one billion tonnes. To get a picture of how large this is, imagine a block of ice one kilometre high by one kilometer wide by one kilometre deep (okay, the edges are actually 1055 metres long as ice is slightly less dense than water but you get the idea). Borrowing from alien invasion movies, the scale is well illustrated by comparing a gigatonne block of ice to a famous, historical landmark like the Empire State Building:

Empire State Building compared to 1 gigatonne of ice 

How much ice is Greenland losing? This is monitored by satellites which have measured changes in gravity around the ice sheet over the last decade (Velicogna 2009). In 2002 to 2003, the Greenland ice sheet was losing mass at a rate of 137 gigatonnes per year.

Empire State Building versus rate of ice loss from Greenland in 2002 to 2003 

However, the rate of ice loss has more than doubled in less than a decade. The rate of ice loss over the 2008 to 2009 period was 286 gigatonnes per year.

Empire State Building versus rate of ice mass loss from Greenland over 2008 to 2009 

This is a vivid reminder that global warming isn't a statistical abstraction cooked up in a climate lab. Greenland is just one example of the physical realities of climate change. On the other side of the planet, Antarctica is also losing ice at an accelerating rate. All over the globe, glaciers are retreating at an accelerating rate.

It's also a reminder of the massive amount of inertia at play in our climate. It takes time for the massive Greenland ice sheet to respond to warming. But this inertia is not our friend. Now that Greenland is losing ice at an accelerating rate, it's not like we can throw a rope around the ice sheet and hold it back. The steadily accelerating ice loss from Greenland is an ominous reminder that our actions now will have effects long into the future.

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Comments 51 to 88 out of 88:

  1. "The sea levels are going to do whatever Mother Nature wants them to do and we need to stop whining about it. " Um, why do you think sea level rises? Mother Nature suddenly makes more water? There is nothing we can do about tectonic subsidence but this is local. However, sea level rises or falls globally in response to temperature change. Do you seriously dispute that there is no credible scientific evidence to support this? And we surely can change the main forcing in temperature change (GHGs). And are you still insisting that no rate of change in temperature is not dangerous?
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  2. The Ville, (#40), As you say, the consequences of rising sea levels will be "huge". I got a feel for this issue while living in Rotterdam on a street 7 meters below mean sea level. Today I live in Florida, less than 5 meters above mean sea level. At the present rate it will take 1,000 years for the seas to rise 3 meters. If that rise happens, our distant ancestors will have plenty of time to move to higher ground.
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    Response: The key point is that sea level will not remain at the current rate - ice sheet melt is accelerating and past history tells us the ice sheets are very sensitive to sustained warmer temperatures. The latest peer-review analyses of future sea level rise, using various independent methods, predict sea level rise of 1 to 2 metres by 2100 (and don't forget that sea level rise will continue after 2100).
  3. Phila (#45), I can't prove that it is "impossible" to influence the rate of rise of sea levels. To the contrary, Mother Nature does it all the time, proving that it is possible. Can mankind control sea levels? I don't believe we can but I am open to persuasion if you can explain how to do it.
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  4. "Mother nature" is a very confusing term. Global sealevel responds to changes in temperature. I dont think you can postulate any other causes on time scale of million years or so. Do you seriously contest that temperature is NOT the cause of global sealevel temperatures? Since we are causing temperatures to rise thanks mainly to our GHG emissions, then of course we are influencing sea level.
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  5. scaddenp (#54), The world is in an "Ice Age" as we still have polar ice caps. Currently we are fortunate to be experiencing an "Interglacial" period characterised by relatively high temperatures. Over millennia, sustained high temperatures cause ice to melt and oceans to rise. Hopefully we are in agreement up to this point. When you say that we are causing temperatures to rise by generating GHGs I still agree with you. When it comes to quantifying humanity's contribution to the undeniable "Global Warming" that has occurred since 1850 we may diverge. While basic physics can show that a doubling of CO2 concentration should increase global temperatures by ~1.2 degrees Celsius, there is the question of feedback. Do other natural processes increase or diminish the effect of radiative forcing? Given the poor correlation of global temperature with CO2 concentration I consider it likely that natural effects are overwhelming the "Anthropogenic" influence.
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  6. Climate is not single-variable. Try the extremely strong correlation between temperature and all forcings. eg Benestad & Schmidt for an example of a statistical approach but the models are even better. The science has worked hard to estimate the size of all feedbacks and so far any globe-saving negative forcing has been extremely illusive. John Cook's summary on why GHG is the dominant forcing acting now is mighty good summary. If you have data to dispute this, then please post and continue the argument in the relevant place. So far this is a long way from your opening gambit that greenland's melting ice is a good thing.
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  7. scaddemp (#56), TOPEX is providing really accurate measurements. Currently the rate of sea level rise is averaging ~3.2 +/- 0.4 mm/year. The rate of rise is not showing any kind of "Hockey Stick" tendency that should be evident if sea levels are to rise by 1,900 mm (AR4 worst case) in the next 90 years (21 mm/year).
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  8. Nor does modelling expect there to be. What is expected is acceleration as ice melt gains pace, albedo reduces and sea temperature rise bring rain onto icecaps. Try looking at sealevel rise rates over last millennium, compared to this century, compared to last 50 years. More in is sealevel rise exaggerated? Are you prepared to admit by the way that a greenland ice melt that contributes to a 1m rise by end of century might actually be a problem?
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  9. gallopingcamel - your questions about future sea level rise predictions are better placed in sea level rise predictions
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  10. #52 gallopingcamel "Can mankind control sea levels? I don't believe we can but I am open to persuasion if you can explain how to do it." Echoing scaddenp (#51), if temperature can influence sea level, and GHGs can influence temperature, and human beings can influence GHG emissions, then it seems logical to say that human beings can influence sea level. For which of these propositions do you feel there is "no credible scientific evidence"?
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  11. scaddenp (#59), You will find that my numbers in (#57) are consistent with those in the link that you sent me. Look closely at "Figure 3" and you will see 1,900 mm of sea level rise by 2010. If the rate of sea level rise is going to increase by a factor of more than six during the 21st century, something dramatic needs to happen very soon. I don't disagree with your qualitative arguments; the problems appear when one tries to quantify them. Likewise, Phila (#60). Let us suppose that you could reduce the amount of CO2 in the atmosphere by a factor of 2 (to 194 ppm). This would be close to the concentration that will cause most plants to die but what would be the effect on sea levels?
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  12. @52 and GallopingCamel: "At the present rate it will take 1,000 years for the seas to rise 3 meters. If that rise happens, our distant ancestors will have plenty of time to move to higher ground." As pointed out, current rates will not be maintained. So the scenario is unlikely. But to clarify your point. Time is what most skeptics and deniers ignore. You yourself are proposing to ignore the problem because you believe it to be a distant problem. The result of such a stupid philosophy is that the infrastructures that are permanent will be expanded and in 1000 years from now, under your scenario they will have even bigger problems then if the same occurs in only 200 years. The longer you leave it, the bigger the problem gets. Your attitude is the problem, not the time scales or the science.
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  13. GallopingCamel said: "TOPEX is providing really accurate measurements. Currently the rate of sea level rise is averaging ~3.2 +/- 0.4 mm/year." The Ville: And those rates are changing and have been changing. Also the proportion attributed to thermal expansion and melting ice has changed over a relatively short period.
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  14. Gallopcamel said: "Can mankind control sea levels? I don't believe we can but I am open to persuasion if you can explain how to do it." The Ville: 1. I don't see why anyone is obliged to persuade you. 2. No one has suggested that they want to control sea levels directly, which is what you are implying. 3. The issue is the control of human influences on the environment that they inhabit. That we do have a responsibility for.
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  15. #15 Berényi Péter I would very much like to know the background for the 'LOL' in the editorial response to his graph: ''Response: LOL, can I ask what value you used for the total ice mass of the Greenland ice sheet and your source?'' As far as I can see his figures are correct (also noted by #22 CBDunkerson), and it would take 10000 years for the ice to completely melt at the present rate. Of course if we assume various kinds of increased ice loss rate, it will take less, but such assumptions are nothing more than assumptions based on a very small number of years. Why worry when we can do nothing about it anyway?
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    Response: The LOL wasn't meant to cast doubt on BP's graph - I just thought it was cool that he went to the trouble to track down the Greenland ice sheet total mass and draw a graph about it.
  16. Argus, explicit or not, there are always assumptions when talking about the future. Here comes the physics of climate, which we cannot ignore so easily.
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  17. Could we get some more info on you talking at UQ? Do you need to be a student to attend?
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    Response: Just got the final details myself - will add a post later today giving details. You don't need to be a student to attend.
  18. I think you should make all the gigaton blocks the same size visually. Your 1 gigaton looks the same size as half the second image.
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  19. Not that any of this is correct anyway, but... Argus, you are misquoting figures, the two commentators (Gallopingcamel and CBDunkerson) have quoted different figures. Gallopingcamel has refered to global sea levels which is linked to global ice melting, the inputs to that include thousands of glaciers, the Greenland ice sheet and Antartica. CBDunkerson has refered to just Greenland ice, which is a fraction of the input to global sea level rises and a fraction of the 3.2mm or so quoted by Gallopingcamel. If you are going to add anything. I suggest you actually pay attention to what your fellow skeptics write!
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  20. Oops sorry, I got the people mixed up in my last comment. Argus wasn't refering to Gallopingcamel, but to Berényi Péter.
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  21. #61 gallopingcamel "This would be close to the concentration that will cause most plants to die but what would be the effect on sea levels?" Going forward from this point, and considering no other effect than sea levels? I'd assume that seas would continue to rise, but without reaching the level or the rate of change that one would expect if CO2 remained at or above the current ppm. When I first addressed your comments, I understood you to be claiming that there's no evidence that human actions can influence the amount or rate of sea level rise. If your actual claim is that humans can't adjust sea levels precisely, whenever it pleases them to do so, then that's another debate entirely and quite frankly, I don't think it's a particularly relevant one. Regardless, I'm sorry if I misunderstood your argument. The important question, it seems to me, is whether limiting GHG emissions can reasonably be expected to limit the amount and rate of sea level rise (along with other serious problems). In other words, would we end up with higher sea levels and a faster rate of change at 600 ppm than at 385 ppm? That certainly seems to be what the science is telling us (see, for instance, Decline in Greenhouse Gas Emissions Would Reduce Sea-Level Rise, Save Arctic Sea Ice). The claim that "natural effects are overwhelming the 'Anthropogenic' influence" has been addressed in other threads (e.g., Climate's changed before; It's just a natural cycle; and Sea level rise is exaggerated).
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  22. @ #48 Chris oops. I used 10^-12 instead on 10^-9 in going from m^3 to km^3. Sorry. One nice feature of using river flows and lakes is that one can localize it. I couldn't find river flow data for any rivers in Australia, but for Lake Eyre(largest in Australia, I believe), I get 9500 km^2 (surface area) * .004 km(max depth) [both from Wikipedia] = 38 km^3 So the annual ice loss from Greenland (286 km^3) is about 7.5 times Lake Eyre. Another interesting comparison is with precipation. If we say the average annual precip for Australia is 500 mm (http://www.bom.gov.au/climate/change/rain.shtml) and the area of Australia is about 7.6 * 10^6 km, then 5.0*10^-4 * 7.6*10^6 = 3800 km^3 of water falls on all of Australia annually on average. So the annual Greenland ice loss of 286 km^3 is equivalent to just less than a month's rain over all of Australia (3800/12 = 316.7)... If my arithmetic is correct.
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  23. "if the rate of sea level rise is going to increase by a factor of more than six during the 21st century, something dramatic needs to happen very soon." Well for the actual calculations, see fig 3, Graph from Vermeer 2009
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  24. Phila (#61), That NSF paper you cited recommends holding CO2 concentrations to 450 ppm, something I could cheerfully accept if it can be done without destroying wealth on a large scale. Scaddenp (#73), Vermeer 2009 is fine as a piece of speculation but it has little relevance to the real world. For Vermeer's sea level rise of 1,790 mm by 2100 you would need a 6.1 degree Celsius rise in temperature as well.
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  25. gallopingcamel (#74) "That NSF paper you cited recommends holding CO2 concentrations to 450 ppm, something I could cheerfully accept if it can be done without destroying wealth on a large scale." Well, that's a whole other question. We could debate whether certain forecasts of wealth-destruction are "alarmist," but I don't think that's appropriate here. As far as the topic at hand goes, I'm glad we agree that human beings are capable of influencing sea level.
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  26. John you were going to post the details of the UQ talk.
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    Response: Sheesh, I'm still going through all the emails that came in overnight! :-) Will post within the hour.

    Are you Brisbane based? I'm picturing you devising a whopper of a question to ask me.
  27. "Vermeer 2009 is fine as a piece of speculation but it has little relevance to the real world." Sorry, which part of Vermeer is NOT based on real world data? What Vermeer cant do is predict what emissions we will actually produce, but as far as I can see from your postings, you are quite happy that we follow along the more unpleasant business-as-usual scenarios that is used. Since the models that predict have shown excellent predictive power so far why do you think they will suddenly stop working.
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  28. "Are you Brisbane based?" I wish, chilly Melbourne. Have a think about recording it and posting it here or Youtube.
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  29. gallopingcamel, you have veered off topic. Several commenters have pointed you to other threads on which your comments are relevant.
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  30. Phila (#71), your comment to #61-gallopingcamel : How could sea levels continue to rise if the amount of CO2 in the atmosphere was hypothetically reduced by a factor of 2 (to 194 ppm). If the CO2 content in the atmosphere is so essential for the increasing temperatures we observe (and the rising sea levels), I would rather expect the earth to rapidly cool off, and the sea levels to decrease as a consequence.
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  31. notcynical (#72), Applying localization and rainfall amounts, that's a neat 'trick'! I'm putting that in my bag for later use.
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  32. would be interesting to monitor the % of volume that Greenland and Antartica are losing on a yearly basis. Very vivid to show any acceleration.
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  33. @82 paulm % doesn't really do the job for the Antarctic at least. Most people have real difficulty with big numbers so you need to make it really really plain. 1% of Samoa is _not_ relevant in any meaningful way to 1% of China. Antarctica is the home of the unbelievably big number. If you wanted to use %s you'd be much better off comparing Antarctica ice losses to more familiar "units" like how many/much Sydney Harbours or Lake Superiors.
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  34. @80 argus Your expectations may be a bit unrealistic. My naive expectation would be that the best we could expect would be a reduction at much the same rate as the increase. But have a look at Tom Wigley's version for zero emissions by 2050. http://bravenewclimate.com/2010/11/24/effect-zero-co2-2050/
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  35. Re: adelady (83) "Lake Superiors" (outside my window as I type this) is a really useful comparative metric. I had once heard that the volume of water added to the atmosphere due to GW (4% increase) was equivalent to the volume of Lake Superior. When I did the math, I found that Lake Superior by itself roughly equaled the mass of the water in the entire atmospheric column. Wasn't a wasted exercise, though. I did find that the increase in water in the air was equivalent to the volume of Lake Erie (not that anyone would want to picture that raining down on them). If someone runs the numbers to get an ice volume equivalent for Lake Superior, I'd be interested in finding it out. The Yooper
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  36. #85: "the volume of Lake Erie (not that anyone would want to picture that raining down on them)" If methane keeps bubbling up as Arctic temperatures rise, it might start to look and smell like Lake Erie. Elliott 2010: Massive quantities of the greenhouse gas methane are stored beneath the Arctic continental shelf as clathrate hydrates, and the global warming signal is now reaching them. Over contemporary natural seeps, microbial activity tends to oxidize the molecule rapidly. Emissions driven by upcoming seafloor temperature rise, however, may be unprecedented in scale. Flux zones of dimension tens of kilometers are already under observation. Undersea landslides many times this size have been associated with catastrophic hydrate decomposition in the past. Yooper: My geology instruction centered around juggling rockhammers and consuming significant quantities of Labatt's Blue. Twenty-five years in the awl bidness later, I still can't juggle.
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  37. Re: muoncounter (86) Thanks, I guess, for the Elliott study. Been a bad week for climate news (lotsa news, all bad [prognosis: grim]).
    "Emissions driven by upcoming seafloor temperature rise, however, may be unprecedented in scale."
     Unprecedented? Nay, not unprecedented.
    "Multibeam swath bathymetry data from the southwest margin of the Chatham Rise, New Zealand, show gas release features over a region of at least 20,000 km2. Gas escape features, interpreted to be caused by gas hydrate dissociation, include an estimated a) 10 features, 8–11 km in diameter and b) 1,000 features, 1–5 km in diameter, both at 800–1,100 m water depth. An estimated 10,000 features, ∼150 m in diameter, are observed at 500–700 m water depth. If the methane from a single event at one 8–11 km scale pockmark reached the atmosphere, it would be equivalent to ∼3% of the current annual global methane released from natural sources into the atmosphere. If similar features formed globally, then the cumulative release may have significantly increased the global methane supply into the ocean and atmosphere at the peak of glaciations and potentially contributed to the rapid transition to warmer post‐glacial conditions (e.g. clathrate‐gun hypothesis [Kennett et al., 2003])."
     Aah, the wonders of Labatt's Blue. Palate has since shifted to first Blue Moon now to Oberon (all hail)... Between my science instructors and my history instructors (Oktoberfest was indeed a month-long affair to remember), it's a wonder that: 1. I learned anything 2. I still have a liver left Hmm, this topic brings to mind the scene in On The Beach (Gregory Peck 1959 version), where Fred Astaire says this line:
    “We’re all doomed, you know. The whole, silly, drunken, pathetic lot of us. Doomed by the air we’re about to breathe.”
     Of course, he was talking about radiation then, while'st we discuss the maudlin details of CO2 and CH4... How fitting that a movie line from over 50 years ago should serve as a lasting memorial for our race, should we not act on what we now know? The Yooper
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  38. Visualising the Greenland Ice Loss This is a rather late comment prompted by John Cook’s post on 16 April 2011. Because we live on a more or less flat surface, I have been thinking about the 286 billion tonnes lost in 2009 in terms of urban areas. With one tonne of fresh melt water at 4 degrees C having a volume of one cubic metre, the loss would sufficient to inundate an area 100 km x 100 km to a depth of 28.6 metres. It would flood the city of Brisbane (1636 sq. km) to a depth of 175 metres. It would flood the city of London (1610 sq. km) to a depth of 177 metres. It would flood the city of Los Angeles (1290 sq. km) to a depth of 222 metres. It would flood the city of New York (790 sq. km) to a depth of 362 metres. Finally, it would flood the city of Washington DC (177 sq. km) to a depth of 1,616 metres. That would fix those Republican skeptics!
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