Dueling press releases on ice melt – one says ‘uncertainty is large’ the other quantifies a number

Once again, it looks like claims of ‘consensus’ are overblown. In our previous news item we have this:

…ice sheets are the largest potential source of future sea level rise – and they also possess the largest uncertainty over their future behaviour.

and

Yet, there is no consensus among scientists about the cause of this recent increase in ice sheet mass loss observed by satellites. Beside anthropogenic warming, ice sheets are affected by many natural processes…

Yet these folks at the Potsdam Institute for Climate Impact Research are certain they have the numbers dialed in. No matter who you believe, clearly there’s no consensus. Which one do you think will get the headlines? I’m betting Potsdam due to the “if it bleeds it leads” nature of their press release.

Each degree of global warming might ultimately raise global sea levels by more than 2 meters

07/15/2013 – Greenhouse gases emitted today will cause sea level to rise for centuries to come. Each degree of global warming is likely to raise sea level by more than 2 meters in the future, a study now published in the Proceedings of the National Academy of Sciences shows. While thermal expansion of the ocean and melting mountain glaciers are the most important factors causing sea-level change today, the Greenland and Antarctic ice sheets will be the dominant contributors within the next two millennia, according to the findings. Half of that rise might come from ice-loss in Antarctica which is currently contributing less than 10 percent to global sea-level rise.

“CO2, once emitted by burning fossil fuels, stays an awful long time in the atmosphere,” says Anders Levermann, lead author of the study and research domain co-chair at the Potsdam Institute for Climate Impact Research. “Consequently, the warming it causes also persists.” The oceans and ice sheets are slow in responding, simply because of their enormous mass, which is why observed sea-level rise is now measured in millimeters per year. “The problem is: once heated out of balance, they simply don’t stop,” says Levermann. “We’re confident that our estimate is robust because of the combination of physics and data that we use.”

The study is the first to combine evidence from early Earth’s climate history with comprehensive computer simulations using physical models of all four major contributors to long-term global sea-level rise. During the 20th century, sea level rose by about 0.2 meters, and it is projected to rise by significantly less than two meters by 2100 even for the strongest scenarios considered. At the same time, past climate records, which average sea-level and temperature changes over a long time, suggest much higher sea levels during periods of Earth history that were warmer than present.

For the study now published, the international team of scientists used data from sediments from the bottom of the sea and ancient raised shorelines found on various coastlines around the world. All the models are based on fundamental physical laws. “The Antarctic computer simulations were able to simulate the past five million years of ice history, and the other two ice models were directly calibrated against observational data – which in combination makes the scientists confident that these models are correctly estimating the future evolution of long-term sea-level rise,” says Peter Clark, a paleo-climatologist at Oregon State University and co-author on the study. While it remains a challenge to simulate rapid ice-loss from Greenland and Antarctica, the models are able to capture ice loss that occurs on long time scales where a lot of the small rapid motion averages out.

If global mean temperature rises by 4 degrees compared to pre-industrial times, which in a business-as-usual scenario is projected to happen within less than a century, the Antarctic ice sheet will contribute about 50 percent of sea-level rise over the next two millennia. Greenland will add another 25 percent to the total sea-level rise, while the thermal expansion of the oceans’ water, currently the largest component of sea-level rise, will contribute about 20 percent, and the contribution from mountain glaciers will decline to less than 5 percent, mostly because many of them will shrink to a minimum.

“Continuous sea-level rise is something we cannot avoid unless global temperatures go down again,” concludes Levermann. “Thus we can be absolutely certain that we need to adapt. Sea-level rise might be slow on time scales on which we elect governments, but it is inevitable and therefore highly relevant for almost everything we build along our coastlines, for many generations to come.”

Article: Levermann, A., Clark, P., Marzeion, B., Milne, G., Pollard, D., Radic, V., Robinson, A. (2013): The multimillennial sea-level commitment of global warming. Proceedings of the National Academy of Sciences (early online edition) [DOI: 10.1073/pnas.1219414110 ]

Weblink to the article once it is published: www.pnas.org/cgi/doi/10.1073/pnas.1219414110

Weblink to the article in open access once it is published: http://www.pnas.org/content/early/recent

Source or press release: http://www.pik-potsdam.de/news/press-releases/jedes-grad-erderwaermung-koennte-den-meeresspiegel-auf-lange-sicht-um-mehr-als-2-meter-erhoehen

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43 thoughts on “Dueling press releases on ice melt – one says ‘uncertainty is large’ the other quantifies a number

  1. We’re confident that our estimate is robust because of the combination of physics and data that we use.

    Oh. Well in that case. Since you’ve used a combination of physics and data, I guess that settles it.
    I mean, really? What the heck sort of statement is that? Usually when people talk about confidence and robustness there is some mention of uncertainties and confidence intervals instead of a flat assertation that the result is robust because ‘we used a combination of physics and data’…

  2. “We’re confident that our estimate is robust because of the combination of physics and data that we use.”

    It makes a pleasant change for the alarmists to actually use any physics or real empirical data, at all, so using both is a vast improvement….

    Although that does not mean that they used them properly.

  3. OT but I think Google has found a way to post skeptic stories but about a month late. On the other hand, AGW stories are published immediately. If you type “global warming scam” ect, in Google News, most of the stories are weeks or months old. If you type “global warming” all the recent alarmist stories are there.

  4. “CO2, once emitted by burning fossil fuels, stays an awful long time in the atmosphere,”

    Go back, start over.

  5. You should realise that the patients at the Potsdam Institute for Climate Impact Research Asylum have taken over their daily climastrology rantings.

  6. Statement, corrected:

    “We’re confident that our estimate is robust because we have changed the definition of “robust” to mean anything we want it to mean at any particular moment.”

  7. “Half of that rise might come from ice-loss in Antarctica which is currently contributing less than 10 percent to global sea-level rise.”

    I thought the ice extent for Antarctica is near its record for the satellite era. Where did the nearly 10 percent come from? The extent is near record but the volume is substantially reduced?

  8. To be clear – one side says there is no consensus, and the other side says there is a consensus.

    Is there a meta-consensus on whether or not the consensus side is correct, or is it the non-consensus side that has the consensus?

  9. Antarctica which is currently contributing less than 10 percent to global sea-level rise.

    Weasel words again – “less than 10 percent” obviously includes -ve contributions to sea level rise, so is technically true, but …..

  10. “Continuous sea-level rise is something we cannot avoid unless global temperatures go down again,”

    Beautifull! Now we know that things will get worse, unless they get better.

  11. Ultmate rise prediction is 2 meters/degree rise and ultimate is 2,000 years? Do these guys ever have it dialed in. So, we’d get 8 meters for the 4°C by 4013. I wonder if that comes with a money back guarantee?

  12. More dueling…………at Reuters. The consensus is crumbling before our very eyes. 2013, after Climategate, is their second Annus horribilis.

    Winds of change are blowing through Reuters’ environmental coverage…….The result of the reported row was Stott’s abrupt dismissal after a 25-year, high-profile career with Reuters. The two editors had differed previously about a global warming story………..

    http://tomnelson.blogspot.com/2013/07/don-miss-this-from-climate-skeptics-is.html

  13. “The oceans and ice sheets are slow in responding, simply because of their enormous mass,…”

    If there is such inertia how come the poles lose between 60% and 70% every year?

  14. Let’s see, over the last hundred years, we’ve had a temperature increase of about 1 deg. C and sea level has risen … 7 inches. I wonder how their model explains that?

  15. @ dave, July 16, 2013 at 10:11 am

    You are confusing sea ice (typically a few meters thick floating in the oceans) with ice sheets (typically a few km thick resting on land). Floating sea ice will have minimal impacts on sea level. Land-based ice sheets can have a large impact if the H2O flows off into the ocean.

  16. The study is the first to combine evidence from early Earth’s climate history with comprehensive computer simulations using physical models of all four major contributors to long-term global sea-level rise. During the 20th century, sea level rose by about 0.2 meters, and it is projected to rise by significantly less than two meters by 2100 even for the strongest scenarios considered. At the same time, past climate records, which average sea-level and temperature changes over a long time, suggest much higher sea levels during periods of Earth history that were warmer than present.

    An interesting historical fact. Amsterdam – which is not known for its towering height above sea level – was founded as a fishing village at the edge of the sea at the height of the Medieval Warm Period when Vikings were farming areas of Greenland that is currently permafrost. Temperatures were obviously significantly higher in Greenland for a few <centuries yet Amsterdam has remained on the edge of the sea at sea level since its founding in the late 12th century. History shows that at no time did the sea leave Amsterdam high and dry, and now when it is warm again Amsterdam is still in existence on the coast as a major port.

    Perhaps the “comprehensive computer simulations” need different tuning parameters?

  17. Okay, just a few things:
    “The problem is: once heated out of balance, they simply don’t stop,” says Levermann.
    Heated out of balance?!

    “The study is the first to combine evidence from early Earth’s climate history with comprehensive computer simulations using physical models of all four major contributors to long-term global sea-level rise.”
    Let’s see, I guess that’s CO2, CO2, CO2 & CO2?

    “…and the other two ice models were directly calibrated against observational data – which in combination makes the scientists confident that these models are correctly estimating the future evolution of long-term sea-level rise…”
    Directly calibrated against observational data? Do they mean all 11 years worth of satellite data from GRACE?
    How terribly impressive.

  18. Hansen predicted over 20 years ago that parts of New York City would be under water now. He had that dialed in too!

  19. “CO2, once emitted by burning fossil fuels, stays an awful long time in the atmosphere,”

    Wow. Does the author mean the ~3% of the total CO2 emitted into the atmosphere each year? And—exactly what are the physical properties that make CO2 from fossil fuels differ from CO2 from natural sources?

    The world—and science—want to know.

  20. Ian W says:
    July 16, 2013 at 10:59 am
    .. yet Amsterdam has remained on the edge of the sea at sea level since its founding …
    … History shows that at no time did the sea leave Amsterdam high and dry, …
    ========================================================
    Amsterdam has been connected to the North Sea by the Noordzeekanaal since the mid 19th century. It’s about 25km long.

  21. Thus we can be absolutely certain that we need to adapt. Sea-level rise might be slow on time scales on which we elect governments, but it is inevitable and therefore highly relevant for almost everything we build along our coastlines, for many generations to come.

    Of course they do not know that sea-level rise is inevitable. But whether it rises, falls, or stays the same makes little difference to the developments now along coastlines. A nice firm surge from a moderately intense storm during a high tide ought to be of immediate concern. About 40% (?) of the area of Detroit is open for resettlement. A few hundred thousand folks could move off the sand and sediment, re-populate Detroit, and solve two major issues faced by the USA. Not building new housing and related structures along coastlines does have a nice common sense sound to it.

  22. View from the Solent says:
    July 16, 2013 at 11:33 am

    Ian W says:
    July 16, 2013 at 10:59 am
    .. yet Amsterdam has remained on the edge of the sea at sea level since its founding …
    … History shows that at no time did the sea leave Amsterdam high and dry, …
    ========================================================
    Amsterdam has been connected to the North Sea by the Noordzeekanaal since the mid 19th century. It’s about 25km long.

    And how many rising locks are there on the Noordzeekanaal?

  23. Eliza says:
    July 16, 2013 at 9:46 am
    “OT but I think Google has found a way to post skeptic stories but about a month late. On the other hand, AGW stories are published immediately. If you type “global warming scam” ect, in Google News, most of the stories are weeks or months old. If you type “global warming” all the recent alarmist stories are there.”

    No. Global Warming Scam is simply a longer phrase and therefore less likely to be used at any given time. Google attempts to give precise matches first, and as usage of the phrase is much rarer than Global Warming alone you get matches that are on average older. Larry & Sergej and Eric may be cynical liberal top dogs but nobody including the NSA gives a fart for the phrase “Global Warming Scam”.

  24. Reading WUWT, often and avidly, leaving not much time for other Internet pursuits I just change ‘Potsdam’ to ‘Mental’ and move on.

  25. If this latest science is accurate, it looks to be a huge walkback from alarmism, although the PR remains disguised as alarmism.

    Here’s why:

    The Reuters story on this study correctly notes that “Some scientific studies have projected sea level rise of up to 2 meters by 2100, a figure that would swamp large tracts of land from Bangladesh to Florida.” Here is the link to Reuters:

    http://www.chicagotribune.com/business/sns-rt-us-climate-ice-study-20130715,0,656577.story

    Got that? Up to 6 feet (almost 2 meters) in less than one hundred years. That is standard alarmism.

    This present study says that the 6 feet will take not 87 years, not 100 years, but 2 millennia, 2000 years. Meaning that the rate of warming has just dropped by as much as a factor of 20.

    Put another way, if the world were somehow to maintain a one degree increase for 20 centuries — surely something that wouldn’t happen if warming turns out to be truly problematic — then sea levels over those 20 centuries would rise 2 meters, call it 80 inches.

    Now divide by 20. That is a rate of 4 inches per century.

    Hope everyone is chilling out now.

    Also note that this rate of sea level rise is pretty close to the new articles on Greenland’s ice melt, which also show far less sea level rise than the standard alarmism when the science was less complete and allowed more scope for alarmism:

    http://wattsupwiththat.com/2013/07/03/great-news-from-greenland/

    http://wattsupwiththat.com/2013/01/24/first-complete-ice-core-record-of-last-interglacial-period-shows-the-climate-of-greenland-to-be-significantly-warmer-than-today/

    One final note. Sea level rise is currently at about 3.2 millimeters per year, or about a foot a century. That is 3 X higher than 4 inches per century. One reason is that fast increasing amounts of irrigation with waters from deep aquifers adds to sea level rise when the water eventually reaches the oceans. The article below reviews two papers. One finds that 0.57 millimaters per year were added to sea level rise in 2000 due to bringing pre-historical waters from underground to the surface. The other says that from 1961 through 2003, irrigation added 0.77 millimeters per year to sea level rise. See:

    http://www.nature.com/news/source-found-for-missing-water-in-sea-level-rise-1.10676

    Other articles I’ve read suggest whatever the rate in 2003, this rate has now increased.

  26. Pity they didn’t also correlate their estimates of co2 rise with past levels of co2 while they at it. But then they would not have been able to justify their conclusions and get further funding.

  27. How can the Antarctic icecap, (not sea ice) be melting when temperatures in Antarctica have been trending down.
    Not to mention again the sea ice extending further and further out.

  28. In the previous post on melting ice there was this really scary figure of a net 300 billion tonnes of ice melting annually. If you do the maths that is equivalent to the equally scary figure of 0.83mm/year or 83mm (or 3.26 inches) per century.

    There is no increase in the ocean temperatures below 700 metres and only a negligible amount above it. So thermal expansion of the ocean is mostly BS.

    The land temperature has stayed statistically static for around 16-18 years.

    We truly have to be scared, very very scared. No wonder the highly authoritive IPCC is forecasting sea levels to rise by 200-500mms over the next century, with the emphasis obviously on all 500mm+ estimates.

  29. two different answers, certain and uncertain, because of two different time scales. not that hard to understand

    REPLY: One is measurement based, the other is an educated guess, not that hard to understand. – Anthony

  30. Each degree of global warming might ultimately raise global sea levels by more than 2 meters

    Lets check:
    Atmosphere
    weight:5.148×10^21 g
    heat capacity: 1.0035 J/g/K
    energy needed to raise temperature 1K
    5.166×10^21 J

    Ocean surface layer 361132000 km^2, 200m depth, mean temperature 290 K
    weight: 7.41×10^22 g
    heat capacity 4.1813 J/g/K
    energy neded to raise temperature 1 K:
    3.0983×10^23 J

    Together 3.14996×10^23 J

    Ice (only icesheet, the seaice melt cannot raise the ocean sea level due to Archimedes principle)
    heat of fusion 334 J/g/K
    how much ice 3.14996×10^23 J melts?
    3.14996×10^23 g / 334 = 9.43×10^20 g = 9.43×10^14 m^2
    = 9.43×10^8 km^2 1m thick ocean surface / 3.61132×10^8 km^2 = 2.6 m would be the sea level rise in case all the heat used to the ice melt
    But this resulting 2.6 m zero C water would need to be warmed 18 C to the then mean sea surface temperature to reestablish equilibrium
    for heating
    361132000000000 x 2.6 = 9.3889×10^21 g water would be needed 9.3889×10^21 x 4.1813 = 3.926X10^22J
    3.0983×10^23 / 3.926×10^22 = 7.89
    2.6 m /7.89 = 0.33
    2.6 – 0.33 = 2.27 m
    So in ideal case all the heat would be used for ice melt, the sea level would rise 2.27 m for 1 K temperature rise.

    But how likely is all the ice to melt has zero C temperature?

    If not then for each centigrade below zero you must add 4.1813 to above 334 J/g/K figure.
    90%+ of the icesheet is Antarctica icesheet.
    The mean surface temperature in Antarctica is around minus 40C, so you would need to add
    0.9 x 4.1813 x 40 = 150 to the above 334 J/g/K figure and the result will be 1.6 m of ocean level rise in case all the heat will be used for ice melt when omiting the ice temperature in Arctica and Greenland.
    So even with oversimplified calculation and assumption all heat goes into the ice melt – which is highly unlikely – the resulting figure would be way under the 2 m per centigrade sea level rise they claim. So we can conclude the claim that one “degree of global warming might ultimately raise global sea levels by more than 2 meters” is false.

    Moreover when we go back to reality it is clear, that Antarctica seaice extent rises for decades and so is very likely also the Antarctica icesheet closer to pole experiences net increase.
    Therefore sea level rise due to Antarctica icesheet melt is in reality highly unlikely and I would bet all the ice melt at the northern hemisphere can’t offset the net gain in Antarctica.
    What remains is thermosteric sea level rise which surely isn’t “more than 2 meters” per one degree global warming. -Even if whole the ocean would be heated 1 C – which would require way more heat than for warming the surface layer – the sealevel would in result rise only 0.78 m.

  31. To Stephen Skinner:

    You wrote: “If there is such inertia how come the poles lose between 60% and 70% every year?”

    They don’t. You may be thinking of sea ice, which does vary quite a bit. However,
    the article is talking about the land-based ice sheets of Greenland and Antarctica.
    Those miles-deep ice sheets may be melting–Greenland probably is–but even
    a rate of 1000 Gt/year would take over 2500 years to melt the whole Greenland
    ice sheet. It’s not even clear that Antarctica is losing ice mass at all–see the
    paper last year: M. Frezzotti et al.: Antarctic surface mass balance during the last 800 yr. which claimed:

    The temporal and spatial variability of the
    SMB over the previous 800 yr indicates that SMB changes
    over most of Antarctica are statistically negligible and do not
    exhibit an overall clear trend. This result is in accordance
    with the results presented by Monaghan et al. (2006), which
    demonstrate statistically insignificant changes in the SMB
    over the past 50 yr.

    Catch that? NEGLIGIBLE, meaning not melting at all in a meaningful sense.

  32. dave says:
    July 16, 2013 at 10:11 am

    “Half of that rise might come from ice-loss in Antarctica which is currently contributing less than 10 percent to global sea-level rise.”

    I thought the ice extent for Antarctica is near its record for the satellite era. Where did the nearly 10 percent come from? The extent is near record but the volume is substantially reduced?

    Well, ice floats. That means that ice from the ice shelves displaces water equivalent to the mass of the ice, ergo, more ice, less room for liquid. They just meant “ice-gain.” It was a typo due the AGW mindset. /sarc

  33. This is really just a silly number-crunching exercise.

    For example. Sea level is currently increasing at 1.4 mms/year. Times 2,000 years equals 2.8 metres. If you want to say the rate will increase in the future, then that is just a silly assumption-based model.

    So, we were already on-track to have sea level rise as the current interglacial continues to go on and continues to melt some of the marginal glacial ice which built up during the last ice age. The southern part of Greenland, for example, is too far south to have substantial glaciers. If the interglacial continues for another 8,000 years, there is going to be little glacier left in southern Greenland.

    Regarding the comments in the news release that CO2 has a long lifetime in the atmosphere. This is just AGW doom and gloom again (which they strangely seem to find self-satisfying somehow). The Oceans, plants and soils will absorb out all the extra CO2 we have added to the atmosphere in around 125 years once we stop adding it. If we just cut our emissions by half, the CO2 level will stabilize. Scientists who say it will stay around for thousands of years are simply lying (assuming they would have the knowledge about the basic Carbon cycle numbers and drivers which any scientist who comments on the issue should do first).

  34. Thanks, Jimbo (at 10:31 AM 7/16/13) — THAT
    [http://tomnelson.blogspot.com/2013/07/don-miss-this-from-climate-skeptics-is.html]
    was encouraging! COOL!

    (from article cited by Jimbo)
    “In April last year, Paul Ingrassia (then [Reuters] deputy editor-in-chief) and I met and had a chat … He told me he was a climate change sceptic. … someone who wanted to see more evidence mankind was changing the global climate.

    Progressively, getting any climate change-themed story published got harder [Ha, HA!]. …

    Very soon after that conversation I was told my climate change role was abolished. I was asked to take over the regional shipping role [LOL] and that I had less than a week to decide…I decided it was time to leave. ["Don't let the hockey stick hit you on the way out! Bwah, ha, ha, ha, ha, haaaaaaaaaaaaaa!" Ingrassia WANTED to say, heh, heh.]

    BTW, Jimbo, I suppose you are now sound asleep, but, I sure hope your (and Mr. Lambert‘s) electricity is back on!

    Take care, O Excellent Researcher.

    J.

  35. Tim Folkerts says:
    July 16, 2013 at 10:44 am
    @ dave, July 16, 2013 at 10:11 am

    You are confusing sea ice (typically a few meters thick floating in the oceans) with ice sheets (typically a few km thick resting on land). Floating sea ice will have minimal impacts on sea level. Land-based ice sheets can have a large impact if the H2O flows off into the ocean.

    My understanding is this (please correct me if I’m wrong: There are three types of ice in Antarctica:

    Free-floating sea-ice
    “Ice shelves” that are connected to land but float in the sea
    Land ice

    The shelves can melt or grow independently of what’s happening with the other two components.

  36. Ian W July 16, 2013 at 10:59 am

    the water level in the city of Amsterdam is nowadays structural minus 20 cm in summer and minus 40 cm in winter, compared to the NAP, which is related to historical mean sea level;

    Amsterdam is founded in the 1200’s: if we call that period the medieval warm period, we see first a cooling down to the little ice age, accumulating of ice in Greenland and a decreasing sea level;

    with the start of anthropogenic global warming, the sea starts to rise with the result that Amsterdam is now below the former mean sea levels, recorded from the 1700’s;

    we survive because there are expensive and impressive protective dikes and other megastructures that have costed billions to keep to sea out of our city and the surrounding countryside;

    only ad the very moment of the low tide we can undo ourselves passively from the water that comes from the sky or with the river Rhine from Germany and Switserland;

    concluding: personnaly I dont see any conflict with the comprehensive computer simulations from Levermanns study as you suggest;

  37. The Antarctic computer simulations were able to simulate the past five million years of ice history

    Ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha!

    Even with multiple satellites and all the other sophisticated measuring tools of the 21st century they haven’t got a clue whether Antarctica is gaining or losing ice at the moment.

    [Their] simulations are utterly worthless.

    Climate change is a post-graduate employment scheme.

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