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Will the Earth really flood when global warming happens?

  1. Dec 3, 2009 #1
    Will the Earth really flood when global warming happens? Seems far from definitive and far less clear than the science behind global warming. I remember my Oceanography professor challenging the notion that global warming would raise sea-level, shut off gulf stream, thermohaline circulation. My professor seemed most skeptical of sea-level rise, perhaps because it is more political than the other possible changes or possibly because it's easier to make a Hollywood picture about sea-level rise than it is about the Atlantic thermohaline current shut down.
     
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  3. Dec 3, 2009 #2

    vanesch

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    I think the worst case predictions for the coming century have an upper bound of about 2 meters (this was written in the Copenhagen update of the IPCC report, discussed in another thread here https://www.physicsforums.com/showthread.php?t=358328 )

    That is problematic for some islands - I don't know how problematic that is for most coastal regions, if you throw in some civil engineering like the Dutch are used to.

    (Amsterdam lies below sea level).
     
  4. Dec 3, 2009 #3
    I honestly think the whole global warming phenomena is overblown. Unless water levels rise dramatically (and I mean hundreds of feet), then I really don't see a major impact on our ecosystems- with the exception on how this will effect coastal animal habitats.
     
  5. Dec 3, 2009 #4

    DaveC426913

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    Considering how much diversity there is in those coastal habitats, as well as how much of the human population lives in those coastal areas, I don't think it's overblown.
     
  6. Dec 3, 2009 #5

    D H

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    You've been listening to too many granola heads. There are wackos on both sides of the global warming debate, and the wackos on the left care more for polar bears and the fragile environment than they do for humanity. The fragile environment is pretty dang robust. (Aside: The sheer number of humans around does a lot more harm to the environment than a few meter rise in sea level will do.)

    Our modern society is not so robust. A few meters rise probably will result in significant economic damage.
     
  7. Dec 3, 2009 #6

    mgb_phys

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    A 1m rise would make London and Manhattan look a lot like New Orleans (afterwards)
     
  8. Dec 3, 2009 #7
    I encourage all believers in a two meter rise in sea level to invest in future beachfront property at discount prices.
     
  9. Dec 4, 2009 #8
    2 meters would be a bummer in Florida.
     
  10. Dec 4, 2009 #9
    Hi there,

    It always depends which theory you look at. Some theories (the ones that are really scary) say that the water level will rise way above the MontBlanc in France.

    I happened to look at some method that brings everything back into proportions, which states that the Alestch Glacier (the biggest glacier in the Alps) has enough water to barely fill the Geneva lake (89km^3). Therefore, which theory to believe is up to everyone, but we might be blowing global warming and its effect out of proportion.

    Cheers
     
  11. Dec 4, 2009 #10
    Could anybody reproduce that peer reviewed article that claimes two meters?

    Is this just written for the trashcan?

    Siddall et all 2009; Constraints on future sea-level rise from past sea-level change; Nature Geoscience 2, 571 - 575 (2009) Published online: 26 July 2009 | doi:10.1038/ngeo587 ,

    This is the graph of current sea level rise, issued by the University of Colorado:

    dc5the.jpg

    How does that compare to:

    (see here)

    Note that we have a fourth assessment report since 2007, so why wasn't that used for reference?

    Does anybody happen notice that "accerelation" in the last few years?
     
    Last edited: Dec 4, 2009
  12. Dec 4, 2009 #11

    vanesch

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    No, that its rise will have an UPPER LIMIT of at MOST 2 meters.

    http://www.sciencemag.org/cgi/content/abstract/1135456

    This is one of the references given in the Copenhagen Climate Update Report, of which we talked about in the other thread here that justifies their claim that the rise will not be larger than 2 meters in 2100.
     
  13. Dec 4, 2009 #12
    The article of Rahmsdorf is 2006, the "upper limit" of Siddall et al 2009 is 82 cm.

    As far as I recall there was also a upper limit of a climate sensitivity of 11 or so degrees per doubling CO2 in one model run.
    Maybe we can also claim that the sea level rise will not exceed 70 meters in 2100.
     
  14. Dec 4, 2009 #13
    Anyway, it may be known that the start of the Holocene was exceptional warm, the period is known as the Holocene Thermal Optimum that lasting from about 9000 - 6000 years ago with temperatures several degrees degrees warmer than today. The warmth can be explained by an insolation maximum due to a maximum obliquity. We wondered sometimes why this period is not called the "Holocene Thermal Catastrophy", on the contrary, it's the time of the early civilisations to emerge.

    Anyway, non of the ice sheets melted in that period of several thousand years and there are no indications that sea level rise (after the glacial period) accellerated abnormally as a reaction to the warmth.

    1zcoemt.png

    References figure compiled by Robert A. Rohde

    Fleming, Kevin, Paul Johnston, Dan Zwartz, Yusuke Yokoyama, Kurt Lambeck and John Chappell (1998). "Refining the eustatic sea-level curve since the Last Glacial Maximum using far- and intermediate-field sites". Earth and Planetary Science Letters 163 (1-4): 327-342. doi:10.1016/S0012-821X(98)00198-8
    Fleming, Kevin Michael (2000). Glacial Rebound and Sea-level Change Constraints on the Greenland Ice Sheet. Australian National University. PhD Thesis.
    Milne, Glenn A., Antony J. Long and Sophie E. Bassett (2005). "Modelling Holocene relative sea-level observations from the Caribbean and South America". Quaternary Science Reviews 24 (10-11): 1183-1202. doi:10.1016/j.quascirev.2004.10.005
    Morhange, C., J. Laborel, A. Hesnard (2001). "Changes of relative sea level during the past 5000 years in the ancient harbor of Marseilles, Southern France". Palaeogeography, Palaeoclimatology, Palaeoecology 166: 319-329.
     
    Last edited: Dec 4, 2009
  15. Dec 4, 2009 #14
    Given characteristic vertical scale of Earth's terrain on the order of 10 km, a 2 m rise would decrease the amount of available land by something like 0.02% (assuming no effort to protect valuable coastal real estate from flooding).

    Even coastal cities usually have the bulk of their areas at significant elevations above sea level. For example, Manhattan is one of the flattest, lowest-lying cities in the United States. 2 m rise could be enough to submerge parts of WTC site (which is almost next to the water to begin with), but the foot of the Empire State Building is 14 m above sea level, and much of the Central Park is at 20-40 m, so neither of those would be affected by any foreseeable level of sea level rise. In San Francisco, the damage would be limited to a couple of blocks closest to the coast here and there.

    So, the projected rate of sea level rise is not likely to cause significant economic damage to major countries. Some people's waterfront homes will become underwater homes, some tiny Oceanic atolls will become completely submerged, but all that is hardly significant.

    There's simply not enough water on Earth to cause economically significant amounts of flooding. Even if all of Antarctica's ice were to melt, that would rise the sea level by ~40 m. And we all know that it's not going to happen, short of some cataclysmic event involving a pole shift, because much of Antarctica's surface is deep-frozen, with three to five months a year of polar nights and daily summer highs below -20 °C.
     
    Last edited: Dec 4, 2009
  16. Dec 4, 2009 #15

    D H

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    You are forgetting harbors and ports. The vast majority just happen to be *at* sea level.
     
  17. Dec 4, 2009 #16

    They are not *at*, sea level, they are slightly above sea level. If they were at sea level, they'd get flooded by unusually high tides and onshore winds (not to mention tsunamis).

    So, to protect against flooding, they are raised above sea level on pillars, like this:

    http://upload.wikimedia.org/wikipedia/en/thumb/1/1e/NewportPier1.jpg/800px-NewportPier1.jpg [Broken]

    Besides, at the timescales we're talking about (50 to 100 years), most manmade harbor & port constructions (buildings, piers, etc) will need to be rebuilt at some point anyway.
     
    Last edited by a moderator: May 4, 2017
  18. Dec 4, 2009 #17

    vanesch

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    So if Rahmsdorf has something like 1.4 m as an upper limit from his analysis, and Siddall 0.82 m as an upper limit from their analysis, and probably others another value, then it is reasonable to say that an upper limit of worse case is 2 m, no ?

    1 m would not include Rahmsdorf and so wouldn't be "worst case", no ?

    Worst case as in worst case of the paper that has the highest estimates.
     
  19. Dec 4, 2009 #18

    mgb_phys

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    The world's oceans are on average about 3000m deep, if they warmed up enough to expand by 0.03% that's a 1m rise in sea level.
     
  20. Dec 4, 2009 #19

    mgb_phys

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    IIRC the oceans turn out to be a lucky break, because of water's odd density behavior a degree temperature change doesn't have much of an effect on the sea level.

    London is in trouble from storm surges if increased temperatures lead to more violent weather, and it doesn't help that it's sinking at about the same rate as the current sea level rise. But that's their fault for building the place in a swamp.
     
  21. Dec 23, 2009 #20

    Xnn

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    Here's the deal; sea levels are currently rising about 3 mm/year on average. Over a century that works out to about 30cm or 1 foot of rise; not a big deal. As global temperatures rise, the rate of sea level rise is likely to accelerate. However, based on paleodata, it's unlikely to exceed 2cm/yr.

    The last time atmospheric CO2 levels were similar to today was about 3 million years ago during the Middle Pliocene. During that time, sea levels were between 20 to 30 meters higher than they are right now. However at 2cm/year, it would still take over a thousand years to realize that amount of change.

    So, bottom line, the rate of rise is slow enough that human civilization can rebuild infrastructure quick enough to adopt to the change. However, over the long term there will be a significant change to the coastlines.

    Here's a paper from Nature on the subject:

    http://www.nature.com/ngeo/journal/v2/n7/abs/ngeo557.html

     
    Last edited: Dec 23, 2009
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