Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Say goodbye to Miami and new Orleans

  1. Oct 13, 2015 #1


    User Avatar
    Gold Member


    Say goodbye to Miami and New Orleans. No matter what we do to curb global warming, these and other beloved U.S. cities will sink below rising seas, according to a study Monday.

    But making extreme carbon cuts and moving to renewable energy could save millions of people living in iconic coastal areas of the United States, said the findings in the Oct. 12 edition of the Proceedings of the National Academy of Sciences, a peer-reviewed journal.

    video-icon.png PLAY VIDEO
    Global Warming And Climate Change: What's The Diff?

    We hear the two terms used all the time, often interchangeably. What's the meaning of these words and how do people perceive them?
    Scientists have already established that if we do nothing to reduce our burning of fossil fuel up to the year 2100, the planet will face sea level rise of 14-32 feet (4.3–9.9 meters), said lead author Ben Strauss, vice president for sea level and climate impacts at Climate Central.

    That is in the near future, can building up levies save these cities?
  2. jcsd
  3. Oct 13, 2015 #2


    User Avatar
    Education Advisor
    Gold Member

    Um... 4 meters by 2100? Nah. The reasonable estimates are about 0.3 meters. This rate has been sustained with little change for the last more than 150 years. Note, it has *NOT* accelerated during the increase in CO2 of the industrial age. To get that 4 meters you would need much more than 85 years. You would need more like 1000 years.

    1000 years ago, who lived in Florida? 1000 years from now, who will live in Florida? Can you give even the haziest guess at a prediction of what humanity will be worrying about in 1000 years? Maybe the Nox will have arrived by then and wave their arms and change everything.


    As to NO, parts of it are already several meters below sea level. What a ridiculous city.
  4. Oct 13, 2015 #3

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    While that is certainly the implication of the discovery.com article to which @wolram linked (and many other similar pop sci articles), that is not what the PNAS article says. The article instead addresses the concept of "committed" or "locked-in" sea level rise. This is how much sea level will eventually rise, within the next 2000 years or so, given various CO2 scenarios. In particular, what the article says is that the collapse of the West Antarctic Ice Sheet will be inevitable should carbon emissions continue unabated for the next 84 years (i.e., until 2100). The article does not say this collapse will happen by 2100.

    For now (but probably not for long), the full text of the article is freely available at pnas.org at http://www.pnas.org/content/early/2015/10/07/1511186112.full.pdf .
  5. Oct 14, 2015 #4
    I am not sure it is a fair assumption that our CO2 emissions will continue to grow through 2100.
    The use of Fracking and other enhanced recovery techniques, is evidence that the era of cheap
    easy oil, is coming to an end.
    The most likely near term scenario, is that oil companies will use wholesale electricity, to make their
    own feedstock, that would be carbon neutral.
    Such a solution would solve several problems.
    Dense energy storage being the biggest one.
    If CO2 is a problem, that would be solved by solving the energy storage problem.
  6. Oct 14, 2015 #5

    jim mcnamara

    User Avatar

    Staff: Mentor

    Could you please provide a reasonable citation - You do understand that every energy transformation step is not 100% efficient. Entropy eats energy up. So something has to be used to create the lost energy at the electric plant - fossil fuel, hydro, or nuclear. In the US nuclear is going nowhere, and hydro is limited. What you are proposing, a priori, appears to be a perpetual motion "gizmo". They do not exist.

    I could be wrong or misunderstand what you really mean, so correct me.

    But, fair warning, perpetual motion/energy is a fast path to being asked to leave the forums.
  7. Oct 15, 2015 #6
    Sorry, several years ago, Fraunhofer University started looking into how to store Germany's surplus solar power
    for winter heating.
    The un-natural gas would be carbon neutral, as the carbon was coming from atmospheric CO2.
    Audi, picked up on the research, bought an old refinery, and started looking into the process,
    and later began working on liquid fuels.
    Meanwhile the Naval Research Labs, thought the idea of a carrier making their own jet fuel, would be useful.
    Bear in mind this is energy storage, the energy must still come from somewhere.
    Audi, is claiming the process is now up to 70% efficient, which means it would take
    50 Kwh to make a gallon of gasoline, and about 55 Kwh to make a gallon of diesel or jet fuel.
    The big shortfall of the majority of alternative energies is density and storage.
    Short of some amazing technology breakthrough batteries are not up to the job, of storing
    enough energy in a package light enough, to power a jet several thousand miles.
  8. Oct 15, 2015 #7


    User Avatar
    Gold Member

    The IPCC AR5 sea level rise projections are shown below. The pathway or RCP that we appear to currently approximate is something like RCP 4.5 or 6.0, with mean SLR of 0.47m (19") by 2100. RCP 8.5 seems unlikely as it assumes outcomes such as coal use growing by eight fold and population reaching 12 to 13 billion, well above the current UN estimate of 11.2B.
  9. Oct 15, 2015 #8
    Because we know so little about events as long ago as end-Permian we do not have a solid grasp on a number of variables that can act as tipping points and quite naturally and correctly graphs showing predicted rates of change omit these variables. There are at least four (4) such possible trigger point mechanisms known to be at least possible and just one of them is sufficient to produce radical change to currently possible estimates.

    For example -
    Given such serious risk I think it behooves us to remain clear and conservative in public forums and especially in US media which is where it seems more unreasonable skepticism and even outright denial (replete with conspiracy theory and denegration of Science as a whole) exists, but also to be very clear about what issues require active (and possibly expensive) focused research. Example - while the number looks small on paper even an average of 0.3 meters is not a trivial change with ignorable consequences. Somehow this truly needs to become common knowledge long before it becomes absolutely undeniable as a fait accompli.
  10. Oct 19, 2015 #9
    An important detail that gets constantly overlooked is that the ocean rise is not just a result of melting ice. Thermal expansion of water is also an important factor.

    1. The average depth of the ocean is about 12,100 feet.

    2. The average temperature of the ocean is about 3.5-degrees C. The ocean average reflects warm equatorial, surface water and cold, deep water.
    http://savethesea.org/STS ocean_facts.htm

    3. Water's density varies with temperature. Above about 4-degrees C, the density decreases as water expands (thermally). This leads to stable temperature gradients.

    Say that the ocean average temperature rises by 1-degrees C. If it was pure water, the density would go from 1.0000000 to 0.9999668. That is a density change of 0.0000332. For a 12,100 foot depth, that is an increase of 0.4 feet.

    The ocean temperature is increasing in average surface temperature, and the density change from 16-degrees C to 17-degrees C for pure water is from 0.9989460 to 0.9987779, a change of 0.0001681 ... 5 times larger change in density.

    Now if ice melts, it will cool the surface temperature, so the volume increase from water addition is countered by the volume decrease from temperature decrease. If circulation changes, then mixing will decrease surface temperatures, and increase deeper temperatures, which has a net decrease, due to the fact that the expansion is greater at higher temperatures.

    It is clearly more complicated than just calculating how much water is poured into the ocean from melting ice off land masses.
  11. Oct 19, 2015 #10


    User Avatar
    Gold Member

    The IPCC breaks down sea level rise by the various components: thermal expansion, glaciers, Greenland ice sheet, Antarctic ice sheet, ice sheet dynamics, land water storage. Thermal expansion is the largest contribution, 30%-55% of the total SLR.


    Brief from lead author of IPCC AR5 Sea Level Rise here.

    The IPCC's assessment of thermal expansion slowed a third between its AR4 report to AR5. AR5, 1993-2010: 1.1 mm/yr (Table 13.1, pg 1151 Chapter 13), AR4, 1993-2003: 1.6 mm/yr. Greenland's ice sheet contribution increased between AR4 and AR5.
  12. Oct 19, 2015 #11
    There are a LOT of other factors too, about what a rise in sea level would do...This for a few reasons. One,it can add to the height of a full tide, making the force add to the power of a storm swell, say on a levee, dam, etc.- significantly larger (by a huge factor); two, its motion (over the top) can wash away the material holding an Earthen (or other) dam to fail; three, because water is such an incompressible liquid, it can be used as a hydraulic fluid, like oil. So, it can transport a large amount of pressure, via a small rise in fluid level.

    As a result crossing a stream that is only a foot thick is not as much of a problem as crossing one that is two or more feet deep.. Deeper water flows can sweep away trucks, buses, buildings, etc. no problem.
  13. Oct 19, 2015 #12


    User Avatar

    Staff: Mentor

    It seems we've gotten away from hard science and into anecdotes.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook