[Coral-List] Atolls and SL rise

[Bill Allison]

As I pointed out in my post of Sep 30, 2010, Han et al. (2010) also
suggested on page 549 that seasonal variation in sea level could have
significant effects.



"However, statistically significant sea-level rise is shown during winter in
both ocean general circulation models and Simple Ocean Data Assimilation
data (Supplementary Fig. S2), which could have significant impacts on the
Maldives because of its low elevation." p. 549



Factor in storm surge or a tsunami riding on the back of such variation and
the risk increases appreciably.





On Mon, Oct 4, 2010 at 7:41 AM, Richard Dunne <RichardPDunne at aol.com> wrote:

>  Dear Paul and List
>
> By casting aside the more recent evidence from Han et al 2010 (Nature
> Geoscience) into the category of "a little absurd" you fail to
> distinguish between regional sea-level rise and globally averaged
> effects, between analysis which incorporate regional ocean-atmosphere
> circulation changes and which do not, between examination of recent
> (from the 1960s up to 2008) rates of change, and those incorporating
> semi-empirical modelled and predicted events. These things cannot be
> easily resolved or selectively dismissed in this way.
>
> Han et al. conclude "Our results indicate that warming-induced regional
> atmospheric circulation changes - although challenging for climate
> models, especially over the Indian monsoon region - should be considered
> seriously, together with thermal expansion, melting land ice and natural
> variability, to achieve reliable regional sea-level and climate
> prediction."
>
> A recent comprehensive review of of sea-level rise by Cazenave & Llovel
> (Annual Reviews of Marine Science 2010) considers an earlier paper by
> Rahmstorf (2007) which like the recent Vermeer & Rahmstorf (2009)
> produced comparable values of between 50 and 120cm by 2100, describing
> it as "offering plausible ranges of future sea-level rise and an
> interesting alternative to still uncertain coupled climate model
> projections.".
>
> Also, if it is indeed "widely accepted" as you say, that the IPCC AR4
> (AB1) scenario for future globally averaged sea-level rise is a serious
> underestimation then why for example do the eminent scientists of the
> Royal Society (Climate change: a summary of the science. Sept 2010) not
> share these views? There is no evidence that they accept the large
> values that you cite, quite the contrary. They conclude that "Because of
> the thermal expansion of the ocean, it is very likely that for many
> centuries the rate of global sea-level rise will be at least as large as
> the rate of 20 cm per century that has been observed over the past
> century." and "There is currently insufficient understanding of the
> enhanced melting and retreat of the ice sheets on Greenland and West
> Antarctica to predict exactly how much the rate of sea level rise will
> increase above that observed in the past century for a given temperature
> increase."
>
> This is, and remains an area of considerable uncertainty and controversy
> and I dare say will remain so until a reliable longer term dataset has
> accumulated. In the meantime we should be cautious to oversimplify the
> issues involved and close our minds to all the alternatives.
>
> Richard P Dunne
>
>
>
>
> On 03/10/2010 05:08, Paul Blanchon wrote:
> > Dear Richard and list,
> >
> > The argument that some atolls  "may survive for generations"  and
> > should be considered for re-population seems just a little absurd,
> > regardless of the politics.
> > It is widely accepted that not only is the IPCC AR4 prediction of SL
> > rise a serious underestimation, but that over the last few decades
> > "...sea level has in fact risen 50% more than predicted by its
> > models..."  (see the illuminating climate-science blog at:
> > www.realclimate.org/index.php/archives/2010/03/ippc-sealevel-gate/).
> >
> > The IPCC underestimation has been the subject of several subsequent
> > publications which all conclude SL rise by 2100 will likely exceed one
> > meter: for example, Vermeer and Rahmstorf 2009 (PNAS 106: 21527-21532)
> > predict average rates over the 21st century will be 8-18 mm/year.
> > Thus, as Chip Fletcher implies, the experience of Micronesians is
> > likely to be repeated in all low-lying coastal communities, regardless
> > of past or future regional variation.
> >
> > Re-population of any atoll would therefore seem to be an exceptionally
> bad idea.
> >
> > Saludos,
> > Paul.
> >
> > Paul Blanchon
> > Marine Geoscience Lab.,
> > Reef Systems Unit,
> > Institute of Marine Sciences&  Limnology
> > National Autonomous University of Mexico
> > Tel. +52  (998) 87-10009 Ext 166
> > _______________________________________________
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> > Coral-List at coral.aoml.noaa.gov
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________________________________
"reality leaves a lot to the imagination..."  John Lennon