[Coral-List] Atolls and SL rise

Tue Oct 5 05:09:25 EDT 2010

  Dear Listers and Bill

Bill makes a very valid point for the seasonal influences in the 
Maldives where (particularly in the northern islands) there is a 
significant difference as Han et al point out. However, further south in 
the Chagos for example, this is not the case. The Han et al model shows 
a lot of heterogeneity both overall and seasonally throughout the Indian 
Ocean which emphasises the regional nature of long term sea-level changes.

Richard P Dunne

On 05/10/2010 03:13, Bill Allison wrote:
>
> 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 
> <mailto: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/
>     <http://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
>     > _______________________________________________
>     > Coral-List mailing list
>     > Coral-List at coral.aoml.noaa.gov
>     <mailto:Coral-List at coral.aoml.noaa.gov>
>     > http://coral.aoml.noaa.gov/mailman/listinfo/coral-list
>     _______________________________________________
>     Coral-List mailing list
>     Coral-List at coral.aoml.noaa.gov <mailto:Coral-List at coral.aoml.noaa.gov>
>     http://coral.aoml.noaa.gov/mailman/listinfo/coral-list
>
>
>
>
> -- 
> ________________________________
> "reality leaves a lot to the imagination..."  John Lennon