[Coral-List] new "business as usual" projections for climate change

[Arthur]

Hi Doug,

Thanks for sharing this link. This is important, not just to the 
mitigation discussions and targets, but also the adaptation discussion. 
I work at the pointy end of adaptation in the low lying atolls of the 
Central Pacific. Some consensus on what type of future we are 
preparing/designing for would indeed be helpful but I fear 9 times out 
of 10 the accountants are making that decision anyway, not the science.

Whatever the case, my sincere advice out here is that we do adopt RCP8.5 
/ 2100 as our nominal adaptation horizon. Not because it can be 
perfectly argued but because it's a simple precautionary principle and 
driven by the local realities of adaptation needs, not the global 
politics and economics of emissions mitigation. For us sea level rise is 
our biggest immediate headache (of course closely followed by reef 
ecosystem demise - this is coral list after all) but if you look at the 
literature since IPCC AR5, (e.g. Le Cozannet et al 2019 /Low-End 
Probabilistic Sea-Level Projections/) RCP 8.5 SLR scenarios seem to be a 
real possibility. I'd be delighted to be shown to be in error on this 
but until then, we know what we know, and better to design for the worst 
end now whilst we still have the chance.

SLR is climbing inexorably upwards, our region experiences higher rates 
than many parts of the world and many of our islands are extraordinarily 
low. 46% of the land area of the central part of Fogafale the capital of 
Tuvalu and home to the greater part of the national population, is 
already, during the highest measured sea levels since 1993 (I say again 
measured levels, not projected) below that figure. Now no one can argue 
this island was not always a finely balanced situation for its 
inhabitants and any perturbation in sea level has an effect. But sea 
level rise is now set in motion because of our emissions and its 
extremely unlikely to flatten out by 2100. All RCP values other than 
perhaps 2.6 (good luck with that ........) are problematic in these 
types of locations. For us, if it turns out we've over engineered by 
using a mid range RCP8.5 / 2100 horizon, it almost certainly means we've 
simply bought more time, protected from a bigger storm, we're better 
prepared for the next big drought - whatever it is its not wasted resources.

Finally, the first thing I did when I read that paper was search for the 
words "methane" and "feedback". The authors do deal with this and I 
can't fault their thinking - I'm not likely qualified to. But neither am 
I convinced by their treatment of those issues. There is little doubt 
ones perception of those poorly understood feedback mechanisms and risks 
and ones subsequent willingness to leave them on the back shelf, will be 
coloured by whether you live, work and raise your family in a large 
better resourced developed economy or a small isolated atoll.

Arthur

Arthur Webb
Senior Fellow - ANCORS
University of Wollongong

webbarthur at gmail.com




On 05/02/2020 10:42, Douglas Fenner via Coral-List wrote:
> As we all know, global warming and acidification are huge threats to the
> future of corals.  Here are a discussion of some new insights into what is
> probable, if we don't take action.  Not quite as bad as had been projected,
> but still a "disaster" if we don't act.
>
> Cheers, Doug
>
> https://www.nature.com/articles/d41586-020-00177-3?utm_source=Nature+Briefing&utm_campaign=ee09f96136-briefing-dy-20200130&utm_medium=email&utm_term=0_c9dfd39373-ee09f96136-43423877
>
>
>