Text 11819, 83 rader
Skriven 2007-02-08 19:56:37 av Christophe Bachmann (15259.babylon5)
  Kommentar till text 11818 av rec.arts.sf.tv.babylon5.moderated (15258.babylon5)
Ärende: Re: Global warming, among other things
==============================================


Shabaz a =E9crit :
> On Feb 8, 5:50 pm, Christophe Bachmann <Chris_...@Compuserve.com>
> wrote:

[As an aside was my screen name mangled by technical considerations or=20
is there something that could cause disagreements ?]

>> Please, let's not be over-alarmist. I agree absolutely that something
>> big must be done very soon if we want to avoid very bad things, but th=
e
>> IPCC :
>>
>> http://www.ipcc.ch/
>>
>> has stated that the increase in sea levels would most likely (>90%
>> confidence) be less than 58 cm (less than two feet) in the next 100 ye=
ars.
>> The problem with "global warming" is that it is a very complex thing
>> that can have a lot of quite unintended consequences. If you want the
>> word straight from the horse's mouth please download :
>>
>> http://www.ipcc.ch/SPM2feb07.pdf
>>
>> the Summary for Policymakers of the first volume of "Climate Change
>> 2007" of the Working Group I of the Intergovernmental Panel on Climate
>> Change (IPCC), also known as the Fourth Assessment Report (AR4).
>>
>=20
> 20 foot sounds wrong to me too. I think that number is from the
> potential sea level rise if one of the big ice reserves, like
> greenland or the arctic, would melt entirely. And while there are
> studies that show increasing vulnerability to warming in these areas,
> it's not really part of any projections at this point, and certainly
> not projected to happen completely with any certainty within a hundred
> years, far as I know.
>=20
> But the IPCC AR4 SPM didn't quite say "most likely (>90% confidence)
> be less than 58 cm" either. The IPCC runs several scenarios to predict
> temperature rise and sea level rise, and 59 cm is the top level range
> of the "high scenario" A1FI, which basically has the world developing
> towards globalisation and with a technological focus that is fossil
> intensive (entire range for that scenario is 26 - 59 cm). However, the
> model predictions for this assessment report did not include one very
> important factor this time: ice sheet flow dynamics. Basically, our
> understanding has gone up about them a bit which actually has led to
> two realizations: the impact of ice sheet flow dynamics could be
> higher than we thought, and we now can actually say things with less
> certainty than we previously could. So, in contrast with the TAR, the
> models do not "include the full effects of changes in ice sheet flow,
> because a basis in published literature is lacking". Which has
> actually lead to lower sea level estimates compared to the TAR sea
> level rise estimates (88 cm for the top end range for the highest
> scenario), which lead to some confusion, since not everyone realized
> that one included these dynamics and one didn't, making it impossible
> to compare the estimates directly, since it is apples and oranges.
>=20
> The AR4 SPM does mention that recent observation suggest that these
> dynamics could lead to extra sea level rise, even though they can't
> say how much at this point: "Dynamical processes related to ice flow
> not included in current models but suggested by recent observations
> could increase the vulnerability of the ice sheets to warming,
> increasing future sea level rise. Understanding of these processes is
> limited and there is no consensus on their magnitude." .
>=20
> RealClimate also mentions this at the end of their initial analysis of
> the AR4 SPM here: http://tinyurl.com/2w6vqf which explains it probably
> a bit more clearly than me. ;)
>=20
> -Shabaz
>=20
>=20
Thanks for the clarification, indeed I oversimplified a little, but 59=20
or 88 cm (23 or 35 inches) are very far from the stated twenty feet and=20
the exact height falls within the many unforeseen and perhaps=20
unforeseeable (rather than unintended as I stated) consequences of AGW.
--=20
Greetings, Salutations,
Guiraud Belissen, Ch=E2teau du Ciel, Drachenwald,
Chris CII, Rennes, France
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