Text 11869, 65 rader
Skriven 2007-02-09 00:55:45 av Shabaz (15310.babylon5)
  Kommentar till text 11868 av rec.arts.sf.tv.babylon5.moderated (15309.babylon5)
Ärende: Re: Global warming, among other things
==============================================
On Feb 9, 8:09 am, "Soundy" <soundy...@gmail.com> wrote:
> On Feb 8, 10:42 am, "Shabaz" <shaba...@gmail.com> wrote:
>
> > 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...
>
> Two issues with this:
>
> 1. These "scearios, or "models," are generated only on existing known
> data, which when it comes to long-term climate will ALWAYS be
> incomplete to some degree (pardon the pun).  How much of an effect the
> missing data will have is even an unknown - a tiny difference in one
> area may cause significant changes in the model.  Someone may discover
> something TOMORROW in a glacial core sample that will turn all the
> models completely upside-down.

The scenarios are not the same thing as the models. The SRES scenarios
project what is deemed a plausible development of the future, and
don't really concern climatic effects at all. Each of these scenarios
is then run across various climate models, to get likely ranges. The
accuracy and number of models has gone up steadily over the years,
allowing for a pretty good basis for projections in the IPCC AR4.
While I know the general gist of the backgrounds of the various SRES
scenarios, I've never really read up on them in depth, but if you feel
like doing so you can find in depth information on them here: http://
www.ipcc.ch/pub/sres-e.pdf

As for your point that it is only based on known data... um, yes, of
course? This is true for all science, and what you're saying seems
almost like a restatement of the induction problem, more than anything
else. However, what you seem to be implying is that there is something
that inherently prevents models from ever having predictive power in a
useful manner, which is simply not true. If you want to know how
accurate predictions using multiple models are, there is paper on this
which is discussed at RealClimate here: http://tinyurl.com/yzdled

And if you want more info on climate models and how they work,
RealClimate again has a nice and readable write up: http://tinyurl.com/
yxvqac

> 2. None of the models can account for the unforseen.  A Krakatoa-sized
> volcanic eruption would completely blow any warming models out of the
> (rising) water... and could happen next week.  Point of the matter is,
> this planet has an amazing knack for taking care of herself, sometimes
> in very dramatic fashion.

Average volcanic activity is accounted for in models and has been for
decades, far as I know. There is of course always the chance that
something will happen that is so unlikely that it isn't accounted for
in models (a super volcano pops, an asteroids hits, whatever), but
that's because these things are believed to be _unlikely to happen_.
But things like volcano eruptions are understood with a high enough
degree that they are accounted for in models, and certainly wouldn't
"blow any warming models out of the (rising) water".

As for the planet taking care of itself; the problem is not one for
the planet, but for us. We're introducing forcings that can induce
changes more rapid and significant than pretty much any in the period
our civilization has developed itself in. Rapid changes which could
cause significant problems for us being able to adapt ourself, even if
"the planet" would shrug it off in the time scales it operates on.

-Shabaz
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