It is the case that very fast climate change of any sort makes prediction
more difficult. We are not talking about a "little" warming at least in
terms of the rate of change as compared with natural events. Even the
absolute change is strikingly large in the AR4 assessment's 2100 map.
The ice catastrophes (there are two candidates with very different details)
are the current leading candidate. The worry about a collapse of the
thermohaline circulation appears to have abated under further investigation.
Perhaps other phenomena lurk. Clathrates, anyone?
Until very recently glacier dynamics was a pure science. Its transition to
an applied science will be interesting.
Let's hope the 50 year scenario can be excluded soon. I have heard
informally from one informed source that we might not have that good
fortune. It is not surprising that we have entered a time when few are
willing to publicly hazard an estimate on this matter. A good deal of
research money is indded shifting toward this question.
There's also a philosophical question of whether it is reasonable to commit
to a 500 year time scale of huge coastal flooding if it might still be
avoided.
mt
On 2/15/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
>
>
> > It's genuinely difficult to get meaningful personal probabilities of
> > highly unlikely (but poorly understood) events. Considering it as odds
> > on a fair bet gets tangled up with risk-aversion (ie they might prefer
> > the unlikelier side even with an expected loss, thus understating the
> > odds that they really think are fair).
> >
> > It's doubly difficult now that many people have learnt how politically
> > powerful the "can't rule it out" appeal to risk-aversion can be.
>
> I accept that it may be difficult to get good values for
> probabilities, but, if the possibility of 5m in 50 years is a
> realistic event to fear, having a better understanding of ice sheet
> dynamics is surely worth quite a lot? And rather than demand that
> trillions be spent based on poorly understood science (possibly
> science that has no more than a few hundred scientists working on it
> with a budget of a few hundred million), I ask, whether that
> uncertainty could be substantially reduced with a by comparison modest
> expenditure (say a few billion, or even tens of billions)?
>
> Incidentally, insurance against low likelihood catastrophic events is
> a great argument, but global warming would tend to help against some
> low likelihood catastrophic events (in particular anything related to
> more aerosols in the air, from limited regional nuclear warfare to
> asteroid swarms and an unexpected upsurge in volcanic activity).
>
> It does not seem a priori clear to me that a little global warming
> pushes the system towards a state, where "catastrophe" is more likely.
>
>
> >
>
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