On 2/6/07, Gareth <[EMAIL PROTECTED]> wrote:
>
>
> Take a look at Figure SPM-5 in the SPM - AOGCM projections of surface
> temperatures. For the period 2020-29 there is very little difference
> in projected temperature rise (from 1980-99) between the three
> scenarios illustrated (B1, A1B, A2). The SPM says "Best-estimate
> projections from models indicate that decadal-average warming over
> each inhabited continent by 2030 is insensitive to the choice among
> SRES scenarios, and is very likely to be at least twice as large as
> the corresponding model-estimated natural variability during the 20th
> century." My eyeball suggests that the rise is about 0.8C.
>
> I'd like to explore some of the implications of this finding. It
> suggests, for instance, that we have in effect got a "forecast" of
> global average temperature change over the next 25 years. We're
> committed to this warming whatever we do.
Yup.
I think Roger Pielke argues that since this is the case there is no hurry
in determining a policy. I think "discount rate" economics formalizes that
argument. The problem with this is that it will always be true. Any action
we take will have modest and essentially undetectable output for a couple of
decades at least, and the early decades dominate the economic calculus. It
seems to me that going from there to a conclusion that we should never have
a policy is not sensible.
>From a policy perspective,
> we therefore have a known challenge to meet (even if we don't/can't
> know the full implications of that 0.8C). Adaptation is required, and
> to enable us to plan effective adaptation, we will have to work on
> refining projections (both regionally and globally) of near-term
> (10-20 year) change. I know that some work is being done on using
> AOGCMs as seasonal forecast tools at the Hadley Centre - but is this
> seen as an important research focus? It strikes me that this is one
> area with huge policy relevance.
Seasonal forecasting is pretty different from policy time scales. I may be
wrong, but my impression is that GCMs in a dynamic prediction mode (as
opposed to a statistiucal prediction mode) are unlikely to get much
information out beyond a year or two, and such as there would be would only
capture some of the variance associated with the upper ocean.
Do you have a reference? My impression is that this work is more akin to
weather prediction than climate prediction. The models are similar but the
sorts of information we expect to get out of them are very different.
Of course, this doesn't mean that we can afford to ignore mitigation.
> The spread of the red curves (2090-99) in SPM-5 gives a good
> indication of what early action on GHGs might achieve. Policies
> designed to minimise warming by the end of the century are clearly
> essential, but they're not the only game in town. Does the WG2 draft
> reflect this? While the international political community focusses on
> Kyoto-2, are we failing to prepare for the inevitable?
What specific policy actions do you think might be indicated regarding
adaptation on the decadal time scale?
I think this is an interesting question so in the interest of keeping it
going I will venture a bit of more or less uninformed opinion.
I have heard that the Nature Conservancy is pulling back from investments in
littoral ecosystems on the grounds that they are going away anyway. Like
butterflies and pine trees, I think you will find ski resort interests
putting more effort poleward and less at the equatorward end of their range.
The policy question is what sorts of adaptation directly affect public
infrastructure.
Off the top of my head I think this will have more to do with water (and in
some locations with wind) than with temperature. Should countries like the
US and China which span a wide range of climates move their investments
poleward and inland? Or should they buck the trend and shore up the
shoreline and find water for the subtropics?
mt
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