Hi again Chris,
What you've written below is very helpful. In some ways we're back
to the fundamental issue of the various strengths and weaknesses of
models, no? which applies both to the economic models as well as to
the climate models.
>At 11:49 24/05/2002 -0500, Jim wrote:
> >Sorry if I'm just being obtuse, but I am grateful at any rate for
>>your helping me work through these issues and figures.
>>
>>Jim T.
>>
>
>Schneider's point is that even with the footnote, characterising the
>impacts as 'about $5 trillion' gives a misleading impression of precision.
>
>For instance, in a 1996 paper, we reported the result of some model runs as
>showing the 90% confidence interval of the impacts of business as usual
>emissions would be between $4 trillion and $41 trillion, with a mean value
>of $18 trillion. What is more this uncertainty does not include varying the
>discount rate (it assumes a 3% per yer rate of pure time preference). If
>you do the sums at a 0% rate of pure time preference (which some people
>argue is the only ethically defensible rate) the 90% confidence interval of
>the business as usual impacts is $198 trillion to $2058 trillion, with a
>mean value of $921 trillion.
I'm curious what you think of the Nordhaus and Boyer study in
general--especially in light of Lomborg's heavy reliance upon it.
Anyway, thanks for the assessment. Alfred North Whitehead referred
to "the fallacy of misplaced concreteness"--I think the $5 trillion
figure applies.
Jim
>
>We concluded '...in reading any study on the valuation of global warming
>impacts, policy makers are advised to carefully consider the treatment of
>uncertainty as well as assumptions about adaptation to climate change,
>non-linearity in damage as a function of temperature rise, secondary
>benefits to CO2 abatement, and the discount rate. We have shown that these
>assumptions, often hidden in the small print or not reported at all, have a
>profound effect upon the marginal impact calculations' (E L Plambeck and C
>Hope, 'PAGE95, an updated valuation of the impacts of global warming',
>Energy Policy, vol 24, pp 783-793, 1996).
>
>And yes, this uncertainty applies equally to the alternative policies as
>well.
>
>Chris
>
>
>Chris Hope, Judge Institute of Management,
>University of Cambridge, Cambridge CB2 1AG, UK.
>Voice: +44 1223 338194. Fax: +44 1223 339701
>e-mail: [log in to unmask]
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