Re: [asa] Creation Care

On 1/21/07, David Opderbeck <dopderbeck@gmail.com> wrote:
>
> That is, the community is not in the uncertainty phase since there is a
> framework of understanding that explains the key features of climate for the
> last 420,000 years.
>
> Ok, but that seems very different to me than what I take to be a much bigger
> claim: that the rate of warming can be predicted with any certainty over a
> discrete period of time. If you're saying the community has reached the
> consensus phase on the broad mechanisms of climate change, and part of that
> is that man-made greenhouse gasses speed warming, I wouldn't doubt that.
> But if you're saying the community has reached a consensus that within the
> next century the rate of warming will certainly be X degrees, I would doubt
> that -- or at least, I would question whether that is a meaningful
> consensus, given the uncertainties inherent in the sort of modeling that has
> to be done to make that kind of prediction.

Which is why the scientific community has reached a consensus that
based on a variety of scenarios, models and data sources, the rate of
warming will range from X to Y. Model inputs include different forcing
scenarios (CO2 for instance) as well as different models. The work by
IPCC is actually incredibly thorough in many ways.
See for instance http://www-pcmdi.llnl.gov/ipcc/diagnostic_subprojects.php

See also Wikipedia which reports

<quote>climate sensitivity is 1.5 to 4.5 °C; and the average surface
temperature is projected to increase by 1.4 to 5.8 Celsius degrees
over the period 1990 to 2100, and the sea level is projected to rise
by 0.1 to 0.9 metres over the same period. The wide range in
predictions is based upon several different scenarios that assume
different levels of future CO2 emissions. Each scenario then has a
range of possible outcomes associated with it. The most optimistic
outcome assumes an aggressive campaign to reduce CO2 emissions, while
the most pessimistic is a "business as usual" scenario. The more
realistic scenarios fall in between.
</quote>
>
> A question then: is the consensus more of the former type (broad consenus
> on mechanisms including human produced greenhouse gasses), or is it more of
> the latter type (specific consensus on the extent and effects of
> human-produced warming trend over a discrete period of time)?

Both although the longer the time, the more uncertain the results.

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Received on Sun Jan 21 22:28:59 2007