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Re: Human vs. natural influences on the environment
charliew wrote:
>
> In article <4vn2e4$9h3@igc.apc.org>, tomgray
> <tomgray@igc.apc.org> wrote:
> >brshears@whale.st.usm.edu (Harold Brashears) wrote:
> >>kowens@teleport.com (Jeff Owens) wrote for all to see:
> >>
> >>[edited]
> >>
> >>>There are thousands of subjects we do not have full
> understanding
> >>>of, but that should not stop people from trying.
> Knowledge is
> >>>gained by suggesting a model and then trying to disprove
> it.
> >>>The real issue here is: do we have enough information to
> suggest
> >>>models. The answer from the scientific community is a
> clear YES.
> >>
> >>While I think it is always worth it to build models and to
> test them
> >>(otherwise, I would have been in some other business), I do
> not
> >>believe that means we must act on the output of these
> models at this
> >>time. If you have some reason to believe that the models
> under
> >>discussion are accurate, tell everyone about those reasons.
> >
> >Well, far be it from me to quarrel with anyone's religious
> beliefs.
> >
> >I don't know that a strong belief in models is required,
> though, to
> >simply note that we are clearly changing atmospheric CO2
> concentrations
> >and therefore the earth's energy balance.
>
> Tom,
>
> This is where I continue to disagree with you. We know that
> we are changing the amount of CO2 in the atmosphere.
> However, we don't know if it will keep increasing in
> concentration, and we don't know if there is a threshold
> concentration above which "it is bad". You are making a BIG
> assumption that we are changing the energy balance of the
> earth at this point, because there is no clear documented set
> of measurements that indicate that this is so.
>
What we know by direct observation is that CO_2 levels have increased
siginficantly since the late 50s. We also know by examination of
ice cores that this started at the beginning of the industrial
revolution, and that CO_2 levels remained relatively constant for the
thousand years before that. (This is from the latest Report of
the IPCC Working Group I.) Climate modelers also have a fairly
good idea of how the Carbon cycle works, albeit with some undertainites,
and there is virtually no doubt that the obsrved increase is due
to human activities in burning fossil fuels, cement production, and
changes in land use. As to the future, we can't of course be sure the
models may continue to be explanatory. Unexpected events could occur.
Let us assume that no controls on emissions of fossil fuels are put
in place. Then it is clear that human emissions will grow
exponentially for the next century of so. There are some possibilities
one can envision. Plants might become much more efficient at removing
CO_2 from the atmosphere than they have been until now. Then quite a
bit of the emitted CO_2 might be absorbed by the biosphere. However,
there is no particular reason to believe that will happen. A more
plausible scenario is that Carbon in soils in northern latitudes will be
emitted as temperatures increase, so the level of CO_2 will go up
even faster than it would just by burning of fossil fuels, etc.
Similarly, do you think there is any reason to expect the CO_2 levels
to change sigificantly if we stabilize emissions at current levels?
Why would the Carbon cycle suddenly change its basic structure? Hence,
when you say that we don't know that the CO_2 concentration will keep
increasing, it is right now a pretty good bet. The odds that anything
different will happen on the basis of what we know are very small.
What you suggest is that a very large change may suddenly produce
a sudden and beneficial effect, while keeping things more or less
the way they are may lead to serious problems. Is this really very
plausible? Your experiences in chemical engineering might be
relevant if you chose the right analogy. If you have some elaborate
chemical process and it appears to have been in steady state for a
very long time, making a sudden radical change in its nature and
then arguing that if you didn't, something unexpected might happen
or if you do, something else unexpected, which you have no basis to
predict, might lead to stability seems strange to me. I would think
that in the absence of knowledge, it would be safer to continue the
status quo than to undertake a radical change in the nature of the
process. Moreover, since there is considerable knowledge, emphasizing
that something unexpected might happen doesn't make much sense.
The big problem in talking about this is that people view what is an
enormous physical change in the environment of the earth as the
status quo because it seems not to require significant changes in social
and economic behavior. Hence, most people have it backwards. The
Earth's atmosphere doesn't care if we can continue to live life the
way we want to or not. If we make a radical change in its composition,
even without any emprical evidence, we should consider radical physical
changes a plausible possibility. Given that we have some observational
evidence and considerable theoretical reason to believe this will
have an effect, what we know scientifically suggests caution in
continuing this experiment with our planet. After all, it is the
only planet we have.
--
Leonard Evens len@math.nwu.edu 491-5537
Department of Mathematics, Norwthwestern University
Evanston Illinois
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