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Re: fHuman vs. natural influences on the environment
My discussion was intended to be more in the line of human
influences on the environment rather than natural influences
on it. At this point, I have been flogged by people who have
come up with several possible scenarios that I accept as
plausible. I wish I had been more explicit in my original
comments. However, I still maintain that the human influence
on the environment has been small (perhaps almost
immeasureable) to date. The biggest problem here regards the
fact that we don't have a good idea of what normal
variability is, so it's difficult to know if humans have
caused a measureable change. If there is someone out there
who strongly disagrees, please provide a few statistics to
indicate that we are seeing a statistically significant
disturbance. In other words, if the standard deviation of
the global average temperature is 1 deg F, a statistically
significant disturbance should be approximately 2 standard
deviations from the "norm" (approximately 2 deg F).
Regarding the large fresh water lake that caused a 10 deg F
drop in the earth's temperature, there has to be more to the
story than this. An energy balance around the earth would
imply that no temperature change should have been seen.
Thus, some factor should have resulted in a sizeable change
to the amount of solar radiation reaching the ground, or in
the absorptive characteristics of the atmosphere for this to
occur. I am a bit skeptical of the conclusions of this
documentary but not necessarily skeptical of the evidence for
global cooling. In other words, I am not saying that global
cooling didn't happen in this time frame - it is likely that
the conclusions were drastically over-simplified regarding
the cause of the cooling.
In article <01bb8876$212c7220$1893aec7@home>,
"Rick & Bea Tarara" <rbtarara@sprynet.com> wrote:
>In the James Burke film "After the Warming" considerable
reference is made
>to an event in Canada about 10,000 years ago. A pent up
fresh water lake
>broke free (after the ice dams that held it in place
broke/melted) and
>flooded the North Atlantic with fresh water. The effect on
the Gulf Stream
>was such to cool the earth--by 10 Degrees (I assume
Fahrenheit) in the
>space of ONLY 100 years. The evidence for this is primarily
from ice cores
>(and sorry I have no more solid references). The point made
in the film
>(which also chronicles other historical climatic changes) IS
that large
>temperature swings CAN happen in essentially a human
life-time. Another
>point in the film (the second half of which is a Global
Warming scenario
>using WORSE-CASE physical predictions and probably BEST-CASE
political
>reaction--and hence is VERY open to criticism) is that the
great
>uncertainty/lack-of-knowledge in the feedback responses of
the oceans is
>the Joker in the Global Warming game. Burke's conclusions,
and the one
>that I interpret as that of the 'third-group' types, is that
it would
>simply be prudent to start looking NOW at ways to reduce
fossil fuel use.
>This makes even more sense when faced with the other
'negative aspects' of
>such use such as economic dependence, acid-rain,
air-pollution, finite
>reserves, etc. In the film scenario, carbon emissions are
cut by 50% by
>2050 (with considerable warming happening anyway--to spur on
such a
>reduction). The time table is adjustable but IMO, the
concept is
>sound--take out some insurance now by starting a slow but
steady program of
>reductions in carbon emissions.
>
>Rick Tarara
>
>charliew <charliew@hal-pc.org> wrote in article
><4ugjcq$6sc_001@pm5-42.hal-pc.org>...
>> Admittedly, there are events which have altered the
>> atmosphere's temperature. However, if the probability is
>> almost nil over one lifetime, I do not consider these
events
>> to be particularly relevant. Regarding your statement
that
>> global warming is going to happen over one or two
lifetimes,
>> there are a couple of questions that may impact what we
want
>> to do about it.
>>
>
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