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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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