On Mon, 16 Aug 1999, you wrote:
> Dear Tweeters,
>
> In the attached posting, sent at 08:13 on Aug 15, Jack Bowling
> stated, in part: ..."there is lots of debate about global warming.
> Not whether it is occurring or not- that is IRREFUTABLE [emphasis
> mine]-- but whether it is anthropogenically forced or otherwise"...
> I hesitate to begin a debate on global warming with a professional
> meteorologist like Jack. However, I consider myself an amateur
> climatologist, and I have considerable knowledge of the subject. I
> have a serious problem with the statement above, especially the
> "irrefutable" part.`
(big snip)

In the interests of keeping a non-bird posting short, I would only say
that Wayne has (once again) misrepresented a posting. "Global warming"
has indeed occurred in the past. I offer this short summary on the
case for anthropogenic forcing of the earth's tropospheric temperature
regime:

- ice cores from around the world confirm that the rate of temperature
increase in the 20th century is greater than anytime in the past
6-10,000 years.
- CO2 levels are currently at around 335 ppm by volume and increasing by
1.5-2 ppm per year with most of the increase since the turn of the
century; CO2 is a greenhouse gas that we humans produce in prodigious
quantities.

Many have added these two together to state that humans must be forcing
the ongoing global warming since the current rate of warming is greater
than past records of warming during periods when humans were not
a factor would support. However, as Wayne states, an equal number of
people believe that it is just part of a natural cycle.

Either way, the main case for not just kicking back and enjoying our
upcoming tropical warmth but instead trying to mitigate any human
contribution to the warming trend is such:

- we do not know if there is a critical point of CO2 concentration
beyond which the whole process would accelerate even more than current
rates, i.e., there could be a CO2 flashpoint which would trigger
even more massive rapid warming (and which would lead to rapid
desertification, swamping of coastal cities, death of vegetation by
drought and/or insect damage, etc.).
- given the above, we humans should endeavour to mitigate our
greenhouse gas production.

Nowhere in my original post did I state where I stand on the argument of
anthropogenic forcing of the current global warming, although I did in
a private post to Don B. So for the record, I will state that I
believe that human contribution to overall global warming is likely
only giving a small boost to an otherwise quite natural cycle. It is
mostly our limited geographical time sense that colours our perception
of the event. However, I do believe that consequences of runaway
warming would be catastrophic for our and other species so that
mitigation strategies are the wisest course regardless of whether we
are fouling our own nest.

--
Jack Bowling
jbowling at direct.ca