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.
It all depends on what you mean by "global warming". If you mean
simply that average temperatures have been significantly increasing in
many parts of the Northern Hemisphere over the last 50 to 100 years,
that is undeniable. However, if by "global warming" you mean a
permanent, non-cyclic trend of increasing temperatures worldwide (or
even in the North Temperatue Zone), particularly a trend resulting
from man-caused environmental changes, that is far from proven.
As Jack himself notes, we do not have reliable climatic records
that go back more than 200 years (or in most parts of North America,
more than 100 years). How can we be sure that the current temperature
trends are not part of a cycle of change with a periodicity of 500
years or more, or even a mainly random series of events?. For example,
there is considerable palaeontological evidence for a so-called
"Hypsithermal" period, since the last Ice Age (i.e., within the last
10,000 years), when temperatures were considerably warmer than they
are now, and many species of plants and animals occurred farther north
than they do today. (I forget the approximate timespan of the
Hypsithermal; maybe one of you can inform us.) The Hypsithermal period
surely resulted from non-human causes, and the current minor
temperature increase could be the start of a contemporary Hypsithermal
period, with man-made changes being a very minor contributing factor.
I don't disagree with the abundant data which show that large
cities are often 1-3 degrees C warmer than their surroundings
(sometimes more), especially in winter. However, it is easy to
overlook the fact that most weather stations are located in or near
cities, and to be fooled into thinking that an increase in
temperatures in cities equates to a worldwide increase in
temperatures. In a country like Canada, cities make up a very tiny
percentage of the landscape.
At the same time, I accept the arguments I have read that a major
increase in CO2 levels in the atmosphere (to 2 or 3 times the 1850
level)
would cause a significant and permanent worldwide increase in
temperature, above the levels caused by changes in other factors. We
should make every effort to minimize emissions of CO2, as well as
other atmospheric pollutants. However, I find no convincing evidence
that the increase in CO2 that has occurred so far (less than 50% over
base levels) is responsible for temperature increases observed during
the 20th century. Global warming, as I see it, is a serious potential
threat in the future, not a demonstrated fact in terms of what has
happened so far.
There have been quite a few major changes in bird distribution in
North America. It seems to me that there are many more cases of major
northward range expansion than of southward range expansion. (Perhaps
someone has done a study of this, and has tallied the number of
species expanding in each direction; if so, I would appreciate a
reference.) This might be taken as evidence of "global warming".
However, the ranges-- at least the breeding ranges-- of most bird
species depend more on habitat (which is affected by climate) than by
climate per se. Changes in the distribution of vegetation types-- a
northward march of "vegetation belts", which apparently did happen
during the Hypsithermal-- would require many decades or even centuries
of significant temperature change to take place. Keep in mind that
most forest types take 200 years or more to mature, let alone for one
forest type to replace another. Most of the changes in bird
distribution that we have seen are most easily explained by factors
other than climate-- such as habitat changes caused by non-climatic
factors (e.g. clearing of forests, cultivation of the Prairies),
spread of introduced species, etc.
Jack, I believe you are guilty of misleading some of our
subscribers by jumping on the bandwagon that states that "global
warming" is an established fact in terms of what has happened to date.
The definition of "global warming" is critical here, and it may be
that this is just another debate about semantics.
If any of my statements above are questionable or fallacious, I
would appreciate readers pointing out published articles that support
alternative viewpoints. The subject of global warming is a contentious
and fascinating one, and my mind remains open to alternative
explanations.

Wayne C. Weber
114-525 Dalgleish Drive
Kamloops, B.C. V2C 6E4
Phone: (250) 377-8865
wayne_weber at bc.sympatico.ca



-----Original Message-----
From: Jack Bowling <jbowling at direct.ca>
To: tweeters at u.washington.edu <tweeters at u.washington.edu>
Date: Sunday, August 15, 1999 8:13 AM
Subject: Re: Birds and global warming


>Rob wrote:
>
>> >a couple of weeks ago, I heard the leader to a piece on NPR, the
gist of
>> >which was that birds are good indicators of global warming; i.e.,
as the
>> >climate warms, birds will find suitable habitat in more northerly
areas
>> >that would previously have been inhospitable. This may help
explain the
>> >northward range expansion of scrub jays and grackles, for
instance, and
>> >maybe such oddities as little blue herons in the Bay Area, or
summer
>> >tanagers in Sacramento. I didn't, unfortunately, hear the whole
piece,
>> >which typically would have included someone with an opposing or
alternate
>> >viewpoint. Anyone have any critiques of this theory? Know of any
published
>> >references on this topic? Thanks...
>
>then Don answered -
>
>> I know there's been some published work on the average departure
>> and arrival time of raptors in eastern Canada over the past
>> two ?I think? decades. I've not read the paper(s) myself, have
just
>> seen references...
>>
>> The gist of it is that they've been arriving and nesting earlier,
>> and it's statistically significant (obviously, there's annual
>> variation which must be taken into consideration).
>>
>> Such correlations might be related to global warming, might be
>> due to other causes, but as more and more of them are discovered
>> and as work is done which ties down causes when possible, I'd
>> be very, very surprised if the case for global warming were in
>> any way weakened...
>
>Check out any of the *.meterology.* usenet lists and you will see
that there
>is lots of debate about global warming. Not whether it is occurring
or not -
>that is irrefutable - but whether it is anthropogenically forced or
otherwise.
>The problem we humans have is that our observational period of record
is
>measured in a couple of hundred years which is the blink of an eye in
>geophysical terms, thus our comparative analyses lack good data.
>
>As for birds taking advantage of global warming, I think there is
plenty of
>evidence for the fact that birds will colonize any habitat that suits
them.
>Lazuli Buntings and Willow Flycatchers have been pressing northward
steadily
>through BC the past decade. The population to the south is far from
saturated so
>I doubt that it is due to territorial expansion pressures.
>
>
>
>
>
>==========================
>Jack Bowling
>Prince George, BC
>jbowling at direct.ca
>