From: userDHAL@mts.ucs.UAlberta.CA (David Halliwell)
Subject: Re: What is Climate?
Organization: University Of Alberta, Edmonton Canada
Date: Fri, 8 Jan 1993 00:54:25 GMT

eapg137@orion.oac.uci.edu (Bryan Joseph Hannegan) writes:

>In article <dhalliwe.726290141@muskwa.ucs.ualberta.ca> userDHAL@mts.ucs.UAlberta.CA (David Halliwell) writes:
>>
>>(...) figure out how long a period is required to observe all possible
>>variability for a given set of boundary conditions. A "climate change"
>>would be a shift in climate which is attributable to some change in
>>controlling conditions (e.g. solar output, or some aspect of internal
>>conditions which is independent of the climatic variabilty). Thus,
>>variability is the time-dependent behaviour which cannot be attributed
>>to time-dependent controlling factors. If we have incorrectly seperated
>>"variability" and "change", then we may spend a lot of time looking for
>>the cause of "changes" which were in fact "variation" and therefore
>>are "unexplainable".
>>

>     Paleoclimatology seems like a candidate field for these kinds of things.
>Can we really be sure that all the variability can be observed? Must the full
>range of variability be observed before we can surely attribute climate change
>to its rightful forcing mechanism? I'm pessimistic concerning ideas like these,
>since I am not sure that the wide range of variability will ever be experienced
>for a single set of static boundary conditions, much less the continually
>changing and dynamic boundary conditions that exist today.

   I was going to try to edit the above a bit, but then decided it was
best to leave it all to provide context. Bryan's point brings up another
issue in terms of "understanding climate". (i.e. I'm going to avoid the
problem by changing the subject :-)). The "classic" definition of climate
- averaging observations - is a purely descriptive approach, and suffers
from the limitation that we can never be sure that we have seen everything,
as Bryan pointed out. In order to truly "understand" climate, we must
take an analytical approach, to resolve the reasons for the patterns
that we observe.

   One of the fun areas (at a hobbyist level) for me is the concept of
chaotic systems. This is where an approach of saying 'that was quite
a shift! What "caused" it?' could be very misleading. If we truly
understand the mechanisms of the climate system, we could predict
the possibility of variations which have not yet been observed.
The "surprise" ones would then be the ones that were really caused by
some shift in controlling factors.


>     The definition I received in my undergrad years lead me to believe that 
>climate is simply "average weather", including all the extremes and midpoints.
>A little narrow, I agree, but for me this suffices, since it leaves vague
>the more specific points of "over how long of a time, and how big of an area?".
>Climate change studies, like those we do at UC Irvine, revolve around the 
>shifts that can be attributed to something outside of the system (like Dave
>mentioned above), and as such, for the purposes of our inquiry, the definition
>of climate we use can be safely redefined to best express the changes we find,
>for the definition can vary without disturbing the study. A lot of the work 
>on climate change I have come into contact with has a similar feature.

   I would be interested in hearing from more people in terms of their
backgound: from what discipline have they derived their "working definition"
of climatology. I come from a physical geography background, and was
taught about climatology from the perspective of the global environment:
linkages between the atmosphere, biosphere, etc. Here at the University
of Alberta we also have a Division of Meteorology. One or two of the
meteorology people here with a strictly meteorological background seem
to have more of a "climatology is statistics applied to meteorology"
viewpoint.

   When I was hired here, there was apparently quite a bit of discussion
as to what type of "climatologist" the department wanted. The met people
were in favour of a statistical-meteorologist type, while the geographers
were in favour of an environmental/field-oriented type. Fortunately for
me, the geographers won :-). [What they got was a permafrost scientist
who got interested in climatology because frozen soils are associated
with cold climates.]

   There is still one meteorologist in this department that seems to
have a hard time understanding that I teach more than Koppen's climate
classification system in my climatology courses. :-(

>     I'll definitely chew on this some more.

   Tasty, ain't it?


Dave Halliwell
Department of Geography
University of Alberta
Edmonton, Alberta
Newsgroups: sci.environment