I think the climate change discussions have a deeper relevance to the SD
practitioners. While I agree with Tom Fiddamans concerns (and greatly
respect his work on the subject), it misses the point that no one can cla=
im
he/she has THE unique understanding of the CO2 cycle. We do not really
understand the ocean chemistry relative to CO2. We understand an idealize=
d
theory about it. When we attempt a real CO2 balance simulation, I believ=
e
the best simulation still contains a 40% error bar. We do not understand
all the negative (or positive) feedback loops in the system and dont eve=
n
know if the problem is terrestrial or solar or inter-galactic --- I once
heard a non-laughable story based on historical gamma-ray atmospheric
interaction cycles. Therefore, as honest SD practitioners, I think we
would need to make multiple models with multiple viable assumptions and
(hopefully) show that even under these uncertainties, a story, consistent
across all structure assumptions, could be made for (or against) anthropi=
c
CO2 mitigation policies. To simply make "a" model with one view and the=
n
test its uncertainty under policy may still not be "ethical" enough.
G
From: "George Backus" <gbackus@boulder.earthnet.net>
George Backus, President
Policy Assessment Corporation
14604 West 62nd Place
Arvada, Colorado, USA 80004-3621
Bus: +1-303-467-3566
Fax: +1-303-467-3576
Climate Change and SD
-
John Sterman
- Senior Member
- Posts: 117
- Joined: Fri Mar 29, 2002 3:39 am
Climate Change and SD
George Backus is right about the need for multiple models of the climate
change problem (and any other problem for which the uncertainty and stakes
are high).
The implications go beyond what George suggests. In addition to
recognizing that no one model is sufficient, the various models must be
made fully and publicly available for replication, testing, and extension.
Tom Fiddaman has done more in this regard than any other modelers in the
climate arena I am aware of. He carefully replicated the most commonly
cited and used global climate economy models and identified in each a
number of errors and questionable assumptions. For example, many of them
suffer from integration error (DT error). Others, such as the Nordhaus
DICE model, violate conservation of mass (a significant fraction of the
anthropogenic CO2 emissions in that model simply disappear and never show
up in the carbon cycle or anywhere else). I believe these replications are
available on his web site.
John Sterman
J. Spencer Standish Professor of Management
Director, MIT System Dynamics Group
MIT Sloan School of Management
E53-351
30 Wadsworth Street
Cambridge, MA 02142
617/253-1951 (voice); 617/258-7579 (fax), jsterman@mit.edu
http://web.mit.edu/jsterman/www
change problem (and any other problem for which the uncertainty and stakes
are high).
The implications go beyond what George suggests. In addition to
recognizing that no one model is sufficient, the various models must be
made fully and publicly available for replication, testing, and extension.
Tom Fiddaman has done more in this regard than any other modelers in the
climate arena I am aware of. He carefully replicated the most commonly
cited and used global climate economy models and identified in each a
number of errors and questionable assumptions. For example, many of them
suffer from integration error (DT error). Others, such as the Nordhaus
DICE model, violate conservation of mass (a significant fraction of the
anthropogenic CO2 emissions in that model simply disappear and never show
up in the carbon cycle or anywhere else). I believe these replications are
available on his web site.
John Sterman
J. Spencer Standish Professor of Management
Director, MIT System Dynamics Group
MIT Sloan School of Management
E53-351
30 Wadsworth Street
Cambridge, MA 02142
617/253-1951 (voice); 617/258-7579 (fax), jsterman@mit.edu
http://web.mit.edu/jsterman/www