The Earth Systems Project

Making Global Models Accessible

Global models such as World3, IFs, and Globus are used in many nations' planning and policy making. They discuss, for example, transition to a sustainable demographic and economic future, energy and materials supply, national strategy, and the stability of international political relations. By explicitly incorporating interrelationships known and under investigation by scientists, they provide a quantitative backing for qualitative work by demographers, economists, environmentalists, political scientists, and others. They allow scientists to investigate possible complex interrelationships that would not be evident to those working within a single discipline, since systems of global development and change concern many academic disciplines.

Traditionally global models have been difficult to find and to use. The Earth Systems Project is an attempt to create accessible, understandable versions of important global models. The project was begun in 1989 and continues to a limited degree today.  Information and programs are available for two models. The information is accessible through this Web site. The programs are available for Macintosh computers.  For information on other global models, see Peter Brecke's global models web site, Gottfried Mayer-Kress's global models site, and Barry Hughes' IFs web site.

Beyond the Limits

The Beyond the Limits program uses the "World3" computer model of the book Beyond the Limits. The model and the book investigate possible ways in which world population and industry might approach their carrying capacities, and the likely impacts of possible global policies. The program lets you use the model, change the model, and see the consequences of your changes. The model can help you think about possible world futures, and help you investigate possible effects of global policies. Background information in the program describes how to use the model, diagrams of the model, criticisms of the model, how to get information about it and other global models, and how to learn with it.

Go to Beyond the Limits.

The Gaia Hypothesis & Daisyworld

The Gaia Hypothesis and Daisyworld program lets you use the "Daisyworld" model, which illustrates the Gaia hypothesis that life on Earth affects Earth's global environment. The program includes an introduction; detailed information about the Gaia hypothesis, the model, and criticisms of the model; a simple animated version of the model; and a more detailed version of the model. You can change the model and see the consequences of your changes. Classroom exercises are included.

If you have a Macintosh computer with HyperCard (or the HyperCard Player) 2.1 or newer, you can download The Gaia Hypothesis and Daisyworld (406K) along with its accompanying information. The file you download is in bin-hexed form, so once it is on your computer, you may need to "decode binhex" in a program such as CompactPro or StuffIt. You will be left with a file whose name ends in ".SEA". Just double-click on the file and the program will be ready to use. You may have trouble receiving the file with some web-browsers; if so, you can request a copy by email at the address below.

References for The Gaia Hypothesis & Daisyworld:


The Earth Systems Project is spearheaded by Kenneth L. Simons and Peter J. Poole. Assisting with software development were Michelle Bell, Jennifer Newbury, Kevin Rathbun, Erik Trimble, and Aaron Young. Many people deserve a lot of thanks for their help with the project, involving all aspects including administration, encouragement, feedback, ideas, and testing. Thanks to Hayward Alker, Gerald Barney, Ann Bostrum, Vincent Cate, Sallie Chisholm, Nazli Choucri, Pål Davidson, Joseph Ferreira, Tom Fiddeman, Baruch Fischhoff, Jay Forrester, Allan Heydon, David Kreutzer, Dennis Meadows, John Miller, Marvin Miller, Edward Moriarty, Earll Murman, George Rathjens, Diana Shannon, Jane Sherwin, John Sterman, Ryo Tatsukawa, David White, and David Wood. More information on these people's role is available in the software. Financial supporters included Dennis Meadows and MIT's Departments of Civil Engineering, Political Science, and Urban Studies and Planning; School of Engineering; Center for Global Change Science; and Undergraduate Research Opportunities Program. Computers were provided by MIT's Department of Urban Studies and Planning and the MIT System Dynamics Group. For work by K. Simons: This material is based upon work supported under a National Science Foundation Graduate Fellowship. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author and do not necessarily reflect the views of the National Science Foundation. Any errors or omissions are the responsibility of K. Simons.

A Japanese-language an old version of the Daisyworld program has been developed, and interest has been expressed in creating Japanese and French versions of both programs, but I unfortunately do not have information as to whether these projects have gotten anywhere. If you have more recent information, please contact Ken Simons.

Copyright ©1992-1997 by Kenneth L. Simons.
Revised 31 May 2001