Understanding the regional rise of civilizations by means of a model with effective variables Carsten Lemmen 1 Last change December 23, 2000 1 Working Group Systems Analysis and Modelling SAM, Institute for Chem- istry and Biology of the Marine Environment ICBM, Carl von Ossietzky Univer- sity, Post Office Box 2503, 26111 Oldenburg, Germany, Fax +49 (0)441 798-3484, Tel +49 (0)441 798-5230, mail@carsten-lemmen.de