Watson, A., Brovkin, V., Claussen, M., Falkowski, P., Held, H., Payne, A., Rahmstorf, S., Scholes, R., Schrag, D., Sirocko, F., Schellnhuber, H. J. (2004): Group Report: Possible states and modes of operation of the quaternary earth system. - In: Earth system analysis for sustainability. Dahlem workshop report, 189-210.