Scenario assumptions can be found in chapter 9 of the book "Ecosystems and Human Well-being":
Alcamo J, Van Vuuren DP, Cramer W (2005) Change in Ecosystem Services and Their Drivers across the Scenarios. in Carpenter SR, Pingali P, Bennett EM, Zurek MB (eds.) Ecosystems and Human Well-being. Scenarios, Volume 2. Island Press, Washington.