Niall Ferguson, a professor of political and financial history at the University of Oxford, writing in the New York Times (free reg req'd yadda yadda) says that there are four important trends that will shape the early 21st century:

• The globalization of terrorism.
• The approach of a second energy crisis.
• The formalization of American imperialism.
• The fragmentation of the multicultural polity. (Civil wars, breakup of countries on ethnic and racial lines, as happened in Kosovo and Rwanda)