1. Department of Earth and Atmospheric Sciences; University of Nebraska; Lincoln NE USA
2. NASA Goddard Institute for Space Studies; 2880 Broadway New York NY 10025 USA
3. Center for Climate Systems Research; Columbia University; 2880 Broadway New York NY 10025 USA
4. Department of Physical Geography, Faculty of Geosciences; Utrecht University; Heidelberglaan2 3584 CS Utrecht The Netherlands
5. International Institute for Applied Systems Analysis; Schlossplatz 1 A-2361 Laxenburg Austria