Proceedings of the 45th Session of the International Seminars on Nuclear War and Planetary Emergencies held in Erice, Sicily. This Seminar has again gathered, in 2012, over one hundred scientists from 43 countries in an interdisciplinary effort that has been going on for the last 31 years, to examine and analyze planetary problems which had been followed up, all year long, by the World Federation of Scientists' Permanent Monitoring Panels.