If the timetable for exactly when countries need to reduce their greenhouse gas emissions has always seemed a little vague to you, well, we just got a deadline: 2100. That's according to a new report by the United Nations' Intergovernmental Panel on Climate Change, an international organization of scientists dedicated to studying climate change. Using data from previous reports, the 116-page "Synthesis Report" warns global greenhouse emissions need to drop to zero by 2100 to avoid irreversible damage to our planet's atmosphere. Full transcript >>