Year 2011 has been the tenth warmest year on record, and has likely been warmer than any previous La Nina years. Global tropical cyclone activity was below average in 2011. The La Nina event came to the end in April 2011, and a new event occurred in September 2011. In early 2011, extreme low temperature and cold waves blanketed most Asian and consecutive snow storms hit North America. Severe droughts occurred in West Europe and East China in spring. During summer, eastern Africa suffered the most severe drought since the 1980s, while rain storms and floods raided Southeast Asia, Pakistan and Central and South America. The central type La Nina event, together with the frequent typhoon activities, resulted in the flood in Southeast Asia. And the positive phase of the Indian Ocean Dipole (IOD) may be an important external forcing impacting the flood in Pakistan.