Climate extremes 'key driver' behind rising global hunger: UN José Graziano da Silva, Director-General of the Food and Agriculture Organization of the United Nations (FAO), announces an increase, for the third year, in the number of people experiencing chronic food shortage. The increase in global temperature peaks, and weather hazards such as floods and droughts, are one of the "main causes of serious food crises", according to a report published by five UN agencies. IMAGES AND SOUNDBITES