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FILE - In this Dec. 1, 2011 file photo, a cow tries to eat from a dried out cactus on a field near the city of Torreon, Mexico. Mexico is seeing the worst drought since 1941, when the country began recording rainfall. From Chile to Colombia to Mexico, Latin America has been battered recently by wildfires, floods and droughts. While leading climate scientists are unable to pin any single flood or heat wave solely on climate change, experts say the number of extreme weather events is increasing worldwide and the evidence suggests global warming is having an impact. (AP Photo/Alberto Puente, File)

FILE - In this Dec. 1, 2011 file photo, a cow tries to eat from a dried out cactus on a field near the city of Torreon, Mexico. Mexico is seeing the worst drought since 1941, when the country began recording rainfall. From Chile to Colombia to Mexico, Latin America has been battered recently by wildfires, floods and droughts. While leading climate scientists are unable to pin any single flood or heat wave solely on climate change, experts say the number of extreme weather events is increasing worldwide and the evidence suggests global warming is having an impact. (AP Photo/Alberto Puente, File)

Global warming

Global warming is leading to such severe storms, droughts and heat waves that nations should prepare for an unprecedented onslaught of deadly and costly weather disasters, an international panel of climate scientists said in a report issued earlier this year.