RIO DE JANEIRO--Scientists have long been warning that extreme weather would cause calamity in the future.... But in South America — which in just the last month has had deadly landslides in Brazil, wildfire in Argentine wetlands and flooding in the Amazon so severe it ruined harvests — that future is already here.In just three hours on Feb.... Global warming is altering the intensity and frequency of extreme weather events, such as El Nino and La Nina, the natural heating and cooling of parts