Truthdig: The unprecedented drought now affecting So Paulo, South Americas giant metropolis, is believed to be caused by the absence of the flying rivers-the vapour clouds from the Amazon that normally bring rain to the centre and south of Brazil. Some Brazilian scientists say the absence of rain that has dried up rivers and reservoirs in central and southeast Brazil is not just a quirk of nature, but a change brought about by a combination of the continuing deforestation of the Amazon and global warming....