Guardian: The Prince of Wales is to issue a warning that the world has only “100 months to act” before the damage caused by global warming becomes irreversible. As part of a tour of South America, his speech to business leaders in Rio de Janeiro on Thursday will echo predictions made by climate change experts who believe there are about eight years left to cut C02 emissions. He will warn that failure to act urgently could have catastrophic effects for the planet. The speech will stress …