National Geographic: Climate change "tipping points" could be sudden and surprising, experts say. The threat of sudden climate change disaster-from the poles melting to farmlands failing-is real and requires an early warning system, an expert panel suggested on Tuesday. Looking at "tipping points" for global warming disasters, the National Research Council panel report on "abrupt" climate impacts finds noteworthy risks of sharp, sudden sea-level rise, water shortages, and extinctions worldwide in coming years and decades....