What started out as a moderate global warm-up about 55 million years ago triggered a massive injection of greenhouse gases into the atmosphere that sent temperatures skyrocketing, a new study says. The finding suggests that today's temperature rise may just be priming the planet for a carbon belch of epic proportions."You've got these feedbacks, these chain reactions of events in the atmosphere-ocean system," said Appy Sluijs, a paleoecologist at Utrecht University in the Netherlands. Sluijs and his colleagues found evidence for the chain reaction in two sections of sediment that accumulated on an ocean floor in what is now New...