Innovations Report: Climate change may be one of the most significant threats facing humankind. A new study shows that long-term climate change may ultimately lead to wars and population decline. The study, published November 19 in the early edition of the journal Proceedings of the National Academy of Sciences (PNAS), revealed that as temperatures decreased centuries ago during a period called the Little Ice Age, the number of wars increased, famine occurred and the population declined. Data on …