USA Today: Eight billion? 9 billion? How about 11 billion? No, that’s not the number of bedbugs in a typical New York City hotel, but rather some guesstimates on the number of people that will be here on Earth in the year 2050, up from today’s nearly 7 billion. How will all these extra people affect climate change? A new study out today in the Proceedings of the National Academy of Sciences shows how these changes in the world’s population growth – along with aging and urbanization …