Climate Central: The Arctic has seen warmer summers over the past two decades than at any time in the past 600 years, according to a study published this week in the journal Nature. The study uses a sophisticated statistical approach, known as Bayesian modeling, to show that the extremely warm summers in high northern latitudes are evidence of an overall warming trend, rather than just a temporary fluctuation in an otherwise unchanging climate. Thats a crucial distinction: a natural fluctuation might reverse before...