National Geographic: The planet is hotter now than it has been for nearly the past 2,000 years, researchers report. The new study is led by Michael Mann, a climatologist who helped develop the famous 1998 “hockey stick” graph–a reconstruction of Northern Hemisphere temperatures over the past thousand years showing a sharp uptick beginning around 1900. In their new work, Mann and colleagues back up the hockey stick graph by citing other temperature indicators in the natural record. The …