Maybe you've heard or read somewhere that all kinds of terrible disasters will happen if the (global mean surface) temperature rises just 2⁰C above the pre-industrial level; according to some datasets, we are already more than halfway there.  Further, activists want to lower the threshold to 1.5⁰C  -- thus advancing the date of the “apocalypse.” Note, however, that these same activists never bother to define “mean temperature” or tell you how to measure it -- if indeed that makes sense.  Temperatures vary not only geographically, mainly with latitude and altitude, but also with season, time of day, and weather conditions. Have you ever wondered where the 2⁰C number comes from?  Does it sound like the Y2K scare all over again?  Well, let me tell you, because I have something to do with provoking its original publication.  In 1995, I published an article in Eos, the journal that goes to every member of the American...(Read Full Article)