MARK STEYN TESTIFIES: Powerline’s covering it and I’m glad it is. Climate activist Michael Mann is suing Steyn for defamation based on a post Steyn wrote for the National Review’s blog. Steyn called Mann’s outrageous global warming hockey stick graph a fraud. I’ve been following this case for years, with great interest. It’s dragged on for over eight years — Mann filed it in 2012. John Hinderaker’s Powerline post has the relevant history as well as an update and links.