The Canadian dentist behind what may or may not have been the world’s first global-warming Ponzi scheme either lives or does not live in Iceland. His name is Otto Spork, and when I first learned of him, in 2008, he had secured the water rights to a glacier north of Reykjavík and quit his dental practice to run the most successful hedge fund in Canada. His Toronto investment firm, Sextant Capital Management — the name was chosen to honor his paternal grandfather, Johan Marinus Spork, a Dutch sea captain — had recently been claiming 730 percent returns for its investors. Spork’s…