Volume 5, Number 30: 24 July 2002 The query imbedded in the title of this week's Editorial is borrowed from a provocative new paper that suggests humanity should have some idea of the answer to this question before we rush headlong into adopting expensive and economy-wrenching measures to battle what could well turn out to be an imaginary enemy. The author - C.J. van der Veen of the Byrd Polar Research Center at Ohio State University - puts it this way: "for purposes of formulating policies, some of which could be unpopular or costly, it is imperative that probability density...