Move over, NASDAQ. Watch out, NYSE. Here comes the Chicago Climate Exchange, the nation’s first greenhouse-gas trading program. Announced yesterday by a coalition of corporations and government entities including DuPont, Ford Motor Company, Motorola, and the city of Chicago, the exchange will permit companies to reduce (on paper, at least) their emissions of carbon dioxide and other global warming gases through buying credits earned by firms that surpass emissions-reductions goals. Those participating in the exchange will sign a pledge to reduce emissions over the next four years by 4 percent of their average levels from 1998 to 2002. A similar but mandatory U.S. trading program for acid-rain reductions has met with considerable success, but critics question whether the Chicago Climate Exchange can succeed without nationwide enforceable targets.