Mitt Romney and Alan Keyes describe what impact they believe global warming has on the American economy. --- Iowa Public Television broadcast "The Des Moines Register Presidential Debates" live from the Iowa Public Television Maytag Auditorium in Johnston Iowa on December 12, 2007. This forum featured nine of the Republican candidates for President: Ambassador Alan Keyes; former New York Mayor Rudy Giuliani; former Arkansas Gov. Mike Huckabee; California Rep. Duncan Hunter Arizona Sen. John McCain; Texas Rep. Ron Paul; former Massachusetts Gov. Mitt Romney; Colorado Rep. Tom Tancredo; and former Tennessee Senator Fred Thompson. For more information visit "The Des Moines Register Presidential Debates" on Iowa Public Television. http://www.iptv.org/campaign08