WASHINGTON — Putting his prestige on the line, President Barack Obama will personally commit the U.S. to a goal of substantially cutting greenhouse gases at next month's Copenhagen climate summit. He will insist America is ready to tackle global warming despite resistance in Congress over higher costs for businesses and homeowners. Obama will attend the start of the conference Dec. 9, a week from next Wednesday, before heading to Oslo to accept the Nobel Peace Prize. He will "put on the table" a U.S. commitment to cut emissions by 17 percent over the next decade, on the way to reducing...