Reuters: California, which enjoyed widespread praise this week for its ambitious plan to combat global warming, now faces the tough part: making it work. On Thursday, the most populous US state unveiled a plan to reduce greenhouse gas emissions to 1990 levels over the next 12 years with requirements for cleaner cars, more solar and wind energy and stringent caps on big polluting industries. But the state gave no estimate for the sweeping program’s cost except to say that it was …