Tens of thousands of people demonstrated Saturday in 30 cities across the globe to call on world governments to do more to halt global warming. The largest protests took place in Montreal which is hosting the UN Climate Change Conference — the largest international conference ever on global warming. In London environmentalists held banners declaring President Bush to be wanted “for crimes against the planet.” In Washington, drivers of hybrid cars circled the White House. And in New Orleans, residents held a “Save New Orleans, Stop Global Warming” party in the French Quarter. On Saturday environmental groups presented a petition signed by 600,000 Americans urging President Bush to do more to stop global warming. The Bush administration has rejected the Kyoto Protocol to limit greenhouse gases. The United States emits 25 percent of the world’s greenhouse gases even though it has just five percent of the world’s population.