The demonstrations are planned to coincide with the 10-day U.N. Climate Change Conference being held in Montreal to review and update the Kyoto Protocol, the global accord that binds the top 35 industrialized nations to lower greenhouse gas emissions.
The largest march was expected in downtown Montreal, though others are planned in more than 30 countries and in about 40 cities in the United States.
In Washington, drivers of hybrid cars plan to rally around the White House. In New Orleans, residents intend to hold a "Save New Orleans, Stop Global Warming" party in the French Quarter. Other events will be held from Boston to Los Angeles.
Five environmental groups, including Greenpeace and the Climate Crisis Coalition, intend to deliver a petition signed by 600,000 Americans to the U.S. Consulate in Montreal urging the Bush administration and the U.S. Congress to help slow global warming.
President George Bush has been widely criticized for pulling out of the Kyoto Treaty, instead calling for an 18 percent reduction in the U.S. growth rate of greenhouse gases by 2012 and committing $5 billion a year to global warming science and technology.
The United States, which spews out nearly 25 percent of the world's carbon emissions, will likely be the focus of the demonstrations and marches worldwide.
Health experts at the U.N. Climate Change Conference said Friday that global warming is responsible for as many as 150,000 deaths annually around the world.
Canadian Inuit of the isolated Arctic north have traveled to Montreal to take part. Indian leader Jose Kusugak told The Associated Press that he brought along hunters, trappers and elders to reassure them that people from the south were not indifferent to their plight.
"It was important to show there are a lot of people in the world who care," he said.