Americans worried about climate change gathered Saturday for a nationwide day of demonstrations to draw attention to global warming. More than 1,300 events were organized in every state to push the US Congress to require an 80 percent cut in carbon dioxide emissions by 2050. "We see this to be the most pressing issue of our time, and our generation," said Will Bates, 23, one of six former Middlebury College students who helped organize the Step It Up 2007 national event with author Bill McKibben, who was among the first to write about global warming in his 1989 book "The End of Nature." Scientists say a projected 10-foot (three-meter) rise in the ocean level caused by the melting of polar ice caps and glaciers eventually will flood parts of New York City's downtown financial district and other low-lying coastal areas. But estimates vary. The Intergovernmental Panel on Climate Change has projected that ocean levels will rise 7 inches (17.7 centimeters) to 23 inches (58.4 centimeters) this century.