Scientists reported Wednesday that in 10,000 years a massive, worldwide freeze could overcome the planet, more deadly than the Ice Age. British and Canadian researchers said greenhouse gases could prove beneficial in the future to battle a chill that could cover Canada and the United States, Europe and Russia in permanent ice. However, scientists contend the world should not stop fighting global warming, theoretically stoked by human emissions of heat-trapping gases from burning fossil fuels. The research was based on records of tiny marine fossils and the earth's shifting orbit.