By JOSEPH COLEMAN Rusutsu (Japan) July 8: Leading industrial nations on Tuesday endorsed halving world emissions of greenhouse gases by 2050, edging forward in the battle against global warming but stopping short of tough, nearer-term targets. The Group of Eight countries, the United States, Japan, Russia, Germany, France, Britain, Canada and Italy, also called on all major countries such as China and India to join in the effort to stem the potentially dangerous rise in world temperatures. "This global challenge can only be met by a global response, in particular, by the contributions from all major economies," the G-8 said in a joint, five-page communiqu