Press Association: US president George Bush has said China and India must sign up to measures to reduce greenhouse gas emissions in order to achieve a global agreement to combat climate change. Global warming, along with soaring fuel prices and African aid, will be among the topics discussed at the G8 summit in northern Japan. G8 leaders face major differences over how far to go in trying to set limits on pollutants that contribute to climate change. The host of this year’s G8 summit, …