Canwest News Service: Prime Minister Stephen Harper arrived in Japan on Sunday for the Group of Eight summit amid heightened concerns about the struggling global economy and dampened expectations for a breakthrough on climate change. The summit is expected to be dominated by talk about the global economy, which has been hampered by slowing growth as well as soaring oil and food prices. With the economy topping the agenda, G8 officials have been downplaying expectations of tough new commitments on …