Guardian: The debate about whether to engage China is over – we are now about 20 years into a common-law marriage. The debate about whether China will join the international community also is over. Beijing has been signing up for multilateral forums as if they were going out of style. The great challenge for US secretary of state Hillary Clinton, when she visits Beijing from Friday, is to influence China to play a larger role in preventing global catastrophes in these areas: the economy, nuclear …